Roofing Wind Speed Ratings

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.

Roofing wind speed ratings.

In most cases using staples will void the manufacturer wind rating warranty. 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. 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. One thing to watch out for is an installer utilizing staples to install the roof.

This type of roofing material is classified based on windspeed resistance and with wind ratings categorized as follows. 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. 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. The height of the roof and exposure and risk categories are factors that are used to convert design wind speed to an uplift pressure.

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. The information is based on an. 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.

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. The same shingle qualifies for a 130 mph wind rating level 5 hurricane if you use 6 fasteners per shingle. 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. Wind speed maps and the rules to calculate wind pressures are found in section 1609 wind loads in the 2012 or 2015 ibc.