To secure roofing felt, you need to nail it down to the roof deck before adding shingles. Roofing felt is a layer that sits under your shingles and protects your home from water and wind damage. It acts like a backup shield if water gets past your shingles. Most roofers use felt as part of the standard roofing process. Getting it right keeps your roof working well for years. According to industry data, the average roof lifespan ranges from 25 to 50 years, so proper installation matters a lot.
What Tools Do You Need?
You will need a hammer, roofing nails, and a chalk line. Roofing nails have wide heads that hold the felt in place. A chalk line helps you keep rows straight and even.
Wear gloves and use a utility knife to cut the felt. You also need a ladder to reach your roof safely. Never work alone or in bad weather.
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How Do You Nail Down the Felt?
Start at the bottom edge of your roof. Unroll the felt and nail it every 12 to 16 inches. Place nails in rows going up the roof. According to RubyHome (2025), roof installation costs range from $4 to $40 per square foot, and proper felt installation is a critical part of that job.
Make sure each row overlaps the one below it by about 4 inches. This overlap keeps water from running under the felt. Space your nails evenly so the felt stays flat and tight.
Do not pull too hard when nailing. The felt should lie flat but not be stretched. Stretched felt can tear when your roof moves in heat or cold.
What About Felt Seams and Edges?
Seams need extra attention. Use a double layer at seams where two pieces of felt meet. According to This Old House (2025), the average U.S. roof size is 2,647 square feet, so you will have several seams to seal properly.
Tape seams with roofing tape or apply a roofing cement. This keeps water from getting between the layers. Edges around chimneys, vents, and roof valleys need felt too.
| Felt Installation Step | Nail Spacing | Overlap |
|---|---|---|
| Bottom row | 12-16 inches | 4 inches |
| Middle rows | 12-16 inches | 4 inches |
| Seams | 6-8 inches | Double layer |
When Should You Replace Old Felt?
If your roof is over 20 years old, the felt may be torn or rotted. According to RubyHome (2025), asphalt shingles last 20 years, and the felt underneath ages too. Replace felt when you replace shingles.
Check felt for rips, mold, or soft spots. Water stains on your ceiling mean the felt is failing. Installing new felt during a roof replacement keeps your home dry and safe.
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Talk with a local roofing company to review your options and get a detailed estimate for your project.