Mystery roof leak under chimney flashing driving me crazy


pic 2 mortar joints on back of chimney close up


pic 3 mortar joints on third side of chimney close up


The mortar joints look pretty good to me - hardly any cracking at all. The brick does look pretty porous though.


I stuck a hose in this valley / trough leading down to the saddle and chimney flashing. I left a strong stream running for 30 minutes - completely pooling up the saddle area. I went and observed the leaking area inside my house and after 30 minutes there was absolutely no leak. I then sat on top of the chimney cap and sprayed the hose on both
roof faces draining toward my chimney - still no leak ! I sealed the chimney cap with some highly rated product and it appeared to seal well. The next long rainstorm resulted in more leaking from under the chimney flashing !


If you have the saddle replaced and done the way it should be water won’t pool up at all it will run off like it’s supposed to.

You do need to seal the chimney, mortar is not waterproof.

When it is difficult to pinpoint a leak you disassemble the most likely spot and go from there.

You did come here for experienced advice did you not?


Spray the tiles around the flashing for a while rather than just the flashing. See if it’s getting under the tiles and hitting the chimney through the underlay.


It could be an issue with the valley also. I am not a fan of such tight cut valleys on tile roofs, they can get clogged in unseen areas and divert water under the tiles.


One of the first things I tried… I sprayed all these tiles for 30 min


I blew out the valley with a leaf blower to make sure there were no blockages diverting water.


boggles my mind that I can’t duplicate the leaking after spending 30 minutes hosing down EACH section of roof:
1)the valley /saddle, 2) two different roof sections which drain into the chimney. We had several storms - each lasting about 36 hours with a few days in between to dry things out. the rain here is NOT by any means torrential like back east. yet after two or three hours, the roof starts leaking.


Those are pretty naive statements concerning tile roofs. I did my first Ludowici tile roof in 1982. It’s still in great condition, no leaks. Often we remove tile roofs that are 100 plus years because the flashings have deteriorated and are causing issues. We remove the tile then re-install. I’ve been on tile roofs in Italy that are 300 and 400 years old. Still working…


That was for Roof Lover by the way…


Yes, it does sound like a very frustrating situation. However I agree with Axiom about the saddle. If it was my house and I couldn’t find the leak the first thing I would do at this stage is redo the saddle. I would build it up a fair bit higher up the valley also to divert water better.

This is a very tricky thing to do (not diy), and honestly there are not many roofers I would trust to do the job other than myself so be careful when choosing a roofer.


p.s. I would also be removing the tiles in the valley to inspect that too.


The first thing that should be done is to seal the chimney, if that doesn’t work you need to start exploring.


I tried to seal the chimney last night - before our latest storm blew in. I wasn’t real happy with the only “brick sealer” I could find in Home Depot - something called “Sealcrete”. Well, I didn’t have a choice, so I bought some and sealed as much of the chimney above roof line I could reach. I see many siloxane based products on amazon - wide price range. Can anyone recommend a brick sealant in the $45 - $75 range ? thanks BTW, no leaking last night, but then the storm turned out to be pretty weak.


Does the brick we are seeing on the exterior go all the way through the roof decking and into the interior of the house and eventually become the brick you see around your fireplace?

If so, your counter flashing appears to be “saw-cut” into the brick when it should have possibly been “through wall” counter flashing integrated into the brick coursing.

Also, the valley that terminates behind the chimney and into the chimney cricket should stop about 3 or so feet further up the valley’s slope and a ridge board should go parallel to the ground into the corner of the chimney in order to provide proper slope for the cricket. The way it is now is way too small and does not divert water properly.


NO, I dont believe the brick structure goes all the way from roof through the interior of the house - ( cant see the structure without ripping walls out ).

The first floor and second floor fireplaces inside house look ornamental to me -brick only exists around hearth and doesn’t run to top of wall. What I can see from having ripped the ceiling out around the leak is that the interior flue structure is surrounded by drywall. On outside of house, brick structure runs 35 feet from ground to chimney cap.


another clue ? During the last long rainstorm, a second leak appeared about 4 feet up in the the middle of a wall of my bedroom - about 8 feet away from the opposite side of the chimney from the original leak ! So there is leaking both on the south side of the chimney under the flashing, and on north side of the chimney (8 feet north of the chimney under the roof. I sprayed this area down and also was unable to see any resulting leaking. WTF ?