Staining on the ceiling around the chimney

The chimney-to-roof junction is the most common roof leak point on any house. Before anyone sells you masonry work or a waterproof coating, make sure the flashing has been checked.

1Why it leaks there

• Flashing. The chimney and the roof move differently. Flashing bridges the gap, and over time it loosens, corrodes, or was never stepped and counter-flashed properly.
• Caulk instead of flashing. A bead of sealant smeared over the joint is a short-term patch. It dries, cracks and lets water in.
• The uphill side. On wider chimneys, water and debris pile up behind the chimney unless a cricket (a small peaked diverter) sends it around.
• From above. Less often, water gets in through a cracked crown, an open flue or porous brick and shows up in the same spot.

2How to check what you’re dealing with

1. Note when it shows upStains after wind-driven rain point to flashing. Stains after any rain, or in the firebox, can mean an open flue or crown.
2. Look in the atticWith a flashlight, look at the roof deck and framing around the chimney for wet wood, staining or daylight.
3. Look from the groundWith binoculars, look for lifted metal, heavy caulk, missing mortar at the flashing line, or no cap.
4. Check the stain itselfMark its edges. If it grows after the next storm, the leak is active.

3Fixing it

4What drives the cost

Flashing repair costs depend on the chimney’s size, the roof’s pitch and height, the roofing material, whether a cricket is needed, and whether wood around the chimney has rotted. Ask for photos of the failed flashing with the quote.

Chimney cost

6Related chimney problems

• No cap on the flue
• Cracked crown at the top
• Unlined flue on an older chimney
• Creosote build-up in a wood-burning flue
• Carbon monoxide alarm sounding
• Spalling brick on the exterior stack
• Gas appliance venting into an old flue

Back to Chimney.