Page 143 - 2018 National Home Improvement

2018 National Home Improvement Estimator, All Rights Reserved Page 118

• Roof blisters. Blistering (air pockets trapped between layers of roofing material) is a failure of the
bond. Punctured blisters are an obvious source of leaks.

• Splits in the membrane. Walk the area with your feet close together, taking many small steps.
Twist your feet as you walk. If a split is developing, you’ll see roof membrane separate between your
feet.

• Obstructed roof drains. Drains are made to carry water one way. When backed up, the roof will
leak.

• Deteriorated expansion joints. Seams on expansion joints may have to be replaced more often than
the roof itself.

• A leak when it isn’t raining. Condensate from roof-mounted coolers should be piped to a legal drain,
not discharged on the roof.

• Hundred year flood. It’s probably OK to ignore leaks first noticed after the heaviest rain of the
century or when rain is driven by unusually heavy wind. Neither you nor the present owner may be
around the next time that happens.

Flashing Leaks
If the roof surface appears sound, look for problems with the flashing. The term flashing is used to
describe two types of roofing material. One is metal flashing, which is used at roof joints, such as in the
valley of a hip roof where one surface meets another, or the metal counterflashing that extends down a
parapet wall and over the roof surface below. The other type is non-metallic flashing. It’s usually made
from asphalt-coated materials and adds an extra layer of protection under the roof cover, especially
along the eave line. In cold climates, roll-roof flashing helps prevent damage from ice dams, as shown in
Figure 7-1. Ice dams form when melting snow runs down the roof and re-freezes at the cornice. The ice
forms a barrier, causing water to back up under the shingles. A layer of 45-pound smooth-surface roll
roofing (flashing) won’t prevent the dam from forming, but it will minimize the chance of water entering
the attic and the wall below. Be sure this flashing extends 36" inside the warm wall. If two strips are
needed, seal the joint with mastic. Also seal the end joints with mastic. Note: Many building
departments require self-adhesive type roll roofing on eaves and gables.

Metal counterflashing is lapped over the top of bituminous base flashing to keep water above the roof
surface. The most common metal counterflashing problems are:
• Corrosion and deterioration of the metal.
• Open joints between pieces of metal flashing.