Short Answer
Potential causes include damaged flashing, counterflashing, masonry deterioration, crown problems, sealant failure, and roof intersection issues.
Detailed Explanation
Chimneys are complex penetrations through the roof, and they have multiple potential leak sources. The most common include: damaged or deteriorated step flashing where the roof meets the chimney sides; missing or failed counterflashing (the flashing embedded in the mortar joints of the chimney); masonry deterioration (cracked bricks, deteriorated mortar joints) that allows water to enter through the chimney itself; crown problems (the concrete cap at the top of the chimney that can crack and allow water in); sealant failure at flashing or crown joints; and roof intersection issues where the chimney meets the roof at a vulnerable angle. Chimney leaks require careful diagnosis because the water source could be the flashing, the masonry, the crown, or a combination.
Why It Matters
Chimney leaks are often misdiagnosed as roof leaks. Proper diagnosis identifies whether the problem is the roof, the flashing, or the chimney structure itself.
When Repair Makes Sense
The leak is caused by flashing or sealant failure that can be corrected without masonry work.
When Replacement Makes Sense
The masonry is severely deteriorated, the crown is cracked, or the chimney structure itself is compromised.
Questions to Ask Your Contractor
- ?Is the leak from the flashing, the masonry, or the crown?
- ?Does the chimney need masonry repair or just reflashing?
- ?Is the counterflashing intact?
- ?Is the crown cracked or deteriorated?