Resource Efficient Home Design: Wood Header Research - 7/3/2004 - Home Foundation Structure Framing

Resource Efficient Home Design: Wood Header Research

Wood framing is the predominant material in residential construction in the United States today, so its efficient use in homes is of paramount importance. Some parts of homes, such as headers, may be particularly over-designed, which affects cost and consumes more lumber than necessary. A recent study by the NAHB Research Center has resulted in a much more efficient way to design wood headers and similar beams.

Summarized below are some of the Research Center's findings related to the testing and evaluation of header systems.

• A typical No. 2 Spruce-Pine-Fir double header experiences a 10 to 20 percent bending strength increase, although such increase is currently not practiced;
   
• When a double top plate is placed over a header, the bending capacity of the header is effectively increased by a minimum of 5 percent; and
   
• When a 2x10 band joist, top plates, and above-story wall plate are located directly above the header, the header's effective bending capacity is increased by a factor of two or more.

It is important to note that header systems include not only the header (i.e., a double 2x member), but also the framing systems that surround the member. For example, when a floor band joist and other framing rests directly above the header, they contribute to the carrying of load over the wall opening below. Generally, this added strength is ignored in design. Also, the fact that multiple members are used can have a strength-enhancing effect beyond that currently recognized in approved design methods.

The complete findings of this research, which was performed in 1999 with funding from HUD, can be found in the NAHB Research Center report, "System Performance of Wood Header Assemblies."

For other information on the efficient design of wood headers and other framing systems in homes, the following resources may also be of interest:

• Cost-Effective Home Building: A Design and Construction Handbook (1994)
   
• Residential Structural Design Guide: A State-of-the-Art Review and Application of Engineering Information for Light-Frame Homes, Apartments, and Townhouses