Synthetic Underlayment

Underlayment's job never changes: it is the water-resistant layer rolled out across the deck before the shingles go on, standing between the wood and any water that gets past a lifted or missing shingle. What has changed is the material doing that job.

Synthetic underlayment is manufactured from woven or spun polymer material rather than paper soaked in asphalt, and that difference in raw material shows up in almost every practical way it performs on a roof.

It is significantly lighter per roll than felt, which means fewer rolls to carry up a ladder and faster coverage across a large deck, and its woven or coated surface resists tearing under foot traffic in a way felt simply cannot, an advantage that matters on a job that might stretch over more than one day.

Synthetic underlayment also tolerates sun exposure far better than felt before the shingles go over it. Felt paper can wrinkle or degrade if it sits exposed to UV and weather for more than a short window, while synthetic products are commonly rated to stay exposed for weeks without breaking down, which gives a crew more flexibility if weather delays the shingle installation.

Most synthetic products also have a printed grid pattern that helps installers keep straight, consistent shingle courses, a small detail that adds up to a cleaner, more accurate installation across a large roof.

Underlayment type is a fair, specific line to ask about on any estimate. It is completely hidden once the shingles go on, which makes it one of the clearer signals of whether a contractor is installing to a current standard or quietly saving money somewhere no one will ever see.