Roofing Wind Speed Ratings

The height of the roof and exposure and risk categories are factors that are used to convert design wind speed to an uplift pressure.

Roofing wind speed ratings.

Class a for winds up to 60 mph class d 90 mph class f 110 mph class g 120 mph and class h 150 mph. For buildings with low slope roofs less than 2 12 slope the wind speed at eave height is used. Building owners and some specifiers and designers don t realize that the ratings apply to uplift pressures in pounds per square foot psf not wind speeds. 1 3 5 design pressure coefficients for roof zones.

Since local wind speed is the common factor in all three an understanding of how wind speed is used associated to each needs to be clarified. Wind speed maps and the rules to calculate wind pressures are found in section 1609 wind loads in the 2012 or 2015 ibc. A typical architectural laminate carries a 110 mph wind rating using 4 5 nails. Clay and concrete tile roofing has been tested in accordance with 2017 florida building code residential sixth edition to meet section r 4402 high velocity hurricane zones roof assemblies and rooftop structures with wind speeds up to 150 miles per hour.

Wind loads are based on the design wind speed which is based on the geographic location of the building height of the roof exposure category roof type enclosure classification and risk category. An ongoing issue that frustrates the industry as a whole is the confusion in how a roofing assembly will meet the building code will meet an uplift rating and be warranted based on local wind speeds. One common misconception is the belief that fm approvals windstorm classification ratings such as 1 60 1 90 or 1 120 correlate to wind speeds of 60 90 or 120 miles per hour mph. The information is based on an.

Building owners and some specifiers and designers don t realize that the ratings apply to uplift pressures in pounds per square foot psf not wind speeds. Roof design wind pressures are determined using the wind speeds at the mean roof height of the building i e average of the eave and ridge heights. One thing to watch out for is an installer utilizing staples to install the roof. One common misconception is the belief that fm approvals windstorm classification ratings such as 1 60 1 90 or 1 120 correlate to wind speeds of 60 90 or 120 miles per hour mph.