Definition
A water-resistant layer rolled over the decking beneath the shingles, providing a secondary barrier against wind-driven rain and leaks.
Why this term matters for homeowners
In Greater Rochester, roofing terms usually connect to material grade, freeze-thaw and ice-dam risk, and whether repair or replacement is the smarter long-term spend.
- Use this term to ask better follow-up questions during estimates.
- Look for this language in Learn and Evaluate guides to connect definition to decisions.
- Confirm how this applies to your specific roof age, pitch, and home layout.
Related pages
Category: Roofing