Shingle wind rating exposed
ASTM D 3161 CLASSIFICATION FOR WIND RATING IMPORTANT FOR HIGH WIND AREAS IN COLORADO
The wind speed requirements for asphalt shingles are located in section R905.2.4.1 of the 2006 International Residential Building Code. The required ASTM D 3161 classification must be stamped on the shingle package. Most if not all 3 tab shingles are listed with this classification. The wind rated speed is listed on the package.
A Foundation for our company is that we study to show ourselves approved, a workman rightly dividing the truth. As additional information was provided to us by a local building department in Colorado we discovered important information.
The testing for ASTM D 3161 is performed by the manufacturer. The ICC evaluation reports substantiate the following conclusions. Each manufacturer has to follow guidelines in order for their shingle to meet ASTM requirements. This is a good thing.
The problem is that each shingle manufacturer wind tested their product on ¾” plywood sheeting. This is a big issue. Rarely is a home built in the United States that the architect would specify 3/4 “ decking, thus creating a problem of integrity with the ASTM certification.
In order for a 3-tab shingle that has a ASTM D 3161 classification meet that declaration it would have to be installed on ¾” decking, as a result most roofs that supposedly fall under this classification truly need to become declassified.