Why is my roof leaking when the shingles look fine?
Most roof leaks start where something passes through the roof or where two surfaces meet. Common sources include cracked pipe boots, worn valleys, damaged step flashing, chimney flashing and missing kick-out flashing. These problems are usually hard to see from the ground and can often be repaired.
Pipe boots
Every plumbing vent on your roof has a rubber collar, called a pipe boot, that seals it to the roof. In the Texas sun, this rubber can crack after about eight to twelve years.
When a pipe boot cracks, water can run down the pipe into the attic and show up on a ceiling some distance from where it entered.
Valleys
A valley is where two sections of roof meet. Water from both sections drains through it, so a valley handles more water than any other part of the roof.
Valleys can leak when they were not installed correctly, when the underlayment beneath them is missing, or when leaves and debris collect in them and hold water against the shingles.
Where the roof meets a wall
Where a roof runs into a wall, step flashing should be installed with each row of shingles and covered by the siding above it. When this flashing is missing or installed incorrectly, water can get behind it.
Kick-out flashing matters too. It directs water into the gutter where a roof edge ends against a wall. Without it, water can run down inside the wall and cause damage that goes unnoticed for years.
Chimneys and skylights
A chimney needs flashing on all sides, and a cricket behind it if it is wider than about thirty inches. Sealant alone is not a long-term fix for chimney flashing.
Skylights have their own flashing, and the seals on a skylight often wear out before the roof around them.
Related questions
Is the leak directly above the stain on my ceiling?
Not always. Water often runs along the decking or a rafter before it drips, so the source can be several feet away from the stain.
Can I just seal the leak?
Sealant can stop a leak for a short time, but it is not a permanent repair. The source of the leak should be found and fixed.
How much does a roof leak repair cost?
Many single repairs, such as a pipe boot or a small section of flashing, cost a few hundred dollars. The price depends on access, roof height and how many problems are found.