Why is my chimney leaking into the loft or attic?
Short answer. Water on or around the chimney in the attic, sometimes called the loft, most often means failed flashing where the chimney passes through the roof, but it can also come through a cracked crown, porous brick, or an uncapped flue. Where the water appears on the chimney in the attic is the best clue to which one it is.
Read the wet spots
- Uphill side of the chimney. Water dammed behind the chimney is getting past the back flashing. Common on wide chimneys with no cricket.
- Down the sides. Step flashing that is rusted, too short, or was never woven into each shingle course.
- Downhill face only. Front apron flashing, or water running down the chimney face behind loose counterflashing.
- All around, with damp brick above the roofline. Water entering through the crown, mortar or brick and running down inside the masonry.
- Inside the flue or fireplace below. A missing cap or a cracked crown around the flue liner.
How to check safely
- Go up during or soon after a steady rain with a good flashlight. Stay on the framing.
- Look at the chimney masonry and the rafters and decking next to it for dark wood, drips and stains.
- Check insulation around the chimney for wet or matted areas.
- Note the side and height of the wetness, and take photos.
What else to look for
Wood framing should not touch masonry chimneys. Codes call for clearance between them, with the gap fire-blocked by noncombustible material. Charring or very dry, darkened wood next to the chimney is a fire safety concern for a chimney professional to evaluate.
Why it matters
Slow chimney leaks rot the decking and framing around the opening and soak insulation long before a ceiling stain appears.
See chimney leaks and crickets and roof flashing explained, and Robust Roofing's guide on why chimney flashing fails.