by Kenton Shepard and Nick Gromicko, CMI®
The purpose of the series “Mastering Roof Inspections” is to teach home inspectors, as well as insurance and roofing professionals, how to recognize proper and improper conditions while inspecting steep-slope, residential roofs. This series covers roof framing, roofing materials, the attic, and the conditions that affect the roofing materials and components, including wind and hail.
During manufacturing, an adhesive strip of asphalt-like material is applied to the upper surfaces of the shingles. Once shingles are installed, these strips are designed to soften from the heat of the sun and bond to the shingles in the course placed above them.
The adhesive strip is the most important component in providing wind resistance for a shingle roof. Bonding shingles to each other helps them resist uplift and keeps them laying flat so that they expose the minimum amount of surface for the wind to push against.
This bond also helps seal the roof against moisture intrusion and allows the shingles to act, to some degree, as a single, water-resistant membrane.
Although adhesive strips are the single most important component in providing shingle wind resistance, there are no performance standards for them. Because there are no standards available, there are no manufacturing requirements, so this is an example of an area in which similar shingles from different manufacturers may perform quite differently from each other under identical circumstances.
This is an example of a higher-quality asphalt shingle with a 50-year warranty. On this particular model, the adhesive strip is installed on the back.
Here’s an example of a lower-quality, 20-year shingle with the adhesive strip installed on the face of the shingle.
If you compare close-up photos of the two adhesive strips, you can see that the adhesive strip of the higher-quality shingle is thicker.
Assuming that both shingles bond fully and that the adhesive strip material is of similar quality, the higher-quality shingle will have better wind resistance, partly due to the larger amount of adhesive.
In order to keep the adhesive strips from sticking to other shingles during storage, a strip of cellophane is installed on the underside of the shingles. These cellophane strips align with the adhesive strips while the shingles are in the package. Once shingles are installed, the cellophane strips no longer align with the adhesive, and the cellophane does not have to be removed. In fact, it should not be removed because it often carries printed information about the shingles.
Based on the information printed on this cellophane strip, you can see that this shingle manufactured by CertainTeed® complies with ASTM D3462, and that it’s approved for installation in Dade County, Florida, which is hurricane territory. Some cellophane strips list the impact rating, but unless you find spare shingles, you probably won’t be able to examine the cellophane strip anyway.
This one provides a little more information. It gives you the shingle model and tells you that it’s been rated Class 4 Impact-Resistant, which is the highest rating for this use.
Learn how to master a roof inspection from beginning to end by reading the entire InterNACHI series: Mastering Roof Inspections.
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Mastering Roof Inspections
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Inspecting Underlayment on Roofs
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