Asphalt Shingle Roofs
No drip edge. If asphalt
shingles are installed without a drip edge, it's only a matter
of time before the plywood sheathing and fascia begin to rot.
Water dripping off the edges of the roofing is drawn by
capillary action to the exposed edges of the plywood
Install a metal drip edge at rakes and
eaves. The main purpose of a metal drip edge is to
interrupt the wicking of water to the sheathing edges.
incorrectly lapped under (instead of over) the metal
drip edge. Any water that may get under the shingles - for
instance, from wind-driven rain - should be carried by the felt
underlayment over the top of the drip edge.
Problem: Valley shingles were not tabbed or spotted
with roofing cement.
Lap the felt underlayment over the drip
The large volume of water that
collects in a valley can back up under uncemented shingles.
Solution: In a closed valley, embed valley shingles in
Always clip the top corner of the
valley shingles at a 45-degree angle. This prevents debris from
getting caught in the shingles and accumulating in the valley,
and it also directs water toward the valley centerline. For
extra protection, install a self-adhering eaves membrane under