TLDR: Most roof leaks start where something comes through the roof: a chimney, a vent pipe, or a wall. Water gets in at the flashing, runs along the wood, and shows up on a ceiling somewhere else. That is why the stain is a poor guide to the source.
We often hear from homeowners who have already had one or two roofers out for the same leak. The shingles looked fine, a patch went on, and the stain came back with the next heavy rain. In many of those cases the problem was never the shingles. It was a chimney or a vent.
Why these spots leak
A roof sheds water well across open slopes. The weak points are the places where the roof is cut to fit around something. Those joints are sealed with metal flashing and rubber boots, and those parts wear out faster than the shingles around them.
The usual causes
- Cracked pipe boots. The rubber collar around a plumbing vent dries out in the Texas sun and splits. Water runs straight down the pipe.
- Failed chimney flashing. The metal that laps up the sides of a chimney can pull away, rust through, or rely on old sealant that has cracked.
- No cricket behind the chimney. A wide chimney needs a small peaked diverter on its uphill side. Without one, water and debris pile up there.
- Loose or damaged vent covers. Wind can lift a vent or drive rain under it.
- The chimney itself. A cracked crown, missing cap, or worn mortar lets water in through the masonry, and it looks just like a roof leak.
Why the stain is not where the leak is
Water follows gravity and the easiest path. Once it gets under the roof it can run down a rafter or across the decking for several feet before it drips onto the ceiling. How to trace a ceiling leak back to the roof.
How we track one down
We start in the attic if we can get in, looking for water trails and stained wood above the ceiling stain. Then we check every penetration uphill from that point on the roof. We photograph what we find and go over the photos with you, so you can see the cause before any work is done.
Repair or replace?
Most chimney and vent leaks are a roof repair, not a new roof. New flashing or a new boot fixes the problem. If the leak has been going on for a long time, the decking under it may need attention too. More on rotted decking.
If it is leaking right now
Call us. We answer 24 hours a day and can tarp the area until it is dry enough for a permanent repair.
Live Oak Roofing has served San Antonio and the Hill Country since 2017. Inspections and estimates are free. Call or text (210) 460-8896, or request a free inspection online.