March 2002
Project Overview
The use of cold-formed steel in the structural system of residential construction has taken hold in
some site building markets but potentially offers far more value to the manufactured home industry.
The Manufactured Housing Research Alliance (MHRA) is coordinating an effort to develop a market
competitive structural design, based on cold-formed structural steel technology and suitable for the
home manufacturing environment. This report summarizes findings of the first phases of the
research. The effort is a cooperative undertaking of MHRA, the Manufactured Housing Institute
(MHI), several home manufacturers, the North American Steel Framing Alliance (NASFA) and the
US Department of Housing and Urban Development (HUD).
Home manufacturing has historically been a wood framed based industry. The HUD-code industry
has grown up around wood framing technology and significant time and expense have been invested
in value engineering wood as the structural material of choice. The manufacturing process is based
on lumber dimensions, material assembly methods and other building materials traditionally used in
conjunction with wood framing. However, relative to wood, cold-formed steel possesses a
compelling set of material properties. Steel is lightweight, fireproof, vermin resistant, dimensionally
stable (not subject to material decay, warping and twisting and shrinkage) and can be fabricated to a
wide range of shapes and sizes with virtually no material wastage.
There are additional factors that suggest the industry would be well advised to consider options to
wood as the basic structural building block. Foremost among these are the uncertainties associated
with future wood resources and the historic price fluctuations that at times have made wood more
expensive than steel. Even if steel proved to be less attractive than wood in the short term, as a future
alternative material, steel shows considerable promise.
This phase of the research was shaped by the following two overriding objectives:
- Demonstrate that it is possible to produce a cold-formed steel framed home at about the same
or at a lower first cost than a comparable wood framed system;
- Demonstrate that such a design can comply with the Federal Manufactured Home
Construction and Safety Standards.
In a process that started in 1998, the project team evolved a steel frame design that satisfied both
objectives. The major product of this study is a design for a prototype home, documented in this
report, consisting of a structural frame made entirely of cold-formed steel components that is cost
competitive with a comparable wood frame design. The design has been reviewed by a Design
Inspection Primary Inspection Agency (DAPIA)1 and deemed to be in compliance with the Federal
Manufactured Home Construction and Safety Standards (FMHCSS).
This research covers important ground and better defines those issues whose resolution is expected to
result in the economic and technical viability of steel frame for HUD-code applications. Additional
study is needed to more completely demonstrate that cold formed steel framing is competitive with
wood framing, and this work takes the necessary first steps in moving the technology forward.
The discussions that follow provide a history of the effort and a summary of the resources and
expertise invested in the study. Subsequent sections describe the prototype design together with
engineering documentation and recommendations for the subsequent steps required to demonstrate
the viability of steel for manufactured housing construction.
Prepared for:
U. S. Department of Housing and Urban Development
Office of Policy Development and Research
Prepared by:
Manufactured Housing Research Alliance
36 pages