Secondary water resistance
What qualifies
Secondary water resistance (SWR) is a layer under the roof covering that keeps water from reaching the deck if the covering fails. Common qualifying products are self-adhering modified bitumen meeting ASTM D1970 and closed-cell foam adhesive applied to the underside of the sheathing. The material must cover the roof deck, not just valleys or eaves. A standard felt underlayment is not SWR.
Verification
Look for a product label, visible membrane at an edge or penetration, or foam on the attic side of the deck. Photograph the label and the location. If you cannot verify coverage, do not mark “yes.”
Worked example
The attic shows black, peel-and-stick membrane on the underside of the deck with a label reading ASTM D1970. That supports SWR. If the attic instead shows only asphalt-saturated felt under the shingles, that is underlayment, not SWR. The reasoning: the form requires a specific secondary layer, not any water-resistant paper.
Traps
- Accepting “we have a secondary barrier” without evidence.
- Confusing house wrap or felt with SWR.
- Seeing membrane in a valley and assuming full-deck coverage.
- Missing foam SWR because it is on the attic side.