Does roof underlayment need to be glued down?
Mechanically fastened underlayment
- Synthetic: fastened with cap nails or cap staples, following the spacing printed on the roll. Closer spacing is used at laps and edges, and more fasteners are needed if it will be exposed for a while or in high wind.
- Felt: nailed, often with cap nails, with the laps the manufacturer and code specify. It tears more easily than synthetic and wrinkles when wet.
Neither is designed to be glued; adhesive is not part of their tested system, can trap moisture, and makes the next tear-off harder.
Self-adhered leak barrier
Peel-and-stick membranes are made of rubberized asphalt or similar compounds. They bond directly to a clean, dry deck and seal around the shanks of nails driven through them, which is why they are used where water concentrates:
- Valleys.
- Around chimneys, skylights, pipes and walls.
- Low-slope sections between 2/12 and 4/12.
- Along eaves in places where ice dams happen, such as parts of the North Georgia mountains.
They need minimum temperatures to stick well, and some decks or cold days call for a primer. Some products are rated for high heat under metal roofing.
Exposure limits
Every underlayment has a rated limit on how long it can sit in the sun before being covered, and wind can tear loose an under-fastened sheet, so good crews cover it promptly. See synthetic underlayment vs felt and ice and water shield in Georgia.
If you were asking about floor underlayment, the rules are different; this page covers roofs.