Roofing Glossary

Roof Underlayment

Roof underlayment is the water-resistant sheet material rolled out over the bare decking before shingles go on. Think of it as the roof's second line of defense: if wind drives rain under or between shingles, the underlayment is what keeps that water off your wood deck.

Underlayment also protects the deck during installation, provides a uniform surface for shingles, and adds a backup barrier in ice dam and wind-driven-rain situations. It is a required component of virtually every shingle manufacturer's system — skipping it voids warranties.

The two main types are traditional asphalt felt and modern synthetic underlayment. Both do the same job, but synthetics are lighter, stronger, and far more tear-resistant during installation, especially in wind.

Why It Matters

Homeowners never see underlayment, but it does critical work during the worst weather. When comparing quotes, confirm which underlayment is specified — it is a legitimate quality differentiator, not just line-item filler.

A Maryland Note

In Maryland's wind-driven coastal rains, underlayment earns its keep. Synthetic underlayment's tear resistance is a real advantage during installations on breezy days.

Questions about your own roof? Request a free estimate or call Nucci Brothers Roofing at (301) 458-1003.