Here’s how to do it.
Most local codes call for using 30-pound felt.
Underlayment, flashings, and shingles all work together and must be installed in the correct order.
If you better temporarily protect a roof, cover it with plastic sheeting or a tarp.
Where the drip edge meets a valley or a hip, cut the pieces with overlapping tabs.
Press the tabs firmly to make crisp corners with no gaps and attach them with roofing nails.
Align the Felt
Snap a chalkline to help you align the WSU or felt.
Often it’s possible for you to re-roll it, then unroll it while peeling off the paper backing.
Avoid creases and stay aligned with the chalkline.
Press down to tightly seal the WSU.
Snap chalklines on both sides for guides.
Roll out and smooth the WSU and drive a few nails on one side to hold it temporarily.
Fold over the other side and peel off the paper backing.
Press it into place, remove the nails, and peel off the paper on the other side.
Stay Parallel
Overlap felt courses at least four inches.
Roll out the felt, eliminating creases or bubbles, and drive at least three staples every foot.
(Rather than cutting the felt horizontally to fit, overlap it by more than 4 inches.)
Apply felt on the ridge so it overlaps at least 8 inches on each side.
Eliminate creases and bubbles.
Pry away the siding and slip the felt under the siding.
