Tips for Applying Felt Paper to Roof Valleys

Roof valleys on sloped roofs need felt paper (also called asphalt paper) to provide a watertight seal under shingles. Here are tips for applying felt paper to roof valleys for a smooth, secure fit:

Use a Broad Strip of Felt Paper

Felt paper should extend at least 10 inches up each side of the roof valley, so use a strip between 20 and 24 inches wide.

Start at the Top

Lay the felt paper from the top of the roof valley to the eaves at the roof edge. You can center it and align it smoothly with the roof contours as you go down. Be sure the roof valley felt paper strip overlaps the other felt paper sections you have previously installed, by 1 inch or more per side.

Use Galvanized Staples

Attach felt paper to the roof sheathing, made of plywood, and to the framing strips with galvanized staples. These staples resist moisture and rust for a durable hold. Staple every 16 inches from the first framing strip to ensure you penetrate the sheathing and the strips through the felt paper.

Trim the Felt Paper at Top and Bottom

Use a box-cutting knife to trim off the felt paper at the eaves, and at the top peak of the roof valley.