- Q.Is roofing felt
necessary under asphalt shingles?
A.Under asphalt shingles, #15 felt serves
three purposes: it provides a temporary cover for the roof
until the shingles go on; it protects the shingles from being
damaged by any pitch that bakes out of the sheathing; and it
provides a second line of defense if any shingles blow off.
Considering the relatively low cost, it is cheap insurance for
the last reason, even if the first two reasons don’t
In cold climates, where you are uncertain if the ceiling
insulation and roof ventilation is adequate, there is a strong
likelihood of ice damming. In this case, install an ice and
water shield along the roof edge, or two layers of #30 felt
bedded in asphalt.