ASTM D3161

ASTM D3161, Standard Test Method for Wind-Resistance of Asphalt Shingles (Fan-Induced Method), is published by ASTM International. It is one of the two test methods North American building codes accept for showing that asphalt shingles can stay on a roof in high winds. The other is ASTM D7158.

In the test, shingles are installed on a small sloped deck, allowed to self-seal under heat, and then exposed to a steady stream of air from a large fan for two hours. Inspectors look for any damage, including a sealed tab that has come loose. Any lifted or torn tab counts as a failure.

Classes

Shingles that pass are assigned a class according to the fan speed used:

• Class A – 60 mph (about 97 km/h)
• Class D – 90 mph (about 145 km/h)
• Class F – 110 mph (about 177 km/h)

Class F is the rating most often seen on shingle packaging and in high-wind specifications. The IBHS FORTIFIED Roof program, for example, accepts ASTM D3161 Class F or ASTM D7158 Class H shingles.

Limits of the test

The fan speed is a laboratory condition, not a forecast of how a roof will behave in a storm. NRCA's Professional Roofing magazine has pointed out that D3161 results do not correlate directly with in-service wind speeds, and the method takes no account of building height, terrain exposure, importance factor or risk category. For that reason designers in high-wind areas often prefer ASTM D7158, which ties its classes to the design wind speed method used in ASCE 7.

Use in codes

The International Building Code and International Residential Code require asphalt shingles to be classified for wind resistance. According to NRCA, the codes call for shingles with factory-applied self-sealing strips to be classified under ASTM D7158, while shingles without self-sealing strips may use D3161 classes; the required class depends on the design wind speed at the site. The product standard ASTM D3462 itself requires at least Class A (60 mph) wind resistance. In Canada, asphalt shingle product standards in the CSA A123 series and the National Building Code also reference wind testing. Outside North America, bitumen shingles in Europe are assessed under EN 544 and related CEN methods rather than D3161.

Reading a rating

A label reading "ASTM D3161 Class F" means a sample of that shingle passed the 110 mph fan test when installed to the manufacturer's standard instructions, which may include a specific nail count. Installing with fewer nails, on a damaged deck, or in cold weather that delays sealing can reduce real-world wind performance. Manufacturers often require a high-wind nailing pattern for their highest wind warranty levels.