How do I find and fix a chimney leak?

I really feel like I've posted this thread before but I can't find it.... I'm going nuts.

Anyway, we have a very intermittent and persistent leak. From somewhere.

Our house is in Chicago. It rains a lot. But yet, we can go for months without seeing a drop here. In fact, a few years ago I took down the drywall, and made a fix to the flashing on the roof/chimney above. We didn't see any moisture at all for like 3 months before I put the drywall back up. 

I can't see any evidence of wetness in the attic above this. 

The house was reroofed and the exterior of the chimney was fully tuckpointed right before we moved in (June 2017), and then I made some fixes to the flashing above this in summer 2018 or 2019.

So, how do I go about finding and fixing the real issue?  About ready to just sledgehammer the whole thing down and rebuild the entire front of the house.

Stream of consciousness questions that will likely be relevant: Could it be a condensation issue? How is the Chimney cap? Was the issue there prior to the flashing repair? Is it possible the flashing repair didn't actually fix the issue? 

Likely a flashing failure at the chimney or leak up slope of the chimney. 

Is there a cricket installed in front of the chimney?   If not that is probably your best bet but involves carpentry and new shingles in that area/tie in. Alternately more DIY you could install rain diverters in a upside down V shape above which would minimize the water running down to the chimney. 

Hard to see in the photo, but tell me about the dark area.  Mold?  Moisture?  Something else?

Wipe it with a damp paper towel and smell it.  Mold mushroom smell?  Soot, burnt smell?  If your chimney flue (the liner) Has a crack in it then soot will permeate through the chimney brick and the wall.

If there is no evidence of a roof leak was the top of the chimney sealed around the flue tile?  Properly tuckpointing Masonry is an arduous  task, just saying?

Let me try to answer some questions. 

The flashing may not have fixed the issue, though the flashing was suspect. Cap could also be leaking, not sure best way to check. Could be condensation but we don't have fires in the fireplace (though we are planning a gas insert).

No cricket though I want to build one. Not sure it will fix the problem though or I'd be up there right now LOL.

Definitely water/wetness and not soot, since we don't have fires in there currently (so it's been at least 5 probably more like 10-15 years since last fire in there).

TRoglodyte said:

If there is no evidence of a roof leak was the top of the chimney sealed around the flue tile?  Properly tuckpointing Masonry is an arduous  task, just saying?

What is the flue tile? 

Given it only leaks sometimes, are there any common factors when it does leak? Ie' higher than usual rain volume, lots of wind, hail... That soft of thing.

I'm thinking something along the lines of wind driven rain getting under a flashing that is normally "adequate", a bank of hail sitting and melting in a position that might be unusual compared to regular rain or just  huge rain dump not getting awy from the area as quick as it might in lighter rain and therefore exposing a less than perfect flashing join or similar.

i assume crawl space is limited/ borderline non existent given the chimney is on the outer wall?

A masonry chimney is 2 distinct separate parts, the inner part goes from the firebox to a high temperature flue tile that vents the smoke. The bricks you see are simply a wrap to marry it to the house. If it is leaking at the tippy top where the smoke exits water could migrate, pool, and weep under the roof. A good chimney sweep may help?

Having previously fought this battle with our fieldstone chimney; Pay a chimney person to inspect and likely replace all the flashing which was likely not done right to begin with. 

They'll probably want to re-flash, tuck point any problem mortar, seal the sides and seal the cap to be sure. Water does funny things in chimneys. I failed 3 times to fix our issue...

And lastly chimney work is an area where you get what you pay for. Im 99.9% a do it myself person but I was happy to pay what felt like an exorbitant amount of money after the first sideways rain our ceiling stayed dry.

What does the intersection between the roof and the chimney look like? Our chimney is huge (like 8' or more across) and the roof met it on the eave end of things so it was dead flat all the way across. Coupled with that it was right where a roof valley drained so a ton of the water from two roofs was stalling out right where the chimney is. We were just buying the house and it needed a new roof and the roofer looked at it and - without having been inside - said "I bet you have a roof leak right here." Right he was - the ceiling had caved in the leak was so bad. He made a few suggestions but the easiest and cheapest one was to frame a small side slope in that added good drainage for the water to get past the chimney. He roofed it with rubber since it was low slope but you can't see it from the ground and we haven't had one drop of water from that in the seven years we've lived here.

Look above the chimney for a leak, a lot of times it's a leak a foot or so above where you see water when you can't find it.

Personally I have good luck with a ridiculous level of Thru The Roof slathered anywhere in the vicinity and a few feet in every direction for fast repairs

Is there any plumbing in the ceiling between floors?  (I'm wrestling that alligator now)  =~ (

Cchambers13 said:

And lastly chimney work is an area where you get what you pay for. Im 99.9% a do it myself person but I was happy to pay what felt like an exorbitant amount of money after the first sideways rain our ceiling stayed dry.

Just be careful, the price could be.... through the roof.

I'll see myself out.

In reply to Mr_Asa :

Better than seeing the money spent on the chimney leak... go up in smoke.

I'll hold the door for you.

Well all jokes aside, I think I might try some epoxy or sealant for the cap. I can also climb back up there to re check the flashing. 

Here's an outside shot to show some more info. 

Now that I look, the previously fixed crack in the cap could be questionable.

I'll bet your trouble is on the side that can't be seen from the ground.  This lack of visibility from the ground could also aid with the repair meaning that the repair doesn't have to aesthetically look fantastic since it wont be seen.

My wife sometimes laments that she wishes we had a fireplace,  For me, the lack of a fireplace was one of the things that attracted me to our house.  I've had houses with fireplaces before and rarely/never used them.  

If there is no cricket, that is an awfully wide bit of masonry to seal properly with flashing.  

How wide is the fire box on your fire place? I think I see 4 flue tiles exiting that chimney, 3 round 1 square? does your furnace feed one from the basement?

In reply to TRoglodyte :

I think it's 30 inches wide (assuming I'm quoting the part you're referencing).

Re: cricket, yes I agree that would be a big improvement. But I'd love to prove or disprove that before diving into it if possible. 

As far as the chimney itself, yeah at one point the furnace went through there. There are 2 pcv pipes in the right most one that would be for probably a non-original furnace, and they aren't even in use anymore (but but the current furnace uses the questionable practice of only running an exhaust vent, so I might be changing that setup anyway).

We really don't use the chimney at all, except for the planned gas insert in the future. Yes it's probably a huge source of cold air directly to our basement in the winter lol.

Post a photo from the high side. If there is no sloped "cricket" where the main slope meets the chimney - I'll bet my lunch the sheet metal flashing "saddle" has a joint in the flat area - and that joint is the location of your leak.

Second concern is that brick is like a wick. If you simply stick flashing to the face or even cut in a notch and tuck the flashing in, water (sideways rain) can still migrate through the brick and end up inside. Right where your ceiling is wet.

..leaks suck. 

Finally climbed up there to get more photos.

No cricket, but the flashing seems good - no vertical joints I can see.

Now, there were some possible issues I see. Here are some places the Shmoo may not have sealed well.

And also the cap looks a bit rough to me. I'm especially concerned about how the chimneys look to be deteriorating.

Obviously someone has been up here sealing stuff before. Maybe that is a clue?

Other ideas?

That looks like a relatively new roof. I can't believe the roofer didn't explain the problem with a WALL against the downhill edge.
 

There is no easy way for water and snow and ice to get around your chimney. It just hits the wall. Literally. Water likes an easy path over the edge so normally you have a "cricket" which just means a couple sloped planes on the uphill side with a small ridge perpendicular to the chimney. 
 

But amazingly.. that might not be the problem here.
 

I think I'd take out the low hanging fruit first. Patching the big HOLE next to the two pvc pipes would be task #1. Then tool some "Shmoo" (your word) into the visible gaps at the top edge of the white sheet metal. Then do the same on any visible cracks on the top and on the face of the brick.
 

Then get a garden hose and spray water onto the shingles for ten minutes and see what happens. If nothing happens spray some water on the cap and the brick for ten minutes and see what happens. 
 

Edit: the concrete cap looks rather rough also. You might try to find a concrete patch and repair product. I don't know a suitable one off the top of my head but I'm sure Google can find one. 

Seems like a good place for caps: