Mystery roof leak under chimney flashing driving me crazy


My roof is leaking under the chimney flashing. Leaking begins after at least 3 hours of constant moderate rain. I removed the drywall inside my house (destroyed by this leak) so I can see that the leak is indeed coming from underneath the chimney flashing. I went up on my roof with a hose and sprayed the whole roof area down with high pressure for 30 minutes - I was NOT able to make the roof leak. Leaking only starts after at least 3 hours of moderate rain - NOT necessarily even torrential rain. Where the eff is this leak coming from ? Could it possibly be coming from inside the chimney flue ? ripping my hair out ! thanks for any advice.


What type of chimney cap do you have and what kind of condition is it in?


chimney cap is cement. I noticed some hairline cracks so I completely sealed the chimney cap with “crown repair” product, which I was very pleased with. However, the next time it rained for several hours, my roof again leaked, so it does not appear to be coming from the chimney cap. Nor do the chimney bricks or mortar have any cracks - the brick and mortar appear to be in excellent condition.


one more potential clue: I’m seeing an unusual amount of efflorescence on the brick face of my chimney on the outside of my house, in the general area of the leak. Makes me suspicious that there might be leakage from the inside of the chimney somehow.


I agree with Axiom. From what you described, that usually is a chimney chase cover or the chimney itself leaking, not the flashing. I say usually, anything is possible.


Have you thought about getting a roofer out to look at it? Most guys will come and look at it for free.


Absolutely. I called 4 and believe Im in the queue. Theyre backed up for months here. Every house on my cul de sac (5) haf roofers looking at leaks during our rainstorms here (several !)


Are you able to post pictures of the chimney? Close and at a distance would be great.


picture 1 - showing efflorescence on brick under eave.


plane of brick face under flashing leaking into house


condition of chimney cap, chimney brick, and mortar


The cap and brick look good you probably need to replace the saddle and counter flashing, the mastic smeared on it gives it away.

Find someone to do this in copper that can be soldered.


I ran a strong stream of water down the sheet metal troughs for 30 minutes and watched it pool up - yet, NO leaking !

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So where is it leaking then?


Try the mortar joints


Brick chimney in the middle of a valley with a tile roof…OMG.
I hate tile roofs.
The rich mans disposable roof
Because they barely last longer than a shingle roof
Because the tile is in no way waterproof…
Rain resistant at best.
People are led to believe they have a lifetime roof.
Really Starting to hate Brick chimneys too!!!
For all the same reasons.
EVERY brick chimney eventually leaks.
EVERY single one…
Any brick chimney on a roof i replace with a house that is close to 60 years old, i cringe.


Agreed. That saddle looks rough. If you want to try to salvage it you could use something like GACO but that roofing tar that was slapped on there is a hot mess. If you encapsulate everything you see in GACO, you will probably be ok. It looks like some clown put spray foam in there where the shingle meets the flashing. That’s always a bad idea. Unfortunately, yours is the second one I’ve seen today like that.


U mentioned you soaked the chimney all at once, I’ve had positive results by starting at the lowest point on the chimney with water. Your going to need another person to let u know the minute you have water coming in. I also noticed the flue without the cap has jagged concrete that my have a small void.


I would buy some siloxane and and a pump sprayer coat the entire chimney top & chase. Two applications are better than one. Your statement that running water for 30 minutes with no sign of leaking indicates water is seeping through the mortar.


pic 1 mortar joints close up