Roofing Wind Speed Ratings

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.

Roofing wind speed ratings.

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. 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. 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.

In most cases using staples will void the manufacturer wind rating warranty. 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. 1 3 5 design pressure coefficients for roof zones.

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. 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 same shingle qualifies for a 130 mph wind rating level 5 hurricane if you use 6 fasteners per shingle.

The height of the roof and exposure and risk categories are factors that are used to convert design wind speed to an uplift pressure. The information is based on an. A typical architectural laminate carries a 110 mph wind rating using 4 5 nails. This type of roofing material is classified based on windspeed resistance and with wind ratings categorized as follows.