Short answer
Start at the eave and roll the felt horizontally, each course lapping the one below by at least 2 inches and end joints by 4 inches (TAMKO’s numbers for felt under its roll roofing). Fasten it flat with cap nails or the fasteners your code allows, staggered and close enough that wind cannot lift it. Lay ice barrier at the eaves first where required, and cover the felt with roofing soon: it is not made for long exposure.
Before you start
Pick the underlayment: #15 or #30 felt, synthetic, or self-adhered in leak prone spots. Felt wrinkles when wet and tears in wind, so plan to cover it with roofing the same day or soon after (Fine Homebuilding).
What you need
How to install roofing felt, step by step
Clean and check the deck
Sweep the deck, drive or pull raised nails, and replace soft or damaged sheathing. The felt will show every bump.
Fit drip edge at the eaves
Nail metal drip edge along the eaves so the felt can lap over it.
Lay ice barrier where required
In ice dam areas, run self-adhered ice barrier from the eave to at least 24 inches inside the exterior wall line, measured horizontally. On most roofs that is two rows (Fine Homebuilding). Line valleys too.
Snap a line for the first course
Snap a chalk line one roll width up from the eave (less any overhang you want) so the first course runs straight.
Roll out and fasten the first course
Roll the felt along the line, keep it flat and free of wrinkles, and fasten it along the top and edges. Use cap nails or the fasteners your code allows, closely enough that wind cannot lift it.
Lap each course above
Work up the roof, lapping each course at least 2 inches over the one below. Where rolls end, lap them 4 inches (TAMKO) and stagger the end laps from course to course. Most felts have printed lines to guide the lap.
Lap over the ridge and at valleys
Carry each side over the ridge so the felt laps the other side. In valleys, run felt over the valley lining as your roofing maker’s detail shows.
Fit drip edge on the rakes
Install rake drip edge over the felt so water that runs off the felt goes over the metal, not behind it.
Cover it with roofing
Install the roofing as soon as you can. Felt is not made to face the weather for long.
Low slopes need more
On low slopes, one layer of felt can let wind driven water back up under laps. DECRA suggests two layers lapped about 19 inches on 3 in 12 to 4 in 12 roofs (DECRA), and shingle makers and codes have their own low slope rules. Check your roofing maker’s instructions and local code before you buy.
Next step: lay the roofing with how to install roll roofing.
Questions people ask
Which way does roofing felt overlap?
Like shingles: each upper course laps over the course below, so water running down the roof always runs over a lap, never into one. Start at the eave and work up.
How much should roofing felt overlap?
TAMKO’s roll roofing instructions call for at least 2 inches at the top laps and 4 inches at end laps. Some shingle makers and codes call for more, and low slopes can call for double coverage. DECRA suggests two layers lapped about 19 inches on slopes of 3 in 12 to 4 in 12.
Should I use staples or nails for felt?
Cap nails hold felt best and resist tearing in wind. Many codes and makers allow staples for felt; synthetics generally need cap nails or cap staples. Follow your local code and the underlayment label.
Does felt go over or under the drip edge?
The common order is drip edge on the eaves first with underlayment over it, and underlayment on the rakes first with drip edge over it. That way water always runs over each piece. Check your roofing maker’s detail.
How do I apply roofing felt adhesive?
Felt under roofing is normally fastened, not glued. Where an ice barrier is built from two layers of felt cemented together, or where a maker calls for cemented laps, use the asphalt cement the instructions name in thin even coats.
Sources
Last reviewed October 12, 2026. Products and listings change; check the data sheet and wrapper before you buy, follow the maker’s instructions, and check your local building code.