Roofing underlayment
What is roofing underlayment?
The water-resistant layer between the decking and the shingles — felt or synthetic — that’s a standard part of a complete reroof.
Definition
Underlayment is the protective layer rolled over the roof decking before the shingles go on. It comes as traditional felt or modern synthetic, and it adds a second line of defense against water that gets past the shingles.
A full reroof includes new underlayment, but scopes sometimes underprice it or assume the cheaper felt when synthetic is actually used. It’s a standard line item worth checking against the real job.
Underlayment works alongside ice-and-water shield, which handles the most vulnerable areas. Together they’re the waterproofing system beneath the shingles.
Related terms
Ice-and-water shieldA self-adhering waterproof membrane installed in vulnerable areas to prevent leaks from ice dams and wind-driven rain.Drip edgeA metal flashing installed along the roof’s edges that directs water away from the fascia — and a line item carriers frequently leave off.Supplement line itemsThe specific items added to a claim through a supplement — the missed materials, code work, and underpriced entries that bring the scope up to the real job.Scope of lossThe carrier’s itemized estimate of the damage and what they’ll pay to repair it — the document every claim is built on.