Why is my roof leaking around my chimney?
Short answer. Roof leaks around a chimney almost always come from the flashing system where shingles meet brick: counterflashing that has pulled out of the mortar or was only caulked to the face, rusted or missing step flashing on the sides, or no cricket on the uphill side, so water and debris pile up against the chimney. Less often, water enters through the crown or brick and shows up at the roofline.
Roof-side failure points
- Uphill side: the back pan or cricket. Without a cricket on a wide chimney, water dams there, and leaves and pine needles collect and hold it.
- Sides: step flashing rusted through at the bottom, or one long L-shaped piece instead of individual steps.
- Counterflashing: surface mounted and caulked to the brick, now cracked, or pulled out of its reglet.
- Front apron: lifted, short, or nailed where water runs.
- Shingles: cut too tight to the chimney or nailed through the flashing.
Signs to look for
- Stains on the ceiling or wall next to the chimney, especially upstairs.
- Wet framing in the attic at the chimney's uphill corners.
- Thick black roof cement smeared around the base, a sign of earlier patching.
- Debris piled behind the chimney.
The fix
Lasting repairs replace the system: a new apron, step flashing course by course, counterflashing cut into the mortar, and a cricket where the code calls for one, on chimneys wider than 30 inches measured parallel to the ridge. Sealant patches usually fail within a few seasons. A roof replacement is the ideal time to reflash, since the shingles are off. Robust Roofing's guide to chimney flashing leaks shows what that looks like.