How to seal leaky artificial stone chimney?

[jlaustin]

I have a metal double-wall flue that runs from my fireplace through the roof. It exits through a "fake" chimney ... i.e., the chimney looks like it is made of stone. As I understand the construction, it is essentially a box built from wood framing and plywood, then some sort of coating was applied, then artificial/cast stones were applied and grouted. I saw some of the construction process and I'm certain that flashing was applied where the chimney meets the architectural shingle roof.

Immediately after construction, there was a slight leak noted in the attic around the framing of the chinmey where it joins the roof. Someone did the usual "apply sealant where it looks like it might be leaking" routine, and supposedly, it was fixed. A little later, it was obvious that it was still leaking - the builder theorized that the artificial stone might be imperfectly grouted and water might be leaking behind the "stone" and running down. He had a clear sealer applied to the entire "stone" surface, and this seemed to help. It's really difficult to tell about leaks - seemed to leak with some rains and not with others - probably has something to do with which way the wind is blowing, etc.

Anyhow, we're a couple of years out from the sealant application and just had some really heavy rains. Thought it would be a good time to check the attic and sure enough, it appeared to be leaking worse than ever! I'm now got about 5 strategically placed plastic buckets up there! The leaks are slow, but definitely there - it's hard to pinpoint since water can run along framing and drip several feet from its origin. They definitely emanate from the area where the chimney joins the roof and I think it leaks on more than one side - up inside the "box" it is dry as a bone. We have very thick stabilized cellulose insulation, so I think it has absorbed most of the water, so no ceiling damage ... so far.

Obviously, I want this definitively fixed! Any new ideas? I had a roof repaired at another house and the roofer grooved the brick with a saw and then caulked and inserted the top of the flashing into the groove. Looked to me like it would be near-impossible to leak. Wondered if this might be applicable to the chimney? Perhaps use a concrete-cutting blade and groove all the way around down to the wood base and caulk and flash? Any "miracle" sealants out there that could be applied to the artificial stone and still leave it looking like stone?

Regards,
John

 

[oldognewtrick]

John, first off welcome to House Repair Talk.

Sorry to hear about the problem you are having with your chimney. You basically have 2 options:

1. Continue to put band aids on a problem that will only get worse, sealers and caulking will only mask your issues. There are gaps in the mortar bed and water will find its way in the cracks, behind the stone and get behind any existing flashing you have. Installing new flashing will not solve anything, because you cannot get behind any water barrier on the side of the chimney. New flashing will be a topical application and you need to get to the wood chase.

2. Remove the stone. I know, you don't want to hear this but its the only fix. Remove the stone, install a water barrier such as Weather Watch, install a transition flashing ( which is a Z flashing) to the side of the chimney, lapping the Weather Watch over the top of the Z. Install new stone on the chimney and new shingles and step flashing around the chimney , tucked up under the bottom of the Z. The existing shingles will be destroyed around the chimney during the demo and refit.

I went to a house yesterday, 9 months old , and I'm taking my masonry guy back on Monday to write a estimate for the very same repair you have. I really like the way stacked stone looks, but very few installations are done correctly. Weather Watch is a rubber based, peel and stick type membrane that will seal around nails.

Wish I had better news for you but you will send good dollars after bad if you don't address the underlying cause of your chimney leak.

 

[jlaustin]

John, first off welcome to House Repair Talk ...
Wish I had better news for you but you will send good dollars after bad if you don't address the underlying cause of your chimney leak.

Thanks for the detailed reply! I was afraid that re-doing the chimney's stone was the permanent answer ... if that's what it takes, that's what I'll do! Thanks again,
John

 

[Chatta5]

Oldog/Newtrick is right. We tried the band aid fix on our stacked stone chimney last year. We replaced the shingles, flashing, and thought we stopped the leak. One year later, the water is coming in from somewhere again.

To complicate matters, we have stucco (which is cracking) above the stacked stone. The stacked stone is the portion that touches the roof ... which leaves me with a question. Can we simply remove the foot or so of stacked stone right above the roof line, get to the plywood chase, and then apply the z flashing and Weather Watch? The chimmey could be leaking from anywhere above the roof line, but can we simply seal the area of the roof to keep it from entering? Our chimney is for decoration only ... we have a ventless fireplace. One contractor recommended even tearing the chimney down!

The water is leaking through the drywall of our living room ceiling (no attic above). Since the drywall has to be replaced, I wonder if we could so anything from inside the house? Thanks in advance for your advice.

 

[joecaption]

The way I would have built that chimmney would have been to frame it sheath it with Advantec subflooring (holds up much better to water) wrapped the whole thing with tap paper then with storm and ice shield, 24" up the chimmney, 24" on the roof, laid the shingles using step flashing, counter flashing of black coil stock or better yet copper, installed 1 X 6" vinyl lumber around the base, Z mould on top of that then the stone. Once the stones laid there needs to be a chimmney cap at the top that would be one piece and is bent so it has at least one inch down over the sides.
Doing all this I'd be sure 100% it's not going to leak.
If you Google "flashing a stone chimmney" a lot of sites come up with pictures.

 

[RichSchmidt41]

Oldog/Newtrick is right. We tried the band aid fix on our stacked stone chimney last year. We replaced the shingles, flashing, and thought we stopped the leak. One year later, the water is coming in from somewhere again.

To complicate matters, we have stucco (which is cracking) above the stacked stone. The stacked stone is the portion that touches the roof ... which leaves me with a question. Can we simply remove the foot or so of stacked stone right above the roof line, get to the plywood chase, and then apply the z flashing and Weather Watch? The chimmey could be leaking from anywhere above the roof line, but can we simply seal the area of the roof to keep it from entering? Our chimney is for decoration only ... we have a ventless fireplace. One contractor recommended even tearing the chimney down!

The water is leaking through the drywall of our living room ceiling (no attic above). Since the drywall has to be replaced, I wonder if we could so anything from inside the house? Thanks in advance for your advice.

Some pictures of this problem would help me give you some ideas.

Richard Schmidt
Snow White Roofers 1957-2005
New Orleans, LA

 

[GuardianChimney]

2. Remove the stone. I know, you don't want to hear this but its the only fix. Remove the stone, install a water barrier such as Weather Watch, install a transition flashing ( which is a Z flashing) to the side of the chimney, lapping the Weather Watch over the top of the Z. Install new stone on the chimney and new shingles and step flashing around the chimney , tucked up under the bottom of the Z. The existing shingles will be destroyed around the chimney during the demo and refit.

Agreed. I've been in the chimney business for years and this is what you're going to have to do. If you keep putting band aids on the problem, you'll end up spending more than just putting barrier.