Why Chimney Flashing Leaks - And How a Real Repair Looks

When a customer calls about a ceiling stain near the fireplace, we already have a good idea what we will find. It is almost never the chimney itself and almost always the flashing - the metal that seals the joint where the chimney passes through the roof. Below are two chimney repairs we did in Mobile. Different houses, same story.

Job one: tar is not flashing

This is how we found the first chimney. Someone had smeared roofing tar along the joint instead of installing metal. Tar is a temporary patch, not a repair: it dries out in our heat, cracks within a season or two, and then water runs straight down the brick into the decking. Note the debris packed against the base too, holding moisture exactly where you least want it.

Water that runs behind bad flashing soaks the decking, and soft wood will not hold a nail or support new metal. We cut the damaged section out and set new plywood tight to the chimney. This is the step a cheap patch skips, because nobody sees it once the job is done.

And finished: step flashing marching up the slope, shingles woven back over the metal. Water hitting this chimney now has one path, down the roof and into the gutter.

Job two: a full rebuild, start to finish

A second chimney on a different house, photographed at every stage.

Same beginning: damaged decking out, new plywood in, fastened to the rafters.

Waterproof underlayment runs up the chimney and out onto the deck, creating a sealed membrane under everything else. If wind ever drives water past the metal, this layer sends it back out onto the shingles instead of into the house.

Then the flashing itself. Each piece laps the one below so gravity does the work, and the vertical leg runs up the brick face. No sealant holding the system together - the metal and the overlaps do that. Sealant is a finishing detail, not the structure.

Clean metal across the front and a proper corner where the two planes meet. That chimney is now sealed for the life of the roof.

Do I need a whole new roof?

Usually no. A flashing repair like either of these is a one-day job on a roof that is otherwise sound, and it costs a fraction of a replacement. If your roof is under 15 years old and the leak is confined to the chimney, we will tell you to repair it - we would rather be your roofer for the next twenty years than sell you one big job today.

Seeing a stain near the fireplace? Ask for a free inspection or call (251) 391-5262. We will get on the roof, photograph what we find, and show you exactly what we showed you here.

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