Chimney Repair and Flashing in Knoxville.

Why does the chimney leak more than the rest of the roof?

Every other penetration in a roof is small and round and easy to seal. A chimney is a large masonry structure passing through the roof plane at an awkward angle, moving at a different rate than the roof around it, with four separate sides that each need a different detail. That is why flashing problems at the chimney are the most common cause of a roof leak around one, and why a leak near a chimney is a chimney leak until proven otherwise.

What are the parts of chimney flashing?

• Step flashing. Individual L-shaped pieces woven in with each course of shingles up the side of the chimney. Each one laps the one below so water steps down and out. Get one wrong and you have built a funnel.
• Counter flashing. The layer let into the masonry itself, covering the top edge of the step flashing so water cannot get behind it. This is what fails when someone has caulked a chimney instead of flashing it.
• The cricket. A small peaked structure on the uphill side of a wider chimney that splits water and sends it around instead of letting it pond against the masonry. Wider chimneys need one, and a surprising number do not have one.
• The crown. The sloped concrete cap on top. Cracks in the crown let water into the chimney structure from above, which is a completely different leak path from the flashing.
• The cap. A missing chimney cap lets rain straight down the flue.

What does the freeze-thaw cycle do to chimney brick?

East Tennessee winters are not severe, and that is the problem. Genuinely cold climates stay frozen. Knoxville cycles: water soaks into masonry and mortar during a wet spell, freezes overnight, expands, thaws the next afternoon and soaks in a little deeper. Repeat that through a winter and you get spalling, where the face of the brick flakes away, and deteriorated mortar joints. Deep gaps or missing sections of mortar let water fall straight inside the chimney.

Which is why chimney work is a roofing conversation as much as a masonry one. Chimney repair is on the service list, and the flashing detail is part of any roof replacement rather than an afterthought.

What to do about a stain near the chimney

Get it looked at before it spreads, because the leak is not where the stain is. Water tracks along rafters and decking before it shows up on a ceiling, so by the time you can see it, it has been wet up there for a while. A free roof inspection finds the entry point rather than guessing at it. Call (865) 813-8020.