Main Fundamentals of Building Construction: Materials and Methods
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JWBK274_Allen_Appendix.indd 958 10/30/08 5:32:05 AM Fundamentals of Building Construction JWBK274_FM.indd i 10/30/08 5:41:36 AM JWBK274_FM.indd ii 10/30/08 5:41:37 AM Fundamentals of Building Construction Materials and Methods FIFTH EDITION Edward Allen and Joseph Iano John Wiley & Sons, Inc. JWBK274_FM.indd iii 10/30/08 5:41:41 AM Frontispiece: World Trade Construction site, 2008. Photo by Andrew Watts. This book is printed on acid-free paper. Copyright © 2009 by John Wiley & Sons. All rights reserved Published by John Wiley & Sons, Inc., Hoboken, New Jersey Published simultaneously in Canada No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning, or otherwise, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 646-8600, or on the web at www.copyright.com. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, (201) 748-6011, fax (201) 748-6008, or online at www.wiley.com/go/permissions. The drawings, tables, descriptions, and photographs in this book have been obtained from many sources, including trade associations, suppliers of building materials, governmental organizations, and architectural firms. They are presented in good faith, but the authors, illustrators, and publisher do not warrant, and assume no liability for, their accuracy, completeness or fitness for any particular purpose. It is the responsibility of users to apply their professional knowledge in the use of information contained in this book, to consult the original sources for additional information when appropriate, and to s; eek expert advice when appropriate. The fact that an organization or Website is referred to in this work as a citation and/or a potential source of further information does not mean that the authors or the publisher endorses the information the organization or Website may provide or recommendations it may make. Further, readers should be aware that Internet Websites listed in this work may have changed or disappeared between when this work was written and when it is read. For general information about our other products and services, please contact our Customer Care Department within the United States at (800) 762-2974, outside the United States at (317) 572-3993 or fax (317) 572-4002. Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books. For more information about Wiley products, visit our web site at www.wiley.com. Library of Congress Cataloging-in-Publication Data: Allen, Edward, 1938Fundamentals of building construction : materials and methods / Edward Allen, Joseph Iano. -- 5th ed. p. cm. ISBN 978-0-470-07468-8 (cloth) 1. Building. 2. Building materials. I. Iano, Joseph. II. Title. TH145.A417 2008 629--dc22 2008036198 Printed in the United States of America 10 9 8 7 6 5 4 3 2 1 JWBK274_FM.indd iv 10/30/08 5:41:41 AM Contents Preface to the Fifth Edition xi Trends in the Delivery of Design and Construction Services 22 Recurring Concerns 23 2 1 Making Buildings 3 Learning to Build 4 Sustainability 4 The Work of the Design Professional: Choosing Building Systems 8 Construction Standards and Information Resources 15 The Work of the Construction Professional: Constructing Buildings 16 Foundations 29 Foundation Requirements 30 Foundation Settlement 30 Earth Materials 31 Considerations of Sustainability in Site Work, Excavations, and Foundations 38 Excavation 38 Foundations 52 Underpinning 66 Retaining Walls 68 Geotextiles 71 Waterproofing and Drainage 72 Basement Insulation 77 Shallow Frost-Protected Foundations 77 Backfilling 77 Up–Down Construction 78 Designing Foundations 79 Foundation Design and the Building Codes 80 3 Wood 85 Trees 86 Considerations of Sustainability in Wood Construction 90 v JWBK274_FM.indd v 10/30/08 5:41:42 AM vi / Contents Lumber 92 Wood Products 102 A Naturally Grown Building Material 106 Plastic Lumber 106 Wood Panel Products 107 Wood Chemical Treatments 115 Wood Fasteners 117 Manufactured Wood Components 124 Types of Wood Construction 127 FROM CONCEPT TO REALITY 131 An Enclosure for a Residential Swimming Pool 4 Heavy Timber Frame Construction 135 Fire-Resistive Heavy Timber Construction 140 Considerations of Sustainability in Heavy Timber Construction 141 Combustible Buildings Framed with Heavy Timber 149 Lateral Bracing of Heavy Timber Buildings 149 Building Services in Heavy Timber Buildings 149 Longer Spans in Heavy Timber 150 For Preliminary Design of a Heavy Timber Structure 156 Heavy Timber and the Building Codes 156 Uniqueness of Heavy Timber Framing 156 5 Wood Light Frame Construction 161 History 163 Platform Frame 164 Considerations of Sustainability in Wood Light Frame Construction 166 Foundations for Light Frame Structures 166 JWBK274_FM.indd vi Building the Frame 175 Variations on Wood Light Frame Construction 209 For Preliminary Design of a Wood Light Frame Structure 212 Wood Light Frame Construction and the Building Codes 212 Uniqueness of Wood Light Frame Construction 214 6 Exterior Finishes for Wood Light Frame Construction 221 Protection from the Weather 222 Roofing 222 Windows and Doors 230 Paints and Coatings 234 Siding 238 Corner Boards and Exterior Trim 248 Considerations of Sustainability in Paints and Other Architectural Coatings 250 Exterior Construction 251 Sealing Exterior Joints 251 Exterior Painting, Finish Grading, and Landscaping 252 7 Interior Finishes for Wood Light Frame Construction 255 Completing the Building Enclosure 263 Wall and Ceiling Finish 273 Millwork and Finish Carpentry 273 Proportioning Fireplaces 274 Proportioning Stairs 288 Flooring and Ceramic Tile Work 290 Finishing Touches 292 10/30/08 5:41:45 AM Contents / vii Spanning Systems for Masonry Bearing Wall Construction 386 Detailing Masonry Walls 390 Some Special Problems of Masonry Construction 395 Movement Joints in Buildings 396 Masonry and the Building Codes 404 Uniqueness of Masonry 405 11 8 Brick Masonry 297 History 298 Mortar 301 Considerations of Sustainability in Brick Masonry 304 Brick Masonry 304 Masonry Wall Construction 327 9 Stone and Concrete Masonry 337 Stone Masonry 338 Considerations of Sustainability in Stone and Concrete Masonry 350 Concrete Masonry 358 Other Types of Masonry Units 368 Masonry Wall Construction 368 10 Masonry Wall Construction 377 Types of Masonry Walls 378 For Preliminary Design of a Loadbearing Masonry Structure JWBK274_FM.indd vii 386 Steel Frame Construction 411 History 412 The Material Steel 414 For Preliminary Design of a Steel Structure 417 Details of Steel Framing 431 The Construction Process 441 Fireproofing of Steel Framing 459 Longer Spans in Steel 464 Fabric Structures 472 Composite Columns 476 Industrialized Systems in Steel 476 Considerations of Sustainability in Steel Frame Construction 477 Steel and the Building Codes 478 Uniqueness of Steel 478 12 Light Gauge Steel Frame Construction 489 The Concept of Light Gauge Steel Construction 490 Consider ations of Sustainability in Light Gauge Steel Framing 491 Framing Procedures 492 Other Common Uses of Light Gauge Steel Framing 499 For Preliminary Design of a Light Gauge Steel Frame Structure 502 10/30/08 5:41:47 AM viii / Contents Advantages and Disadvantages of Light Gauge Steel Framing 502 Light Gauge Steel Framing and the Building Codes 503 Finishes for Light Gauge Steel Framing 503 Metals in Architecture 505 FROM CONCEPT TO REALITY 510 Camera Obscura at Mitchell Park, Greenport, New York 13 15 Concrete Construction 515 History 516 Cement and Concrete 517 Considerations of Sustainability in Concrete Construction 520 Making and Placing Concrete 524 Formwork 528 Reinforcing 529 Concrete Creep 544 Prestressing 544 Innovations in Concrete Construction 548 ACI 301 550 14 Sitecast Concrete Framing Systems 553 Casting a Concrete Slab on Grade 555 Casting a Concrete Wall 560 Casting a Concrete Column 565 One-Way Floor and Roof Framing Systems 567 Two-Way Floor and Roof Framing Systems 575 Concrete Stairs 581 Sitecast Posttensioned Framing Systems 581 Selecting a Sitecast Concrete Framing System 583 Innovations in Sitecast Concrete Construction 583 For Preliminary Design of a Sitecast Concrete Structure 586 JWBK274_FM.indd viii Architectural Concrete 589 Cutting Concrete, Stone, and Masonry 593 Longer Spans in Sitecast Concrete 598 Designing Economical Sitecast Concrete Buildings 601 Sitecast Concrete and the Building Codes 601 Uniqueness of Sitecast Concrete 602 Precast Concrete Framing Systems 611 Precast, Prestressed Concrete Structural Elements 614 For Preliminary Design of a Precast Concrete Structure 615 Assembly Concepts for Precast Concrete Buildings 616 Manufacture of Precast Concrete Structural Elements 617 Joining Precast Concrete Elements 623 Fastening to Concrete 624 The Construction Process 638 Precast Concrete and the Building Codes 638 Considerations of Sustainability in Precast Concrete Construction 639 Uniqueness of Precast Concrete 643 10/30/08 5:41:48 AM Contents 18 Windows and Doors / ix 747 Windows 748 Plastics in Building Construction 758 Considerations of Sustainability Relating to Windows and Doors 769 Doors 769 Safety Considerations in Windows and Doors 775 Fenestration Testing and Standards 775 16 19 Roofing 651 Low-Slope Roofs 653 Building Enclosure Essentials: Thermal Insulation and Vapor Retarder 658 Steep Roofs 678 Considerations of Sustainability in Roofing 692 Sustainable Roofing 693 Roofing and the Building Codes 697 Building Enclosure Essentials: Dissimilar Metals and the Galvanic Series 698 17 Glass and Glazing 707 History 708 The Material Glass 710 Considerations of Sustainability Relating to Glass 712 Glazing 724 Glass and Energy 736 Glass and the Building Codes 738 FROM CONCEPT TO REALITY 742 Skating Rink at Yerba Buena Gardens, San Francisco JWBK274_FM.indd ix Designing Exterior Wall Systems 783 Design Requirements for the Exterior Wall 784 Considerations of Sustainability in Exterior Wall Systems 789 Conceptual Approaches to Watertightness in the Exterior Wall 790 Sealant Joints in the Exterior Wall 795 Basic Concepts of Exterior Wall Systems 799 Building Enclosure Essentials: Air Barrier 800 Curtain Wall Testing and Standards 802 The Exterior Wall and the Building Codes 804 20 Cladding with Masonry and Concrete 809 Masonry Veneer Curtain Walls 810 Stone Curtain Walls 817 Precast Concrete Curtain Walls 822 Exterior Insulation and Finish System 828 Future Directions in Masonry and Stone Cladding 832 FROM CONCEPT TO REALITY 834 Seattle University School of Law, Seattle, Washington 10/30/08 5:41:53 AM x / Contents 21 Cladding with Metal and Glass 839 Aluminum Extrusions 840 Considerations of Sustainability in Aluminum Cladding 845 Aluminum and Glass Framing Systems 846 Modes of Assembly 848 The Rainscreen Principle in Metal-and-Glass Cladding 856 Expansion Joints in Metal-and-Glass Walls 862 Sloped Glazing 863 Dual-Layered Glass Cladding 864 Curtain Wall Design and Construction: The Process 866 Considerations of Sustainability in Selecting Interior Finishes 874 Selecting Interior Finish Systems 875 Trends in Interior Finish Systems 879 23 Types of Interior Walls 884 Framed Partition Systems 885 Considerations of Sustainability in Gypsum Products 890 Plaster Ornament 902 Masonry Partition Systems 916 Wall and Partition Facings 916 24 22 Selecting Interior Finishes 869 Installation of Mechanical and Electrical Services 870 The Sequence of Interior Finishing Operations 872 JWBK274_FM.indd x Interior Walls and Partitions 883 Finish Ceilings and Floors 923 Finish Ceilings 924 Types of Ceilings 924 Considerations of Sustainability in Finish Ceilings and Floors 934 Finish Flooring 934 Types of Finish Flooring Materials 940 Flooring Thickness 953 Appendix 956 Glossary 959 Index 989 10/30/08 5:41:58 AM Preface to the F IFTH E DITION First published almost a quarter century ago, Fundamentals of Building Construction: Materials and Methods, now in its fifth edition, has wrought a revolution in construction education. It has been instrumental in making a previously unpopular area of study not merely palatable but vibrant and well liked. It has taken a body of knowledge once characterized as antithetical to design excellence and has made it widely recognized as being centrally relevant to good building design. It has replaced dry, unattractive books with a well designed, readable volume that students value and keep as a reference work. It was the first book in its field to be even-handed in its coverage and profusely and effectively illustrated throughout. It was the first to release the teacher from the burden of explaining everything in the subject, thereby freeing class time for discussions, case studies, field trips, and other enrichments. Gaining a useful knowledge of the materials and methods of building construction is crucial and a necessity for the student of architecture, engineering, or construction, but it can be a daunting task. The field is huge, diverse, and complex, and it changes at such a rate that it seems impossible to ever master. This book has gained its preeminent status as an academic text in this field because of its logical organization, outstanding illustrations, clear writing, pleasing page layouts, and distinctive philosophy: It is integrative, presenting a single narrative that interweaves issues of building science, materials science, legal constraints, and building craft so that the reader does not have to refer to separate parts of the book to make the connections between these issues. Building techniques are presented as whole working systems rather than component parts. It is selective rather than comprehensive. This makes it easy and pleasant for the reader to gain a basic working knowledge that can later be expanded, without piling on so many facts and figures that the reader becomes confused or frightened away from wanting to learn about construction. Reading other texts was once like trying to drink from a fire hose; reading this one is like enjoying a carefully prepared meal. It is empowering because it is structured around the process of designing and constructing buildings. The student of architecture will find that it features the design possibilities of the various materials and systems. Students interested in building or managing the construction process will find its organization around construction sequences to be invaluable. The book is necessarily complex without being complicated. It avoids the dilemma of having to expand ad infinitum over time by presenting the basic construction systems, each in sufficient detail that the student is brought to an operational level of knowledge. It deals, as its subtitle indicates, with fundamentals. We have made many changes in the book between the fourth and fifth editions. Chapter 1 includes new coverage of the role of the construction contractor in the process of making buildings. Included in this section are a discussion of different models and contractual arrangements for the delivery of construction services, the scheduling and management of construction, and evolving trends in the delivery of both design and construction services. A new series of sidebars, Building Enclosure Essentials, is introduced. These treat topics critical to the performance of the building envelope, such as the flow of heat, air, and moisture through the exterior walls and roof. Coverage of sustainable construction and green building rating systems has been updated and expanded, both within the body of the text and within the sidebars xi JWBK274_FM.indd xi 10/30/08 5:42:02 AM xii / Preface to the Fifth Edition dedicated to considerations of sustainability for different materials which appear in almost every chapter. The book tracks a number of trends that are discernable in the building industry: Sustainable design is becoming increasingly mainstream and growing in sophistication. New forms of contractual relationships between the owner, architect, and builder encourage more streamlined and cooperative design and building processes. The materials of construction themselves continue to evolve, with higher strength steel and concrete, high-performance glazing, waste reduction and materials recycling. We continue to expand the book’s use of photorealistic renderings. These figures play an important part in achieving the authors’ goal of making complex building details readily understandable, while also appealing to the eye. We continue to take maximum advantage of the ever-expanding World Wide Web. The text’s encyclopedic details, along with an array of additional resources for both students and teachers, are readily available via its dedicated web site (www.wiley.com/ constructioneducation). A test bank, PowerPoint slide show, review questions, Instructor’s Manual, and more can be found there. Coauthor Joseph Iano’s personal web site (www.ianosbackfill.com) provides an outlet for additional content and up-to-date coverage of new developments in the field. The selected list of web site addresses included in the reference section at the end of each chapter provides links to the other most relevant resources available on the Web, providing starting points for students’ further explorations. With this edition we have thoroughly updated references to contemporary building standards, codes, and practices, to ensure that the text remains the most current and accurate source of information on construction fundamentals available. Every chapter has been revised to reflect the latest versions of MasterFormat, the International Building Code, LEED, ANSI, and ASTM standards. Industry-specific standards, such as those from the American Concrete Institute (ACI), American Institute of Steel Construction (AISC), and American Architectural Manufacturers Association JWBK274_FM.indd xii (AAMA), to name just a few, have been thoroughly updated in the appropriate sections of the text as well. The updated and expanded companion Exercises in Building Construction and its answer key continue to provide a unique and invaluable tool for helping students to understand the real-world application of building construction knowledge to the design and construction of buildings. Despite the extensive scope of this latest revision, every change has been carefully reviewed by the authors and an independent board to be sure that the text remains up-to-date, accurate, and consistent with its original principles. In this way, as the book continues to change over time, the essential qualities that make it an educational success are preserved and strengthened. The authors’ special thanks go to the talented Lon R. Grohs, producer of the text’s stunning photorealistic illustrations, and in this latest edition, of the cover art as well. We are also grateful to the many photographers and organizations who have furnished new information and illustrations. The people of John Wiley & Sons, Inc. continue, as always, to demonstrate great professionalism. Amanda L. Miller, Vice President and Publisher, has for many years been a source of wisdom and support. Paul Drougas, Editor, has been invaluable for his industry knowledge, patience, and sense of humor. He is a true friend. Lauren Olesky, Assistant Developmental Editor, was reliable and helpful through all stages of this revision. Donna Conte, Senior Production Editor, continues, as in previous revisions, to oversee the most difficult task of managing production and schedules with grace and perseverance. We especially offer our thanks to the many teachers, students, and professionals who have purchased and used this work. Your satisfaction is our greatest reward, your loyalty is greatly appreciated, and your comments are always welcome! Joseph Iano dedicates this Fifth Edition to Lesley, Allen, Paul, and Ethan. E.A., South Natick, Massachusetts J.I., Seattle, Washington 10/30/08 5:42:03 AM Fundamentals of Building Construction JWBK274_FM.indd xiii 10/30/08 5:42:03 AM JWBK274_Ch01.indd Sec1:2 10/30/08 5:54:01 AM 1 Making Buildings • Learning to Build • Sustainability The Building Life Cycle Assessing Green Buildings • The Work of the Design Professional: Choosing Building Systems Zoning Ordinances Building Codes Other Constraints • Construction Standards and Information Resources Standards-Setting Agencies Construction Trade and Professional Associations MasterFormat • The Work of the Construction Professional: Constructing Buildings Providing Construction Services Construction Scheduling Managing Construction • Trends in the Delivery of Design and Construction Services Improving Collaboration Among Team Members Improving Efficiency in Production Improving Information Management • Recurring Concerns An ironworker connects a steel wide-flange beam to a column. (Courtesy of Bethlehem Steel Company) 3 JWBK274_Ch01.indd Sec1:3 10/30/08 5:54:10 AM We build because most human activities cannot take place outdoors. We need shelter from sun, wind, rain, and snow. We need dry, level platforms for our activities. Often we need to stack these platforms to multiply available space. On these platforms, and within our shelter, we need air that is warmer or cooler, more or less humid, than outdoors. We need less light by day, and more by night, than is offered by the natural world. We need services that provide energy, communications, and water and dispose of wastes. So, we gather materials and assemble them into the constructions we call buildings in an attempt to satisfy these needs. Learning to Build 4 Throughout this book many alternative ways of building are described: different structural systems, different systems of enclosure, and different systems of interior finish. Each system has characteristics that distinguish it from the alternatives. Sometimes a system is distinguished chiefly by its visual qualities, as one might acknowledge in choosing one type of granite over another, one color of paint over another, or one tile pattern over another. However, visual distinctions can extend beyond surface qualities; a designer may prefer the massive appearance of a masonry bearing wall building to the slender look of an exposed steel frame on one project, yet would choose the steel for another building whose situation is different. Again, one may choose for purely functional reasons, as in selecting terrazzo flooring that is highly durable and resistant to water instead of more vulnerable carpet or wood in a restaurant kitchen. One could choose on purely technical grounds, as, for example, in electing to posttension a long concrete beam for greater stiffness rather than rely on conventional steel reinforcing. A designer is often forced into a particular choice by some of the legal constraints identified later in this chapter. A choice is often influenced by considerations of environmental sustainability. And frequently the selection is made on purely economic grounds. The economic criterion can mean any JWBK274_Ch01.indd Sec1:4 of several things: Sometimes one system is chosen over another because its first cost is less; sometimes the entire life-cycle costs of competing systems are compared by means of formulas that include first cost, maintenance cost, energy consumption cost, the useful lifetime and replacement cost of the system, and interest rates on invested money; and, finally, a system may be chosen because there is keen competition among local suppliers and/or installers that keeps the cost of that system at the lowest possible level. This is often a reason to specify a very standard type of roofing material, for example, that can be furnished and installed by any of a number of companies, instead of a newer system that is theoretically better from a functional standpoint but can only be furnished by a single company that has the special equipment and skills required to install it. One cannot gain all the knowledge needed to make such decisions from a textbook. It is incumbent upon the reader to go far beyond what can be presented here—to other books, to catalogs, to trade publications, to professional periodicals, and especially to the design office, the workshop, and the building site. There is no other way to gain much of the required information and experience than to get involved in the art and business of building. One must learn how materials feel in the hand; how they look in a building; how they are manufactured, worked, and put in place; how they perform in service; how they deteriorate with time. One must become familiar with the people and organizations that produce buildings—the architects, engineers, materials suppliers, contractors, subcontractors, workers, inspectors, managers, and building owners—and learn to understand their respective methods, problems, and points of view. In the meantime, this long and hopefully enjoyable process of education in the materials and methods of building construction can begin with the information presented in this textbook. Go into the field where you can see the machines and methods at work that make the modern buildings, or stay in construction direct and simple until you can work naturally into buildingdesign from the nature of construction. Frank Lloyd Wright, To the Young Man in Architecture, 1931 Sustainability In constructing and occupying buildings, we expend vast quantities of the earth’s resources and generate a significant portion of the earth’s environmental pollution: The U.S. Green Building Council reported in 2008 that buildings account for 30 to 40 percent of the world’s energy use and associated greenhouse gas emissions. Construction and operation of buildings in the United States accounted for more than one-third of this country’s total energy use and the consumption of more than twothirds of its electricity, 30 percent of its raw materials, a quarter of its harvested wood, and 12 percent of its fresh water. Building construction and operation is responsible for nearly 10/30/08 5:54:14 AM Sustainability half of this country’s total greenhouse gas emissions and close to a third of its solid waste stream. Buildings are also significant emitters of particulates and other air pollutants. In short, building construction and operation cause many forms of environmental degradation that place an increasing burden on the earth’s resources and jeopardize the future of the building industry and societal health and welfare. Sustainability may be defined as meeting the needs of the present generation without compromising the ability of future generations to meet their needs. By consuming irreplaceable fossil fuels and other nonrenewable resources, by building in sprawling urban patterns that cover extensive areas of prime agricultural land, by using destructive forestry practices that degrade natural ecosystems, by allowing topsoil to be eroded by wind and water, and by generating substances that pollute water, soil, and air, we have been building in a manner that will make it increasingly difficult for our children and grandchildren to meet their needs for communities, buildings, and healthy lives. On the other hand, if we reduce building energy usage and utilize sunlight and wind as energy sources for our buildings, we reduce depletion of fossil fuels. If we reuse existing buildings imaginatively and arrange our new buildings in compact patterns on land of marginal value, we minimize the waste of valuable, productive land. If we harvest wood from forests that are managed in such a way that they can supply wood at a sustained level for the foreseeable future, we maintain wood construction as a viable option for centuries to come and protect the ecosystems that these forests support. If we protect soil and water through sound design and construction practices, we retain these resources for our successors. If we systematically reduce the various forms of pollution emitted in the processes of constructing and operating buildings, we keep the future environment cleaner. And as the industry becomes JWBK274_Ch01.indd Sec1:5 more experienced and committed to designing and building sustainably, it becomes increasingly possible to do these things with little or no increase in construction cost while creating buildings that are less expensive to operate and more healthful for their occupants for decades to come. Realization of these goals is dependent on our awareness of the environmental problems created by building activities, knowledge of how to overcome these problems, and skill in designing and constructing buildings that harness this knowledge. While the practice of sustainable design and construction, also called green building, remains a relatively recent development in the design and construction industry, its acceptance and support continue to broaden among public agencies, private developers, building operators and users, architectural and engineering firms, contractors, and materials producers. With each passing year, green building techniques are becoming less a design specialty and more a part of mainstream practice. The Building Life Cycle Sustainability must be addressed on a life-cycle basis, from the origins of the materials for a building, through the manufacture and installation of these materials and their useful lifetime in the building, to their eventual disposal when the building’s life is ended. Each step in this so-called cradle-to-grave cycle raises questions of sustainability. Origin and Manufacture of Materials for a Building Are the raw materials for a building plentiful or rare? Are they renewable or nonrenewable? How much of the content of a material is recycled from other uses? How much embodied energy is expended in obtaining and manufacturing the material, and how much water? What pollutants are discharged into air, water, and soil as a result of these acts? What wastes are / 5 created? Can these wastes be converted to useful products? Construction of the Building How much energy is expended in transporting a material from its origins to the building site, and what pollutants are generated? How much energy and water are consumed on the building site to put the material in place? What pollutants are associated with the installation of this material in the building? What wastes are generated, and how much of them can be recycled? Use and Maintenance of the Building How much energy and water does the building use over its lifetime as a consequence of the materials used in its construction and finishes? What problems of indoor air quality are caused by these materials? How much maintenance do these materials require, and how long will they last? Can they be recycled? How much energy and time are consumed in maintaining these materials? Does this maintenance involve use of toxic chemicals? Demolition of the Building What planning and design strategies can be used to extend the useful life of buildings, thereby forestalling resourceintensive demolition and construction of new buildings? When demolition is inevitable, how will the building be demolished and disposed of, and will any part of this process cause pollution of air, water, or soil? Can demolished materials be recycled into new construction or diverted for other uses rather than disposed of as wastes? One model for sustainable design is nature itself. Nature works in cyclical processes that are self-sustaining and waste nothing. More and more building professionals are learning to create buildings that work more nearly as nature does, helping to leave to our descendants a stock of healthful buildings, a sustainable supply of natural resources, and a clean environment that will enable them to live comfortably and responsibly and to 10/30/08 5:54:14 AM 6 / Chapter 1 • Making Buildings Figure 1.1 The LEED-NC 2009 Project Scorecard. The document shown here was in draft status at the time of this publication. See the U.S. Green Building Council web site for the most current version of this document. (Courtesy of U.S. Green Building Council) LEED for New Construction and Major Renovation 2009 Project Scorecard Project Name: Project Address: Yes ? No Sustainable Sites Y Prereq 1 Credit 1 Credit 2 Credit 3 Credit 4.1 Credit 4.2 Credit 4.3 Credit 4.4 Credit 5.1 Credit 5 5.2 2 Credit 6.1 Credit 6.2 Credit 7.1 Credit 7.2 Credit 8 Yes ? 26 Construction Activity Pollution Prevention Site Selection Development Density & Community Connectivity Brownfield Redevelopment Alternative Transportation, Public Transportation Access Alternative Transportation, Bicycle Storage & Changing Rooms Alternative Transportation, Low-Emitting & Fuel-Efficient Vehicles Alternative Transportation, Parking Capacity Site Development, Protect or Restore Habitat Site Development Development, Maximize Open Space Stormwater Design, Quantity Control Stormwater Design, Quality Control Heat Island Effect, Non-Roof Heat Island Effect, Roof Light Pollution Reduction Water Use Reduction, 20% Reduction Water Efficient Landscaping, Reduce by 50% Water Efficient Landscaping, No Potable Use or No Irrigation Credit 2 Innovative Wastewater Technologies Credit 3.1 Water Use Reduction, 30% Reduction Credit 3.2 Water Use Reduction, 40% Reduction Prereq 1 Required Credit 1.1 2 2 2 2 2 Energ y & Atmosphere gy Prereq 1 Prereq 2 Prereq 3 Credit 1 Credit 2 Credit 3 Credit 4 Credit 5 Credit 6 pass these riches on to their descendants in a never-ending succession. Assessing Green Buildings In the United States, the most widely adopted method for rating the environmental sustainability of a building’s design and construction is the U.S. Green Building Council’s Leadership in Energy and Environmental Design, or LEED™, rating system. LEED for New Construction and Major Renovation projects, termed LEED-NC, groups sustainability goals JWBK274_Ch01.indd Sec1:6 ? Points No Y Y Y Yes 1 5 1 6 1 3 2 1 1 1 1 1 1 1 10 Credit 1.2 ? Required No Water Efficiency Yes Points 35 Fundamental Commissioning of the Building Energy Systems Minimum Energy Performance: 10% New Bldgs or 5% Existing Bldg Renovations Fundamental Refrigerant Management Optimize Energy Performance 12% New Buildings or 8% Existing Building Renovations 16% New Buildings or 12% Existing Building Renovations 20% New Buildings or 16% Existing Building Renovations 24% New Buildings or 20% Existing Building Renovations 28% New Buildings or 24% Existing Building Renovations 32% New Buildings or 28% Existing Building Renovations 36% New Buildings or 32% Existing Building Renovations 40% New Buildings or 36% Existing Building Renovations 44% New Buildings or 40% Existing Building Renovations 48% New Buildings or 44% Existing Building Renovations On-Site Renewable Energy 1% Renewable Energy 5% Renewable Energy 9% Renewable Energy 13% Renewable Energy Enhanced Commissioning Enhanced Refrigerant Management Measurement & Verification Green Power Points Required Required Required 1 to 19 1 3 5 7 9 11 13 15 17 19 1 to 7 1 3 5 7 2 2 3 2 No into categories including site selection and development, efficiency in water use, reductions in energy consumption and in the production of atmospheric ozone-depleting gases, minimizing construction waste and the depletion of nonrenewable resources, improving the quality of the indoor environment, and encouraging innovation in sustainable design and construction practices (Figure 1.1). Within each category are specific credits that contribute points toward a building’s overall assessment of sustainability. Depending on the total number of points accumulated, four levels of sustainable design are recognized, including, in order of increasing performance, Certified, Silver, Gold, and Platinum. The process of achieving LEED certification for a proposed new building begins at the earliest stages of project conception, continues throughout the design and construction of the project, and involves the combined efforts of the owner, designer, and builder. During this process, the successful achievement of individual credits is documented and submitted to the 10/30/08 5:54:14 AM Sustainability Materials & Resources Y Prereq 1 Credit 1.1 C dit 1 Credit 1.2 2 Credit 1.3 Credit 2.1 Credit 2.2 Credit 3.1 Credit 3.2 Credit 4.1 Credit 4.2 Credit 5.1 Credit 5.2 Credit 6 Credit 7 Yes ? 14 Storage & Collection of Recyclables Building Reuse, Maintain 75% of Existing Walls, Floors & Roof B ildi R Building Reuse, Maintain M i t i 95% off E Existing i ti W Walls, ll Fl Floors & R Rooff Building Reuse, Maintain 50% of Interior Non-Structural Elements Construction Waste Management, Divert 50% from Disposal Construction Waste Management, Divert 75% from Disposal Materials Reuse, 5% Materials Reuse, 10% Recycled Content, 10% (post-consumer + ½ pre-consumer) Recycled Content, 20% (post-consumer + ½ pre-consumer) Regional Materials, 10% Extracted, Processed & Manufactured Regionally Regional Materials, 20% Extracted, Processed & Manufactured Regionally Rapidly Renewable Materials Certified Wood Y Y Prereq 1 Prereq 2 Credit 1 Credit 2 Credit 3.1 Credit 3.2 Credit 4.1 Credit 4.2 Credit 4.3 Credit 4.4 Credit 5 Credit 6.1 Credit 6.2 Credit 7.1 Credit 7.2 Credit 8.1 Credit 8.2 ? 15 Minimum IAQ Performance Environmental Tobacco Smoke (ETS) Control Outdoor Air Delivery Monitoring Increased Ventilation Construction IAQ Management Plan, During Construction Construction IAQ Management Plan, Before Occupancy Low-Emitting Materials, Adhesives & Sealants Low-Emitting Materials, Paints & Coatings Low-Emitting Materials, Flooring Systems Low-Emitting Materials, Composite Wood & Agrifiber Products Indoor Chemical & Pollutant Source Control Controllability of Systems, Lighting Controllability of Systems, Thermal Comfort Thermal Comfort, Design Thermal Comfort, Verification Daylight & Views, Daylight 75% of Spaces Daylight & Views, Views for 90% of Spaces Innovation & Design Process Credit 1.2 Credit 1.3 Credit 1.4 Credit 1.5 Credit 2 Points Required Required 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 ? 6 Innovation in Design: Provide Specific Title Innovation in Design: Provide Specific Title Innovation in Design: Provide Specific Title Innovation in Design: Provide Specific Title Innovation in Design: Provide Specific Title LEED® Accredited Professional Credit 1.1 Credit 1.2 Credit 1.3 Credit 1.4 ? Not Certified 1 1 1 1 1 1 4 Region Specific Environmental Priority: Region Defined Region Specific Environmental Priority: Region Defined Region Specific Environmental Priority: Region Defined Region Specific Environmental Priority: Region Defined Points 1 1 1 1 No Project Totals (Certification Estimates) 110 Points Certified: 40-49 points Silver: 50-59 points Gold: 60-79 points Platinum: 80+ points Green Building Council, which then makes the final certification of the project’s LEED compliance. The U.S. Green Building Council continues to refine and improve upon LEED-NC and is expanding its family of rating systems to include existing buildings (LEED-EB), commercial interiors (LEED-CI), building core and shell construction (LEED-CS), homes (LEED-H), and other categories of construction and development. Through international sister organizations, LEED is being implemented in Canada and other countries. Other green building JWBK274_Ch01.indd Sec1:7 Points No Regional Bonus Credits Yes 2 1 1 1 1 1 1 1 1 1 1 1 1 No Credit 1.1 Yes Required No Indoor Environmental Quality Yes Points programs, such as the Green Building Initiative’s Green Globes, the National Association of Home Builders’ Green Home Building Guidelines, and the International Code Council and National Association of Home Builders’ jointly developed National Green Building Standard, offer alternative assessment schemes. Some green building efforts focus more narrowly on reducing building energy consumption, a measure of building performance that frequently correlates closely with the generation of greenhouse gas emissions and global warming / 7 trends. The American Society of Heating, Refrigerating and Air-Conditioning Engineers’ Advanced Energy Design Guides and the U.S. Environmental Protection Agency’s Energy Star program both set goals for reductions in energy consumption in new buildings that exceed current national standards. These standards can be applied either as stand-alone programs or as part of a more comprehensive effort to achieve certification through LEED or some other green building assessment program. Buildings can also be designed with the goal of zero energy use or carbon neutrality. A net zero energy building is one that consumes no more energy than it produces, usually when measured on an annual basis to account for seasonal differences in building energy consumption and on-site energy production. Net zero energy use can be achieved using current technology combining on-site renewable energy generation (such as wind or solar power), passive heating and cooling strategies, a thermally efficient building enclosure, and highly efficient mechanical systems and appliances. A carbon-neutral building is one that causes no net increase in the emission of carbon dioxide, the most prevalent atmospheric greenhouse gas. If emissions due only to building operation are considered, the calculation is similar to that for a net zero energy building. If, however, the embodied carbon in the building’s full life cycle—from materials extraction and manufacturing, through building construction and operations, to demolition, disposal, and recycling—is considered, the calculation becomes more complex. Carbon-neutral calculations may also consider the site on which the building resides. For example, what is the carbon footprint of a fully developed building site, including both its buildings and unbuilt areas, in comparison to that of the site prior to construction or in comparison to its natural state prior to human development of any kind? Another possible 10/30/08 5:54:15 AM 8 / Chapter 1 • Making Buildings consideration is, what role, if any, should carbon offsetting (funding of offsite activities that reduce global carbon emissions, such as planting of trees), play in such calculations? Questions such as these and the concepts of sustainability and how they relate to building construction will continue to evolve for the foreseeable future. Considerations of sustainability are included throughout this book. In addition, a sidebar in nearly every chapter describes the major issues of sustainability related to the materials and methods discussed in that chapter. These will be helpful in weighing the environmental costs of one material against those of another, and in learning how to build in such a way that we preserve for future generations the ability to meet their building needs in a reasonable and economical manner. For more information on organizations whose mission is to raise our awareness and provide the knowledge that we need to build sustainably, see the references listed at the end of this chapter. The Work of the Design Professional: Choosing Building Systems A building begins as an idea in someone’s mind, a desire for new and ample accommodations for a family, many families, an organization, or an enterprise. For any but the smallest buildings, the next step for the owner of the prospective building is to engage, either directly or through a hired construction manager, the services of building design professionals. An architect helps to organize the owner’s ideas about the new building, develops the form of the building, and assembles a group of engineering specialists to help work out concepts and details of foundations, structural support, and mechanical, electrical, and communications services. JWBK274_Ch01.indd Sec1:8 . . . the architect should have construction at least as much at his fingers’ ends as a thinker his grammar. Le Corbusier, Towards a New Architecture, 1927 This team of designers, working with the owner, then develops the scheme for the building in progressively finer degrees of detail. Drawings and written specifications are produced by the architect–engineer team to document how the building is to be made and of what. The drawings and specifications are submitted to the local government building authorities, where they are checked for conformance with zoning ordinances and building codes before a permit is issued to build. A general contractor is selected, either by negotiation or by competitive bidding, who then hires subcontractors to carry out many specialized portions of the work. Once construction begins, the general contractor oversees the construction process while the building inspector, architect, and engineering consultants observe the work at frequent intervals to be sure that it is carried out according to plan. Finally, construction is finished, the building is made ready for occupancy, and that original idea, often initiated years earlier, is realized. Although a building begins as an abstraction, it is built in a world of material realities. The designers of a building—the architects and engineers—work constantly from a knowledge of what is possible and what is not. They are able, on the one hand, to employ a seemingly limitless palette of building materials and any of a number of structural systems to produce a building of almost any desired form and texture. On the other hand, they are inescapably bound by certain physical limitations: how much land there is with which to work; how heavy a building the soil can support; how long a structural span is feasible; what sorts of materials will perform well in the given environment. They are also constrained by a construction budget and by a complex web of legal restrictions. Those who work in the building professions need a broad understanding of many things, including people and culture, the environment, the physical principles by which buildings work, the technologies available for utilization in buildings, the legal restrictions on building design and use, the economics of building, and the contractual and practical arrangements under which buildings are constructed. This book is concerned primarily with the technologies of construction—what the materials are, how they are produced, what their properties are, and how they are crafted into buildings. These must be studied, however, with reference to many other factors that bear on the design of buildings, some of which require explanation here. Zoning Ordinances The legal restrictions on buildings begin with local zoning ordinances, which govern the types of activities that may take place on a given piece of land, how much of the land may be covered by buildings, how far buildings must be set back from adjacent property lines, how many parking spaces must be provided, how large a total floor area may be constructed, and how tall the buildings may be. In larger cities, zoning ordinances may include fire zones with special fire-protection requirements, neighborhood enterprise districts with economic incentives for new construction or revitalization of existing buildings, or other special conditions. Building Codes In addition to its zoning ordinances, local governments regulate building activity by means of building codes. Building codes protect public health and safety by setting minimum standards for construction quality, 10/30/08 5:54:15 AM The Work of the Design Professional: Choosing Building Systems structural integrity, durability, livability, accessibility, and especially fire safety. Most building codes in North America are based on one of several model building codes, standardized codes that local jurisdictions may adopt for their own use as an alternative to writing their own. In Canada, the National Building Code of Canada is published by the Canadian Commission on Building and Fire Codes. It is the basis for most of that country’s provincial and municipal building codes. In the United States, the International Building Code® is the predominant model code. This code is published by the International Code Council, a private, nonprofit organization whose membership consists of local code officials from throughout the country. It is the basis for most U.S. building codes enacted at the state, county, and municipal levels. The International Building Code (IBC) is the first unified model building code in U.S. history. First published in March 2000, it was a welcome consolidation of a number of previous competing regional model codes. Building-code-related information in this book is based on the IBC. The IBC begins by defining occupancy groups for buildings as follows: • Groups A-1 through A-5 are public Assembly occupancies: theaters, auditoriums, lecture halls, nightclubs, restaurants, houses of worship, libraries, museums, sports arenas, and so on. • Group B is Business occupancies: banks, administrative offices, higher-education facilities, post offices, banks, professional offices, and the like. • Group E is Educational occupancies: schools for grades K through 12 and day-care facilities. • Groups F-1 and F-2 comprise industrial processes using moderateflammability or noncombustible materials, respectively. • Groups H-1 through H-5 include various types of High Hazard occupancies in which toxic, corrosive, JWBK274_Ch01.indd Sec1:9 highly flammable, or explosive materials are present. • Groups I-1 through I-4 are Institutional occupancies in which occupants under the care of others may not be able to save themselves during a fire or other building emergency, such as health care facilities, custodial care facilities, and prisons. • Group M is Mercantile occupancies: stores, markets, service stations, and salesrooms. • Groups R-1 through R-4 are Residential occupancies, including apartment buildings, dormitories, fraternity and sorority houses, hotels, one- and two-family dwellings, and assistedliving facilities. • Groups S-1 and S-2 include buildings for Storage of moderate- and low-hazard materials, respectively. • Group U is Utility buildings. It comprises agricultural buildings, carports, greenhouses, sheds, stables, fences, tanks, towers, and other secondary buildings. The IBC’s purpose in establishing occupancy groups is to distinguish various degrees of need for safety in buildings. A hospital, in which many patients are bedridden and cannot escape a fire without assistance from others, must be built to a higher standard of safety than a hotel or motel. A warehouse storing noncombustible masonry materials, which is likely to be occupied by only a few people, all of them able-bodied, can be constructed to a lower standard than a large retail mall building, which will house large quantities of combustible materials and will be occupied by many users varying in age and physical capability. An elementary school requires more protection for its occupants than a university building. A theater needs special egress provisions to allow its many patrons to escape quickly, without stampeding, in an emergency. These definitions of occupancy groups are followed by a set of definitions of construction types. At the head / 9 of this list is Type I construction, made with highly fire-resistant, noncombustible materials. At the foot of it is Type V construction, which is built from combustible wood framing—the least fire-resistant of all construction types. In between are Types II, III, and IV, with levels of resistance to fire falling between these two extremes. With occupancy groups and construction types defined, the IBC proceeds to match the two, stating which occupancy groups may be housed in which types of construction, and under what limitations of building height and area. Figure 1.2 is reproduced from the IBC. This table gives values for the maximum building height, in both feet and number of stories above grade, and the maximum area per floor for every possible combination of occupancy group and construction type. Once these base values are adjusted according to other provisions of the code, the maximum permitted size for a building of any particular use and type of construction can be determined. This table concentrates a great deal of important information into a very small space. A designer may refer to it with a particular building type in mind and find out what types of construction will be permitted and what shape the building may take. Consider, for example, an office building. Under the IBC, a building of this type belongs to Occupancy Group B, Business. Reading across the table from left to right, we find immediately that this building may be built to any desired size, without limit, using Type I-A construction. Type I-A construction is defined in the IBC as consisting of only noncombustible materials—masonry, concrete, or steel, for example, but not wood—and meeting minimum requirements for resistance to the heat of fire. Looking at the upper table in Figure 1.3, also reproduced from the IBC, we find under Type I-A construction a listing of the required fire resistance ratings, measured in hours, for various parts of our proposed office 10/30/08 5:54:15 AM 10 / Chapter 1 • Making Buildings TABLE 503 ALLOWABLE HEIGHT AND BUILDING AREASa Height limitations shown as stories and feet above grade plane. Area limitations as determined by the definition of “Area, building,” per story TYPE OF CONSTRUCTION TYPE I TYPE II TYPE III TYPE IV TYPE V A B A B A B HT A B HGT(feet) GROUP HGT(S) UL 160 65 55 65 55 65 50 40 A-1 S A UL UL 5 UL 3 15,500 2 8,500 3 14,000 2 8,500 3 15,000 2 11,500 1 5,500 A-2 S A UL UL 11 UL 3 15,500 2 9,500 3 14,000 2 9,500 3 15,000 2 11,500 1 6,000 A-3 S A UL UL 11 UL 3 15,500 2 9,500 3 14,000 2 9,500 3 15,000 2 11,500 1 6,000 A-4 S A UL UL 11 UL 3 15,500 2 9,500 3 14,000 2 9,500 3 15,000 2 11,500 1 6,000 A-5 S A UL UL UL UL UL UL UL UL UL UL UL UL UL UL UL UL UL UL B S A UL UL 11 UL 5 37,500 4 23,000 5 28,500 4 19,000 5 36,000 3 18,000 2 9,000 E S A UL UL 5 UL 3 26,500 2 14,500 3 23,500 2 14,500 3 25,500 1 18,500 1 9,500 F-1 S A UL UL 11 UL 4 25,000 2 15,500 3 19,000 2 12,000 4 33,500 2 14,000 1 8,500 F-2 S A UL UL 11 UL 5 37,500 3 23,000 4 28,500 3 18,000 5 50,500 3 21,000 2 13,000 H-1 S A 1 21,000 1 16,500 1 11,000 1 7,000 1 9,500 1 7,000 1 10,500 1 7,500 NP NP H-2d S A UL 21,000 3 16,500 2 11,000 1 7,000 2 9,500 1 7,000 2 10,500 1 7,500 1 3,000 H-3d S A UL UL 6 60,000 4 26,500 2 14,000 4 17,500 2 13,000 4 25,500 2 10,000 1 5,000 H-4 S A UL UL 7 UL 5 37,500 3 17,500 5 28,500 3 17,500 5 36,000 3 18,000 2 6,500 H-5 S A 4 UL 4 UL 3 37,500 3 23,000 3 28,500 3 19,000 3 36,000 3 18,000 2 9,000 I-1 S A UL UL 9 55,000 4 19,000 3 10,000 4 16,500 3 10,000 4 18,000 3 10,500 2 4,500 I-2 S A UL UL 4 UL 2 15,000 1 11,000 1 12,000 NP NP 1 12,000 1 9,500 NP NP I-3 S A UL UL 4 UL 2 15,000 1 10,000 2 10,500 1 7,500 2 12,000 2 7,500 1 5,000 I-4 S A UL UL 5 60,500 3 26,500 2 13,000 3 23,500 2 13,000 3 25,500 1 18,500 1 9,000 M S A UL UL 11 UL 4 21,500 4 12,500 4 18,500 4 12,500 4 20,500 3 14,000 1 9,000 R-1 S A UL UL 11 UL 4 24,000 4 16,000 4 24,000 4 16,000 4 20,500 3 12,000 2 7,000 R-2 S A UL UL 11 UL 4 24,000 4 16,000 4 24,000 4 16,000 4 20,500 3 12,000 2 7,000 R-3 S A UL UL 11 UL 4 UL 4 UL 4 UL 4 UL 4 UL 3 UL 3 UL R-4 S A UL UL 11 UL 4 24,000 4 16,000 4 24,000 4 16,000 4 20,500 3 12,000 2 7,000 S-1 S A UL UL 11 48,000 4 26,000 3 17,500 3 26,000 3 17,500 4 25,500 3 14,000 1 9,000 S-2b, c S A UL UL 11 79,000 5 39,000 4 26,000 4 39,000 4 26,000 5 38,500 4 21,000 2 13,500 Uc S A UL UL 5 35,500 4 19,000 2 8,500 3 14,000 2 8,500 4 18,000 2 9,000 1 5,500 For SI: 1 foot = 304.8 mm, 1 square foot = 0.0929 m2. UL = Unlimited, NP = Not permitted. a. See the following sections for general exceptions to Table 503: 1. Section 504.2, Allowable height increase due to automatic sprinkler system installation. 2. Section 506.2, Allowable area increase due to street frontage. 3. Section 506.3, Allowable area increase due to automatic sprinkler system installation. 4. Section 507, Unlimited area buildings. b. For open parking structures, see Section 406.3. c. For private garages, see Section 406.1. d. See Section 415.5 for limitations. JWBK274_Ch01.indd Sec1:10 10/30/08 5:54:15 AM The Work of the Design Professional: Choosing Building Systems building. For example, the first line states that the structural frame, including such elements as columns, beams, and trusses, must be rated at 3 hours. The second line also mandates a 3-hour resistance for bearing walls, which serve to carry floors or Figure 1.2 Height and area limitations of buildings of various types of construction, as defined in the 2006 IBC. (Portions of this publication reproduce tables from the 2006 International Building Code, International Code Council, Inc., Washington, D.C. Reproduced with Permission. All rights reserved.) / 11 Figure 1.3 Fire resistance of building elements as required by the 2006 IBC. (Portions of this publication reproduce tables from the 2006 International Building Code, International Code Council, Inc., Washington, D.C. Reproduced with Permission. All rights reserved.) TABLE 601 FIRE-RESISTANCE RATING REQUIREMENTS FOR BUILDING ELEMENTS (hours) TYPE I Structural TYPE II e TYPE III e TYPE IV TYPE V e BUILDING ELEMENT A B A B A B HT A B framea 3b 2b 1 0 1 0 HT 1 0 3 3b 2 2b 1 1 0 0 2 1 2 0 2 1/HT 1 1 0 0 Bearing walls Exteriorg Interior Nonbearing walls and partitions Exterior See Table 602 Nonbearing walls and partitions Interiorf 0 0 0 0 0 0 See Section 602.4.6 0 0 Floor construction Including supporting beams and joists 2 2 1 0 1 0 HT 1 0 Roof construction Including supporting beams and joists 11/2c 1c, d 1c, d 0d 1d 0d HT 1c, d 0 For SI: 1 foot = 304.8 mm. a. The structural frame shall be considered to be the columns and the girders, beams, trusses and spandrels having direct connections to the columns and bracing members designed to carry gravity loads. The members of floor or roof panels which have no connection to the columns shall be considered secondary members and not a part of the structural frame. b. Roof supports: Fire-resistance ratings of structural frame and bearing walls are permitted to be reduced by 1 hour where supporting a roof only. c. Except in Group F-1, H, M and S-1 occupancies, fire protection of structural members shall not be required, including protection of roof framing and decking where every part of the roof construction is 20 feet or more above any floor immediately below. Fire-retardant-treated wood members shall be allowed to be used for such unprotected members. d. In all occupancies, heavy timber shall be allowed where a 1-hour or less fire-resistance rating is required. e. An approved automatic sprinkler system in accordance with Section 903.3.1.1 shall be allowed to be substituted for 1-hour fire-resistance-rated construction, provided such system is not otherwise required by other provisions of the code or used for an allowable area increase in accordance with Section 506.3 or an allowable height increase in accordance with Section 504.2. The 1-hour substitution for the fire resistance of exterior walls shall not be permitted. f. Not less than the fire-resistance rating required by other sections of this code. g. Not less than the fire-resistance rating based on fire separation distance (see Table 602). TABLE 602 FIRE-RESISTANCE RATING REQUIREMENTS FOR EXTERIOR WALLS BASED ON FIRE SEPARATION DISTANCEa, e FIRE SEPARATION DISTANCE = X (feet) TYPE OF CONSTRUCTION OCCUPANCY GROUP H OCCUPANCY GROUP F-1, M, S-1 OCCUPANCY GROUP A, B, E, F-2, I, R, S-2, Ub All 3 2 1 5 ≤ X <10 IA Others 3 2 2 1 1 1 10 ≤ X< 30 IA, IB IIB, VB Others 2 1 1 1 0 1 1d 0 1d X ≥ 30 All 0 0 0 X< c For SI: 1 foot = 304.8 mm. a. Load-bearing exterior walls shall also comply with the fire-resistance rating requirements of Table 601. b. For special requirements for Group U occupancies see Section 406.1.2 c. See Section 705.1.1 for party walls. d. Open parking garages complying with Section 406 shall not be required to have a fire-resistance rating. e. The fire-resistance rating of an exterior wall is determined based upon the fire separation distance of the exterior wall and the story in which the wall is located. JWBK274_Ch01.indd Sec1:11 10/30/08 5:54:16 AM 12 / Chapter 1 • Making Buildings roofs above. Nonbearing walls or partitions, which carry no load from above, are listed in the third line, referring to Table 602, which gives fire resistance rating requirements for exterior walls of a building based on their proximity to adjacent buildings. (Table 602 is included in the lower portion of Figure 1.3.) Requirements for floor and roof construction are defined in the last two lines of Table 601. Looking across Table 601 in Figure 1.3, we can see that fire resistance rating requirements are highest for Type I-A construction, decrease to 1 hour for various intermediate types, and fall to zero for Type V-B construction. In general, the lower the construction type numeral, the more fire-resistant the construction system is. (Type IV construction is somewhat of an anomaly, referring to Heavy Timber construction consisting of large wooden members that are relatively slow to catch fire and burn.) Once fire resistance rating requirements for the major parts of a building have been determined the design of these parts can proceed, using building assemblies meeting these requirements. Tabulated fire resistance ratings for common building materials and assemblies may come from a variety of sources, including the IBC itself, as well as a from catalogs and handbooks issued by building material manufacturers, construction trade associations, and organizations concerned with fire protection of buildings. In each case, the ratings are derived from full-scale laboratory tests of building components carried out in accordance with an accepted standard fire test protocol to ensure uniformity of results. (This test, ASTM E119, is described more fully in Chapter 22 of this book.) Figures 1.4 to 1.6 show sections of tables from catalogs and handbooks to illustrate how such fire resistance ratings are commonly presented. In general, when determining the level of fire resistance required for a building, the greater the degree of fire resistance, the higher JWBK274_Ch01.indd Sec1:12 Figure 1.4 Examples of fire resistance ratings for concrete and masonry structural elements. The upper detail, taken from the Underwriters Laboratories Fire Resistance Directory, is for a precast concrete hollow-core plank floor with a poured concrete topping. Restrained and unrestrained refer to whether or not the floor is prevented from expanding longitudinally when exposed to the heat of a fire. The lower detail is from literature published by the Brick Institute of America. (Reprinted with permission of Underwriters Laboratories Inc. and the Brick Institute of America, respectively.) 10/30/08 5:54:16 AM The Work of the Design Professional: Choosing Building Systems / 13 Figure 1.5 Fire resistance ratings for a steel floor structure and column, respectively, taken from the Underwriters Laboratories Fire Resistance Directory. (Reprinted with permission of Underwriters Laboratories Inc.) Figure 1.6 A sample of fire resistance ratings published by the Gypsum Association, in this case for an interior partition. (Courtesy of the Gypsum Association) JWBK274_Ch01.indd Sec1:13 10/30/08 5:54:16 AM 14 / Chapter 1 • Making Buildings the cost. Most frequently, therefore, buildings are designed with the lowest level of fire resistance permitted by the building code. Our hypothetical office building could be built using Type IA construction, but does it really need to be constructed to this high standard? Let us suppose that the owner desires a five-story building with 30,000 square feet per floor. Reading across the table in Figure 1.2, we can see that in addition to Type I-A construction, the building can be of Type I-B construction, which permits a building of eleven stories and unlimited floor area, or of Type II-A construction, which permits a building of five stories and 37,500 square feet per floor. But it cannot be of Type II-B construction, which allows a building of only four stories and 23,000 square feet per floor. It can also be built of Type IV construction but not of Type III or Type V. Other factors also come into play in these determinations. If a building is protected throughout by an approved, fully automatic sprinkler system for suppression of fire, the IBC provides that the tabulated area per floor may be quadrupled for a singlestory building or as much as tripled for a multistory building (depending on additional considerations omitted here for the sake of simplicity). A one-story increase in allowable height is also granted under most circumstances if such a sprinkler system is installed. If the five-story, 30,000square-foot office building that we have been considering is provided with such a sprinkler system, a bit of arithmetic will show that it can be built of any construction type shown in Figure 1.2 except Type V. If more than a quarter of the building’s perimeter walls face public ways or open spaces accessible to firefighting equipment, an additional increase of up to 75 percent in allowable area is granted in accordance with another formula. Furthermore, if a building is divided by fire walls having the fire resistance JWBK274_Ch01.indd Sec1:14 TABLE 705.4 FIRE WALL FIRE-RESISTANCE RATINGS GROUP FIRE-RESISTANCE RATING (hours) A, B, E, H-4, I, R-1, R-2, U 3a F-1, H-3b, H-5, M, S-1 3 H-1, H-2 4b F-2, S-2, R-3, R-4 2 a. Walls shall be not less than 2-hour fire-resistance rated where separating buildings of Type II or V construction. b. For Group H-1, H-2 or H-3 buildings, also see Sections 415.4 and 415.5. Figure 1.7 Fire resistance requirements for fire walls, according to the 2006 IBC. (Portions of this publication reproduce tables from the 2006 International Building Code, International Code Council, Inc., Washington, D.C. Reproduced with Permission. All rights reserved.) ratings specified in another table (Figure 1.7), each divided portion may be considered a separate building for purposes of computing its allowable area, which effectively permits the creation of a building many times larger than Figure 1.2 would, at first glance, indicate. The IBC also establishes standards for natural light, ventilation, means of emergency egress, structural design, construction of floors, walls, and ceilings, chimney construction, fire protection systems, accessibility for disabled persons, and many other important factors. The International Code Council also publishes the International Residential Code (IRC), a simplified model code specifically addressing the construction of detached one- and two-family homes and townhouses of limited size. Within any particular building agency, buildings of these types may fall under the requirements of either the IBC or the IRC, depending on the code adoption policies of that jurisdiction. The building code is not the only code with which a new building must comply. Health codes regulate aspects of design and operation related to sanitation in public facilities such as swimming pools, food-service operations, schools, or health care facilities. Energy codes establish standards of energy efficiency for buildings affecting a designer’s choices of windows, heating and cooling systems, and many aspects of the construction of a building’s enclosing walls and roofs. Fire codes regulate the operation and maintenance of buildings to ensure that egress pathways, fire protection systems, emergency power, and other life-safety systems are properly maintained. Electrical and mechanical codes regulate the design and installation of building electrical, plumbing, and heating and cooling systems. Some of these codes may be locally written. But like the building codes discussed above, most are based on national models. In fact, an important task in the early design of any major building is determining what agencies have jurisdiction over the project and what codes and regulations apply. Other Constraints Other types of legal restrictions must also be observed in the design and construction of buildings. The Americans with Disabilities Act (ADA) makes accessibility to public buildings a civil right of all Americans, and the Fair Housing Act does the same for much multifamily housing. These access 10/30/08 5:54:17 AM Construction Standards and Information Resources standards regulate the design of entrances, stairs, doorways, elevators, toilet facilities, public areas, living spaces, and other parts of affected buildings to ensure that they are accessible and usable by physically handicapped members of the population. The U.S. Occupational Safety and Health Administration (OSHA) controls the design of workplaces to minimize hazards to the health and safety of workers. OSHA sets safety standards under which a building must be constructed and also has an important effect on the design of industrial and commercial buildings. An increasing number of states have limitations on the amount of volatile organic compounds (VOCs) that building products can release into the atmosphere. VOCs are organic chemical compounds that evaporate readily. They can act as irritants to building occupants, they contribute to air pollution, and some are greenhouse gases. Typical sources of VOCs are paints, stains, adhesives, and binders used in the manufacture of wood panel products. States and localities have conservation laws that protect wetlands and other environmentally sensitive areas from encroachment by buildings. Fire insurance companies exert a major influence on construction standards through their testing and certification organizations (Underwriters Laboratories and Factory Mutual, for example) and through their rate structures for building insurance coverage, which offer strong financial incentives to building owners for more hazard-resistant construction. Building contractors and construction labor unions have standards, both formal and informal, that affect the ways in which buildings are built. Unions have work rules and safety rules that must be observed; contractors have particular types of equipment, certain kinds of skills, and customary ways of going about things. All of these vary significantly from one place to another. JWBK274_Ch01.indd Sec1:15 Construction Standards and Information Resources The tasks of the architect and the engineer would be impossible to carry out without the support of dozens of standards-setting agencies, trade associations, professional organizations, and other groups that produce and disseminate information on materials and methods of construction, some of the most important of which are discussed in the sections that follow. Standards-Setting Agencies ASTM International (formerly the American Society for Testing and Materials) is a private organization that establishes specifications for materials and methods of construction accepted as standards throughout the United States. Numerical references to ASTM standards—for example, ASTM C150 for portland cement, used in making concrete—are found throughout building codes and construction specifications, where they are used as a precise shorthand for describing the quality of materials or the requirements of their installation. Throughout this book, references to ASTM standards are provided for the major building materials presented. Should you wish to examine the contents of the standards themselves, they can be found in the ASTM references listed at the end of this chapter. In Canada, corresponding standards are set by the Canadian Standards Association (CSA). The American National Standards Institute (ANSI) is another private organization that develops and certifies North American standards for a broad range of products, such as exterior windows, mechanical components of buildings, and even the accessibility requirements referenced within the IBC itself (ICC/ANSI A117.1). Government agencies, most notably the U.S. Department of Commerce’s / 15 National Institute of Science and Technology (NIST) and the National Research Council Canada’s Institute for Research in Construction (NRC-IRC), also sponsor research and establish standards for building products and systems. Construction Trade and Professional Associations Design professionals, building materials manufacturers, and construction trade groups have formed a large number of organizations that work to develop technical standards and disseminate information related to their respective fields of interest. The Construction Specifications Institute, whose MasterFormat™ standard is described in the following section, is one example. This organization is composed both of independent building professionals, such as architects and engineers, and of industry members. The Western Wood Products Association, to choose an example from among hundreds of trade associations, is made up of producers of lumber and wood products. It carries out research programs on wood products, establishes uniform standards of product quality, certifies mills and products that conform to its standards, and publishes authoritative technical literature concerning the use of lumber and related products. Associations with a similar range of activities exist for virtually every material and product used in building. All of them publish technical data relating to their fields of interest, and many of these publications are indispensable references for the architect or engineer. A considerable number of the standards published by these organizations are incorporated by reference into the building codes. Selected publications from professional and trade associations are identified in the references listed at the end of each chapter in this book. The reader is encouraged to obtain and explore these publications and others available from these various organizations. 10/30/08 5:54:17 AM 16 / Chapter 1 • Making Buildings MasterFormat The Construction Specifications Institute (CSI) of the United States and its Canadian counterpart, Construction Specifications Canada (CSC), have evolved over a period of many years a comprehensive outline called MasterFormat for organizing information about construction materials and systems. MasterFormat is used as the outline for construction specifications for the vast majority of large construction projects in these two countries, it is frequently used to organize construction cost data, and it forms the basis on which most trade associations’ and manufacturers’ technical literature is cataloged. In some cases, MasterFormat is used to cross-reference materials information on construction drawings as well. MasterFormat is organized into 50 primary divisions intended to cover the broadest possible range of construction materials and buildings systems. The portions of MasterFormat relevant to the types of construction discussed in this book are as follows: Procurement and Contracting Requirements Group Division 0 0 — Procurement and Contracting Requirements Specifications Group General Requirements Subgroup Division 0 1 — General Requirements Facility Construction Subgroup Division 0 2 — Existing Conditions Division 0 3 — Concrete Division 0 4 — Masonry Division 0 5 — Metals Division 0 6 — Wood, Plastics, and Composites Division 0 7 — Thermal and Moisture Protection Division 0 8 — Openings Division 0 9 — Finishes Division 1 0 — Specialties JWBK274_Ch01.indd Sec1:16 Division 1 1 — Equipment Division 1 2 — Furnishings Division 1 3 — Special Construction Division 1 4 — Conveying Equipment Facilities Services Subgroup Division 2 1 — Fire Suppression Division 2 2 — Plumbing Division 2 3 — Heating, Ventilating, and Air Conditioning Division 2 5 — Integrated Automation Division 2 6 — Electrical Division 2 7 — Communications Division 2 8 — Electronic Safety and Security Site and Infrastructure Subgroup Division 3 1 — Earthwork Division 3 2 — Exterior Improvements Division 3 3 — Utilities These broadly defined divisions are further subdivided into sections, each describing a discrete scope of work usually provided by a single construction trade or subcontractor. Individual sections are identified by sixdigit codes, in which the first two digits correspond to the division numbers above and the remaining four digits identify subcategories and individual units within the division. Within Division 05 – Metals, for example, some commonly referenced sections are: Section 05 10 00 — Structural Steel Framing Section 05 21 00 — Steel Joist Framing Section 05 31 00 — Steel Decking Section 05 40 00 — Cold-Formed Metal Framing Section 05 50 00 — Metal Fabrications Almost every chapter in this book gives MasterFormat designations for the information it presents to help the reader know where to look in construction specifications and other technical resources for further information. The full MasterFormat system is contained in the volume referenced at the end of this chapter. MasterFormat organizes building systems information primarily according to work product, that is, the work of discrete building trades, making it especially well suited for use during the construction phase of building. Other organizational systems, such as Uniformat™ and OmmiClass™, offer a range of alternative organizational schemes suitable to other phases of the building life cycle and other aspects of building functionality. See the references at the end of this chapter for more information about these systems. The Work of the Construction Professional: Constructing Buildings Providing Construction Services An owner wishing to construct a building hopes to achieve a finished project that meets its functional requirements and its expectations for design and quality, at the lowest possible cost, and on a predictable schedule. A contractor offering its construction services hopes to produce quality work, earn a profit, and complete the project in a timely fashion. Yet, the process of building itself is fraught with uncertainty: It is subject to the vagaries of the labor market, commodity prices, and the weather; despite the best planning efforts unanticipated conditions arise, delays occur, and mistakes are made; and the pressures of schedule and cost inevitably minimize the margin for miscalculation. In this high-stakes environment, the 10/30/08 5:54:17 AM The Work of the Construction Professional: Constructing Buildings / 17 Figure 1.8 In design/bid/build project delivery, the owner contracts separately with the architect/engineer (A/E) design team and the construction general contractor (GC). In a design/build project, the owner contracts with a single organizational entity that provides both design and construction services. relationship between the owner and contractor must be structured to share reasonably between them the potential rewards and risks. Construction Project Delivery Methods In conventional design/bid/build project delivery (Figure 1.8), the owner first hires a team of architects and engineers to perform design services, leading to the creation of drawings and technical specifications, referred to collectively as the construction documents, that comprehensively describe the facility to be built. Next, construction firms are invited to bid on the project. Each bidding firm reviews the construction documents and proposes a cost to construct the facility. The owner evaluates the submitted proposals and awards the construction contract to the bidder deemed most suitable. This selection may be based on bid price alone, or other factors related to bidders’ qualifications may also be considered. The construction documents then become part of the construction contract, and the selected firm proceeds with the work. On all but small projects, this firm acts as the general contractor, coordinating and overseeing the overall construction process but frequently relying on smaller, more specialized subcontractors to perform significant portions or even all of the construction work. During construction, the design team continues to provide services to the owner, helping to ensure that the facility is built according to the requirements of the documents as well as answering questions related JWBK274_Ch01.indd Sec1:17 to the design, changes to the work, payments to the contractor, and similar matters. Among the advantages of design/bid/build project delivery are its easy-to-understand organizational structure, well-established legal precedents, and ease of management. The direct relationship between the owner and the design team ensures that the owner retains control over the design and provides a healthy set of checks and balances during the construction process. Also, with design work completed before the project is bid, the owner starts construction with a fixed construction cost and a high degree of confidence regarding the final costs of the project. In design/bid/build project delivery, the owner contracts with two entities, and design and construction responsibilities remain divided between these two throughout the project. In design/build project delivery, one entity ultimately assumes responsibility for both design and construction (Figure 1.8). A design/ build project begins with the owner developing a conceptual design or program that describes the functional or performance requirements of the proposed facility but does not detail its form or how it is to be constructed. Next, using this conceptual information, a design/build organization is selected to complete all remaining aspects of the project. Selection of the designer/builder may be based on a competitive bid process similar to that described above for design/bid/build projects, on negotiation and evaluation of an organization’s qualifications for the proposed work, or on some combination of both. Design/ build organizations themselves can take a variety of forms: a single firm encompassing both design and construction expertise, a construction management firm that subcontracts with a separate design firm to provide those services, or a joint venture between two firms, one specializing in construction and the other in design. Regardless of the internal structure of the design/build organization, the owner contracts with this single entity throughout the remainder of the project, which assumes responsibility for all remaining design and construction services. Design/build project delivery gives the owner a single source of accountability for all aspects of the project. It also places the designers and constructors in a collaborative relationship, introducing construction expertise into the design phases of a project and allowing the earliest possible consideration of constructability, cost control, construction scheduling, and similar matters. This delivery method also readily accommodates fast track construction, a scheduling technique for reducing construction time that is described below. Other delivery methods are possible: An owner may contract separately with a design team and a construction manager. As in design/build construction, the construction manager participates in the project prior to the onset of construction, introducing construction expertise during the design stage. Construction management project delivery can take a variety of forms and is frequently associated with especially large or complex 10/30/08 5:54:17 AM 18 / Chapter 1 • Making Buildings Figure 1.9 In its traditional role, a construction manager (CM) at fee provides project management services to the owner and assists the owner in contracting directly for construction services with one or more construction entities. A CM at fee is not directly responsible for the construction work itself. A CM at risk acts more like a general contractor and takes on greater responsibility for construction quality, schedule, and costs. In either case, the A/E design team also contracts separately with the owner. projects (Figure 1.9). In turnkey construction, an owner contracts with a single entity that provides not only design and construction services, but financing for the project as well. Or design and construction can be undertaken by a single-purpose entity, of which the owner, architect, and contractor are all joint members. Aspects of these and other project delivery methods can also be intermixed, allowing many possible organizational schemes for the delivery of design and construction services that are suitable to a variety of owner requirements and project circumstances. Paying for Construction Services With fixed fee or lump sum compensation, the contractor or other construction entity is paid a fixed dollar amount to complete the construction of a project regardless of that entity’s actual costs. With this compensation method the owner begins construction with a known, fixed construction cost and assumes minimal risk for unanticipated increases in cost. On the other hand, the construction contractor assumes most of the risk of unforeseen costs but also stands to gain from potential savings. Fixed fee compensation is most suitable to projects where the scope of the construction work is well defined at the time that the construction fee is set, as is the case, for example, with conventional design/bid/build construction. As an alternative, compensation may be set on a cost plus a fee basis, JWBK274_Ch01.indd Sec1:18 where the owner agrees to pay the construction entity for the actual costs of construction—whatever they may turn out to be—plus an additional fee. In this case, the construction contractor is shielded from most cost uncertainty, and it is the owner who assumes most of the risk of added costs and stands to gain the most from potential savings. Cost plus a fee compensation is most often used with projects where the scope of construction work is not fully known at the time that compensation is established, a circumstance most frequently associated with construction management or design/ build contracts. With fixed fee compensation, the builder assumes most of the risk related to unanticipated construction costs; with cost plus a fee compensation, the owner assumes most of this risk. Between these two extremes, many other fee-structuring arrangements can be used to allocate varying degrees of risk between the two parties. Sequential versus Fast Track Construction In sequential construction (Figure 1.10), each major phase in the design and construction of a building is completed before the next phase begins. Sequential construction can take place under any of the project delivery methods described previously. It is frequently associated with design/ bid/build construction, where the separation of design and construction phases fits naturally with the contractual separation between design and construction service providers. Phased construction, also called fast track construction, aims to reduce the time required to complete a project by overlapping the design and construction of various project parts (Figure 1.10). By allowing construction to start sooner and by overlapping the work of design and construction, phased construction can reduce the time required to complete a project. However, phased construction also introduces its own risks. Since construction on some parts of the project begins before all design is complete, an overall cost for the project cannot be established until a significant portion of construction is underway. Phased construction also introduces more complexity into the design process and increases the potential for costly design errors (for example, if foundation design does not adequately anticipate the requirements of the not yet fully engineered structure above). Phased construction can be applied to any construction delivery method discussed above. It is frequently associated with design/ build and construction management project delivery methods, where the early participation of the construction entity provides resources that are helpful in managing the complex coordination of overlapping design and construction activities. 10/30/08 5:54:18 AM The Work of the Construction Professional: Constructing Buildings Construction Scheduling Constructing a building of any significant size is a complex and costly endeavor, requiring the combined efforts of countless participants and the coordination of myriad tasks. Managing this process requires an in-depth understanding of the work required, of the ways in which different aspects of the work depend upon each other, and of the constraints on the sequence in which the work must be performed. Figure 1.11 captures one moment in the erection of a tall building. The process is led by the construction of the building’s central, stabilizing core structures (in the photograph, the pair of concrete towerlike structures extending above the highest floor levels). This work is followed by the construction of the surrounding floors, which rely, in part, on the previously completed cores for support. Attachment of the exterior skin can follow only after the floor plates are in place and structurally secure. And as the building skin is installed and floor areas become enclosed and protected from the weather, further operations, such as the roughing in of mechanical and electrical systems, and eventually, the installation of finishes and other elements, can proceed in turn. This simple example illustrates considerations that apply to virtually every aspect of building construction and at every scale from a building’s largest systems to its smallest details: Successful construction requires a detailed understanding of the tasks required and their interdependencies. The construction project schedule is used to analyze and represent construction tasks, their relationships, and the sequence in which they must be performed. Development of the schedule is a fundamental part of construction project planning, and regular updating of the schedule throughout the life of the project is essential to its successful management. In a Gantt chart, a series of horizontal bars represent the duration of various JWBK274_Ch01.indd Sec1:19 Year 1 Jan Apr Jul Oct Year 2 Jan Apr Jul Oct Year 3 Jan Apr / 19 Jul SEQUENTIAL CONSTRUCTION Design Bidding Construction PHASED CONSTRUCTION Design Foundations Shell & Core Interiors Bidding Foundations Shell & Core Interiors Construction Foundations Shell & Core Interiors TIME SAVED Figure 1.10 In sequential construction, construction does not begin until design is complete. In phased construction, design and construction activities overlap, with the goal of reducing the overall time required to complete a project. tasks or groups of tasks that make up the project. Gantt charts provide an easy-to-understand representation of construction tasks and their relationships in time. They can be used to provide an overall picture of a project schedule, with only a project’s major phases represented (Figure 1.10), or they can be expanded to represent a larger number of more narrowly defined tasks at greater levels of project detail (Figure 1.12). The critical path of a project is the sequence of tasks that determines the least amount of time in which a project can be completed. For example, the construction of a building’s primary structural system is commonly on the critical path of a project schedule. If any of the tasks on which the completion of this system depends—such as design, shop drawing production and review, component fabrication, materials delivery, or erection on site—are delayed, then the final completion date of the project will be extended. On the other hand, other systems not on the critical path have more flexibility in their scheduling, and delays (within limits) in their execution will not necessarily impact the overall project schedule. The critical path method is a technique for analyzing collections of tasks and optimizing the project schedule to minimize the duration and cost of a project. This requires a detailed breakdown of the work involved in a project and the identification of dependencies between the parts (Figure 1.13). This information is combined with considerations of cost and resources available to perform the work, and then analyzed, usually with the assistance of computer software, to identify optimal scheduling scenarios. Once the critical path of a project has been established, the elements on this path are likely to receive a high degree of scrutiny during the life of the project, since delays in any of these steps will directly impact the overall project schedule. Managing Construction Once a construction project is underway, the general contractor or 10/30/08 5:54:18 AM 20 / Chapter 1 • Making Buildings Figure 1.11 In this photo, the construction sequence of a tall building is readily apparent: A pair of concrete core structures lead the construction, followed by concrete columns and floor plates and, finally, the enclosing curtain wall. JWBK274_Ch01.indd Sec1:20 10/30/08 5:54:18 AM The Work of the Construction Professional: Constructing Buildings / 21 Figure 1.12 In a Gantt chart, varying levels of detail can be represented. In this example, roughly the top three-quarters of the chart is devoted to a breakdown of preconstruction and procurement activities such as bidding portions of the work to subtrades, preparing cost estimates, and making submittals to the architect (a). Construction activities, represented more broadly, appear in the bottom portion (b). Figure 1.13 The critical path method depends on the detailed analysis of work tasks and their relationships to generate an optimal construction schedule. Shown here is a schematic network diagram representing task dependencies. For example, task 6 cannot begin until tasks 1, 4, and 5 are completed, and tasks 7 and 9 cannot begin until task 6 is finished. The dashed lines on the diagram trace two of many possible paths from the start to the end of the diagram. To determine the critical path for this collection of tasks, all such paths must be identified and the time required to complete each one calculated. The path requiring the most time to complete is the critical path, that is, the sequence of activities that determines the least time in which the collection of tasks as a whole can be completed. JWBK274_Ch01.indd Sec1:21 10/30/08 5:54:19 AM 22 / Chapter 1 • Making Buildings construction manager assumes responsibility for day-to-day oversight of the construction site, management of trades and suppliers, and communications between the construction team and other major parties, such as the owner and the designer. On projects of any significant size, this may include responsibility for filing construction permits, securing the project site, providing temporary power and water, setting up office trailers and other support facilities, providing insurance coverage for the work in progress, managing personnel on site, maintaining a safe work environment, stockpiling materials, performing testing and quality control, providing site surveying and engineering, arranging for cranes and other construction machinery, providing temporary structures and weather protection, disposing or recycling of construction waste, soliciting the work of subtrades and coordinating their efforts, submitting product samples and technical information to the design team for review, maintaining accurate records of the construction as it proceeds, monitoring costs and schedules, managing changes to the work, protecting completed work, and more. Trends in the Delivery of Design and Construction Services Improving Collaboration Among Team Members The design and construction industry continues to evolve, testing innovative organizational structures and project delivery methods in which designers, builders, and owners assume less adversarial and less compartmentalized roles. Such approaches share characteristics such as: • Contractual relationships and working arrangements that foster collaboration between project members JWBK274_Ch01.indd Sec1:22 • Participation of the construction contractor during the design phases of a project • Overlapping of design and construction activities to reduce the “time to market” • Expanded definitions of project services to encompass the full life cycle of a project—from its original conception, through planning, design and construction, to postconstruction occupancy—to better serve the needs of the building owner The growth of design/build in the construction marketplace is one example of this trend: Between 1980 and 2005 the share of private, nonresidential construction work performed as design/build construction increased from roughly 5 percent of the total market to an estimated 30 to 40 percent. Alternatives to traditional design/bid/build project delivery have gained increased acceptance in the public construction sector as well. Other new practice models, with such names as teaming, concurrent design, integrated practice, or alliancing, combine efficient project delivery methods with innovations in team member relationships in a variety of ways, with the aim of aligning all parties’ efforts with the shared goal of a finished product of the highest possible quality and value to the owner. Improving Efficiency in Production Other efforts within the construction industry focus on improvements in the efficiency of construction methods themselves. Unlike factory production, much building construction takes place outdoors, is performed within constrained and often physically challenging work areas, and is executed by a highly fragmented workforce. Despite the differences in these production environments, the construction industry is looking to lessons learned in factory production for approaches to improving the quality and efficiency of its own processes. Such so-called lean construction methods attempt to: • Eliminate wasteful activities • Structure the methods of production and the supply chain of materials and products to achieve the quickest and most reliable workflow • Decentralize information and decision making so as to put control of construction processes into the hands of those most familiar with the work and most capable of improving it Current estimates of labor inefficiency in building construction run as high as 35 to 40 percent, and estimates of materials wastage are 20 percent or more. The challenge of lean construction is to restructure the way in which construction materials and building components are manufactured, delivered, and assembled so as to reduce these inefficiencies and improve the quality of the delivered product. Improving Information Management Developments in information technology also are influencing the way buildings are designed and constructed. Most notable is building information modeling (BIM), the computerized, three-dimensional modeling of building systems. Unlike the two-dimensional representation of building systems characteristic of conventional computer-aided design (CAD), BIM involves an intelligent model. Components are not only represented geometrically, but are also linked to data describing their intrinsic properties and their relationships to other components. Originally developed for use in highly capital-intensive industries such as aerospace and automobile manufacturing, this modeling technology is now finding increased application in the design and construction of buildings. 10/30/08 5:54:20 AM Recurring Concerns BIM has the potential to impact many aspects of the building life cycle. It can aid the design team with the visualization and realization of complex geometries. It can improve coordination between design disciplines––for example, searching out “collisions” between mechanical system ductwork and structural framing or other such physical interferences between systems––and it can facilitate the modeling of building energy use and the performance of other building systems. For the builder, BIM can be used to improve coordination of trades, to drive the automated fabrication or preassembly of building components, and to integrate cost and schedule data more closely with building design. For the building owner, information accumulated in the model during design and construction can be carried forward for use with postconstruction building operations and facilities planning. As the implementation of BIM matures, it is expected to have a profound impact as a communication tool used to improve the coordination and sharing of information among all of the parties to a project. As the integrated building model is shared across the traditional boundaries of disciplines and project phases, the boundaries of responsibility between the designers, constructors, and owners will also blur, and new, more integrated relationships between these parties will likely be required to fully enable the potential of this technology. Recurring Concerns Certain themes are woven throughout this book and surface again and again in different, often widely varying contexts. Th