How do you nail roofing felt?
Order of work
- Install drip edge along the eaves first.
- Install ice and water barrier where required or wanted, typically valleys and penetrations in Georgia.
- Roll the first course of felt along the eave, over the drip edge, keeping it straight and flat.
- Work up the roof, lapping each course over the one below, with horizontal laps of at least 2 inches and end laps of at least 4 inches, staggered from course to course.
- At the rakes, run felt to the edge, then install the rake drip edge over it.
Fasteners
Cap nails, roofing nails with a plastic or metal cap about 1 inch across, hold felt far better than bare nails, which tear through in wind. Some felts can be stapled when the manufacturer allows it. Place fasteners along laps and through the middle of each course, close enough that the sheet cannot billow. In most of North Georgia, below the code's high-wind threshold, the rule is to fasten enough to hold the felt in place until it is covered, following the felt maker's pattern.
Mistakes to avoid
- Overdriving fasteners so they tear the felt.
- Laying felt over wet decking, which traps moisture.
- Leaving felt exposed for days; Georgia sun and dew wrinkle it, and wrinkles telegraph through shingles.
- Walking on felt in the heat, which tears it.
- Reverse laps, where an upper sheet tucks under a lower one and channels water in.
Low slopes
On slopes from 2 in 12 to under 4 in 12, the code calls for two layers, laid with a 19 inch starter strip and 36 inch sheets overlapping 19 inches, or an approved alternative.
Many roofers now prefer synthetic underlayment, which handles exposure and foot traffic better. See synthetic underlayment vs felt and ice and water shield in Georgia.