Feature Question

The Atlantic Station in Atlanta, GA was completed in 2005 and includes over two million square feet of wood-framed buildings.  Wood not only provided versatility in design but a cost effective option for high density housing.  For more information on the Atlantic Station project, a case study is available from APA – The Engineered Wood Association (www.apawood.org, publication J130).

What’s the maximum height and area allowance for a wood structure?

Before the adoption of the 2000 International Building Code (IBC), building with wood was restricted to Type V construction. This meant wood structures were limited to two to three stories, depending on the subcategory, and the allowable square footage to less than 9,000 or 18,000 square feet respectively, as shown in Figure 1.

However, the 2000 IBC expanded wood use to Type III construction, which allows wood structures that are four and five stories and up to 19,000 and 28,500 square feet respectively.  Type III construction is similar to Type V except that the exterior walls are required to be built with fire retardant-treated materials as stated in section 602.3 of the 2006 IBC.

In addition to the increased flexibility provided by Type III construction, the 2000 IBC also introduced new sprinkler regulations for all building types which can increase a wood structure’s footprint by 200 to 300 percent. Sprinklers also allow for open frontage increases which can grow the footprint by an additional 75 percent. If you’re able to include sprinklers in a Type III building, then your structure can be up to five stories high with each story covering over 100,000 square feet.

Figure 1: Excerpt from IBC Table 503 ALLOWABLE HEIGHT AND BUILDING AREAS

The American Wood Council offers a free online calculator for determining height and area allowances for buildings of various occupancies and fire protection based on the 2006 IBC. Available at www.awc.org, it allows users to input their design variables and quickly identify the types of construction suitable for wood.

For more information on how to build non-residential structures out of wood more easily and at less cost visit http://www.woodworks.org. If you’d like to submit a question for a future issue of the WoodWorks e-newsletter, please email Ivana Kraljevic at Ivana@woodworks.org.