Roof leaks tend to happen in similar areas on most roofs. Being aware of the problem spots can help you quickly spot and diagnose possible leaks.
1. Roof Valleys
Leaks often originate in roof valleys, which are the lowest areas on the roof. Valleys are typically sealed against leaks with either a strip of metal flashing or with rolled roofing. Although leaks can occur as the flashing or rolled roofing wears out, more often, the culprit is that the end of the valley flashing is not cut to a point. When this happens, water flows along one side of the flashing until it reaches the end, then it flows beneath the flashing. The point will guide water off the roof.
2. Vent Boots
Your roof has several vents coming out of it. There are plumbing vents, attic vents, and vents for bathroom and kitchen fans. Around each vent is a rubber boot. If the rubber boot begins to degrade or if the seal fails, then a leak will develop.
3. Wall Flashing
There are two common types of wall flashing. Head wall flashing is installed where a shingled roof plane meets a wall with siding. Stepped flashings are similar, but the roof plane is at an angle to the vertical wall (similar to the type often seen at a chimney). Rust can put holes through the flashing, leading to leaks. Flashing that doesn't extend under the shingles far enough can also make the area more prone to moisture leaks.
4. Shingle Damage
Many leaks are simply the result of shingle damage. The damage may be visible, such as a puncture or tear on a shingle. It may be nearly invisible, such as the degradation of the surface that allows moisture through, which commonly happens to shingles following hail storms. Age can lead to shingle damage and leaks. For example, shingles often begin to curl up and deform as they reach the end of their useful lifespan.
5. Roof Dam Leaks
The most common type of roof dam is that caused by ice in the winter. An ice dam forms, typically at the roof edge, due to poor drainage. Often, issues with clogged gutters cause the dam formation. Water then backflows up the roof and under the shingles where it leaks into the house. Dams can also be the result of debris on the roof, like fallen leaves or heavy moss growth.
Contact a residential roofer if you suspect there is a leak on your roof. They can perform an inspection to locate the leak so a repair can be made.