February 2000
Preface
Structural Design Guide is a unique and comprehensive tool for design professionals,
particularly structural engineers, seeking to provide value-added services to the producers
and consumers of American housing. As such, the guide is organized around the
following major objectives:
- to present a sound perspective on American housing relative to its history,
construction characteristics, regulation, and performance experience;
- to provide the latest technical knowledge and engineering approaches for the
design of homes to complement current code-prescribed design methods;
- to assemble relevant design data and methods in a single, comprehensive
format that is instructional and simple to apply for the complete design of a
home; and
- to reveal areas where gaps in existing research, design specifications, and
analytic tools necessitate alternative methods of design and sound engineering
judgment to produce efficient designs.
This guide consists of seven chapters. The layout and application of the various
chapters are illustrated in the figure on page vii. Chapter 1 describes the basic substance
of American housing, including conventional construction practices, alternative
materials, building codes and standards, the role of design professionals, and actual
experience with respect to performance problems and successes, particularly as related to
natural hazards such as hurricanes and earthquakes. Chapter 2 introduces basic
engineering concepts regarding safety, load path, and the structural system response of
residential buildings, subassemblies, and components to various types of loads. Chapter 3
addresses design loads applicable to residential construction. Chapters 4 and 5 provide
step-by-step design procedures for the various components and assemblies comprising
the structure of a home—from the foundation to the roof. Chapter 6 is devoted to the
design of light-frame homes to resist lateral loads from wind and earthquakes. Chapter 7
addresses the design of various types of connections in a wood-framed home that are
important to the overall function of the numerous component parts. As appropriate, the
guide offers additional resources and references on the topics addressed.
Given that most homes in the United States are built with wood structural
materials, the guide focuses on appropriate methods of design associated with wood for
the above-grade portion of the structure. Concrete or masonry are generally assumed to
be used for the below-grade portion of the structure, although preservative-treated wood
may also be used. Other materials and systems using various innovative approaches are
considered in abbreviated form as appropriate. In some cases, innovative materials or
systems can be used to address specific issues in the design and performance of homes.
For example, steel framing is popular in Hawaii partly because of wood’s special
vi Residential Structural Design Guide
problems with decay and termite damage. Likewise, partially reinforced masonry
construction is used extensively in Florida because of its demonstrated ability to perform
in high winds.
For typical wood-framed homes, the primary markets for engineering services lie
in special load conditions, such as girder design for a custom house; corrective measures,
such as repair of a damaged roof truss or floor joist; and high-hazard conditions such as
on the West Coast (earthquakes) and the Gulf and Atlantic coasts (hurricanes). The
design recommendations in the guide are based on the best information available to the
authors for the safe and efficient design of homes. Much of the technical information and
guidance is supplemental to building codes, standards, and design specifications that
define current engineering practice. In fact, current building codes may not explicitly
recognize some of the technical information or design methods described or
recommended in the guide. Therefore, a competent professional designer should first
compare and understand any differences between the content of this guide and local
building code requirements. Any actual use of this guide by a competent professional
may require appropriate substantiation as an "alternative method of analysis." The guide
and references provided herein should help furnish the necessary documentation.
The use of alternative means and methods of design should not be taken lightly or
without first carefully considering the wide range of implications related to the applicable
building code’s minimum requirements for structural design, the local process of
accepting alternative designs, the acceptability of the proposed alternative design method
or data, and exposure to liability when attempting something new or innovative, even
when carried out correctly. It is not the intent of this guide to steer a designer unwittingly
into non-compliance with current regulatory requirements for the practice of design as
governed by local building codes. Instead, the intent is to provide technical insights into
and approaches to home design that have not been compiled elsewhere but deserve
recognition and consideration. The guide is also intended to be instructional in a manner
relevant to the current state of the art of home design.
Finally, it is hoped that this guide will foster a better understanding among
engineers, architects, building code officials, and home builders by clarifying the
perception of homes as structural systems. As such, the guide should help structural
designers perform their services more effectively and assist in integrating their skills with
others who contribute to the production of safe and affordable homes in the United
States.
Prepared for
U.S. Department of Housing and Urban Development
Office of Policy Development and Research
and
National Association of Home Builders
Housing Affordability Through Design Efficiency Program
434 pages
Purchase a hardcopy of this report from the NAHB Research Center's bookstore.