Impact of Wind-Borne Debris Requirements on Construction Practices

Note: The proposed Florida Building Code allows the use of partially enclosed/internal pressure design for protecting buildings from the impact of wind-borne debris.

The Florida Building Commission contracted several studies to determine the impact of wind-borne debris requirements on construction practices and costs. Data sources are American Forest and Paper Association (AfoPA), Florida Concrete and Products Association and Southern Building Code Congress International (SBCCI). The following is a summary of those study results. (Note: this analysis only addresses exposure B.)

• •No change to wall framing practices in wind regions under 130 mph.
• •No change to masonry reinforcement practices in wind regions under 130 mph.
• •No change to roof framing and sheathing practices in wind regions under 130 mph.
• •Additional connectors required. Material costs for 1500 sq. ft. house under $100.
 

Frame Wall Construction:

The attached tables show that conventional framing, #2 spruce, pine, fir, 2x4 16 o.c. fully sheathed with minimum structural panel, is sufficient for partially enclosed/internal pressure worst case design up to 125 mph for 10' wall heights and 140+ mph for 8' wall heights. (AFoPA National Wood Design Manual, High Wind Edition, draft revised tables for compliance with ASCE 7-98) [See example attached.]

Masonry Wall Construction:

The Florida Building Commission approved the Florida Concrete and Products Association prescriptive design method, Guide to Concrete Masonry Residential Construction in High Wind Areas for construction of one and two family residential buildings for basic wind speeds of 130 mph or less and exposure B.

Roof Construction:

The engineering analysis of Gary Walker, P.E. and the Southern Building Code Congress International show that common frame roofing with #2 SPF, 2x6, 24" o.c. framing with 7/16" minimum structural panel sheathing is sufficient to withstand the additional forces of partially enclosed/internal pressure worst case design.

Connectors: Additional roof anchorage will be needed for basic wind speeds 110 mph and above.