High Wind Resistant Concrete Construction in IRC

Prescriptive design provisions in the 2003 IRC for light-framed construction (wood or light gage steel framing) are applicable to areas where the basic wind speed is less than 110 mph (3 second gust).

In the 2006 IRC, prescriptive provisions for light-framed construction are applicable to hurricane prone regions where the basic wind speed is less than 100 mph and areas outside hurricane-prone regions where the basic wind speed is less than 110 mph. In order to design buildings of light-framed construction in the higher wind areas beyond the scope of the IRC, standards referenced in the code are required. No special publications or resources are required for one- and two-family dwellings and townhouses constructed using concrete exterior walls as long as the homes meet the parameters contained in the IRC.

Walls constructed using Insulating Concrete Forms (ICF) and conventionally formed concrete are addressed by Sections R611 and R612, respectively, of the IRC.

The parameters are:
 Maximum building height is two stories, plus basement.
 Maximum unsupported wall height within a story is 10 feet.
 Maximum plan dimension is 60 feet.
 Floors spans are not greater than 32 feet.
 Roofs spans are not greater than 40 feet.
 Maximum wind speed is 150 mph.
 Seismic design categories (SDC) are A, B, C, D0, D1, or D2.
 For townhouses assigned to SDC C and all buildings assigned to SDC D0, D1 or D2, there must not be any irregularities.

For concrete construction, the IRC defines a building as being irregular where:
1. Exterior shear wall lines are not in one plane vertically from the foundation to the upper most story. 
2. A section of the floor or roof is not laterally supported by shear walls or braced wall lines on all edges.
3. An opening in the floor or roof is the smaller of 12 feet or 50% of the least floor or roof dimension.
4. Portions of a floor level are vertically offset.
5. Shear walls do not occur in two perpendicular directions.

In addition, for townhouses assigned to SDC C and all buildings assigned to SDC D0, D1 or D2, the building shall be rectangular with a maximum aspect ratio of 2, it shall have no cantilevers or setbacks, the weight of interior and exterior wall finishes must not exceed 8 psf, and the gable portion of walls must be constructed of light-frame construction,

American Concrete Institute Building Code Requirements for Structural Concrete  (ACI 318) should be used for the design of buildings or sections of buildings that are determined to be irregular or that are not within the parameters described.

Provisions for high wind resistant masonry construction are provided in the Southern Building Code Congress International Standard for Hurricane Resistant Residential Construction (SSTD 10); a reference standard in the IRC.  The provisions of SSTD 10 may also be used for concrete construction.

There is no reason to delay construction of homes with concrete.  There is no waiting for the development of special user friendly guides or to obtain additional manuals for high-wind resistant concrete construction.  For many homes the prescriptive requirements for concrete construction are in the body of the IRC. [ return to top ]