# Sealing Chimney Block to Asphalt



## hdavis (Feb 14, 2012)

This is an unsual one. There's a cement block chimney on a building's exterior. The chimney actually goes below grade through an asphalt parking area, and the flue comes out into the basement below grade. The chimney was replaced this summer from just below grade.

Here's the problem: we just had a quick thaw, and about 200 gallons of water ended up in the basement by traveling down the flue, through the furnace, and out onto the floor. Examination of the base of the chimney shows an unsealed 1/4 - 1/2" gap between the chimney block and the asphalt. This appears to be the entry point. Ice build up from earlier storms had resulted in reverse grading, directing melt water back toward the chimney base.

Any suggestions on how to seal this, keeping in mind it's below 20 F here? Currently, the block is completely uncoated. Any other detailing areas to look at?

Thanks, I'll check in later.


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## JBM (Mar 31, 2011)

Rip up the driveway and put in a drain. Stucco the chimney with something like Silpro or Umaco or it will fall apart in less then 10-15 years I would guess. 

Or I guess you could put some sort of wiz bang caulking in between the pavement and chimney?


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## 2low4nh (Dec 12, 2010)

caulking and maybe through some little rocks in there too. I second the coating over it. those block can fail in a few years in our climate.


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## FrankSmith (Feb 21, 2013)

Pictures please. Is this a call back for you?


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## hdavis (Feb 14, 2012)

FrankSmith said:


> Pictures please. Is this a call back for you?


I'll see about getting some - I've been so busy hauling wet stuff out I haven't done much else. This isn't a call back for me - the mason who did it isn't returning calls and it's my GF's place. The next ice storm is supposed to be on Saturday, so whatever gets done has to happen pretty soon.


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## hdavis (Feb 14, 2012)

JBM said:


> Rip up the driveway and put in a drain. Stucco the chimney with something like Silpro or Umaco or it will fall apart in less then 10-15 years I would guess.
> 
> Or I guess you could put some sort of wiz bang caulking in between the pavement and chimney?


The owner knows they have to get a coating on it - the sooner the better. They used the same stucco guy I did - he died last year. I'm leaving that as their problem, I'm just helping get a fix. Permanent is best, but getting through the winter with a temporary solution and getting a permanent fix in the spring may be what happens.


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## JBM (Mar 31, 2011)

Well you have to caulk the seam with something. I would put sand bags down around it too


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## Tinstaafl (Jan 6, 2008)

hdavis said:


> Ice build up from earlier storms had resulted in reverse grading, directing melt water back toward the chimney base.


Sounds like that's the crux of the problem. While you might slow it down with a chewing gum fix, the real solution is going to be whatever it takes to keep water away from that area in the first place.

I see ice chipper patrol in your near future. :sad:


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## Tom M (Jan 3, 2007)

I have been using spray foam a lot more often these days, even as a caulking backer. Unfinished block with reverse grading is going to be a problem no matter what though.


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## hdavis (Feb 14, 2012)

Tinstaafl said:


> Sounds like that's the crux of the problem. While you might slow it down with a chewing gum fix, the real solution is going to be whatever it takes to keep water away from that area in the first place.
> 
> I see ice chipper patrol in your near future. :sad:


About all I can do long term is mound it up around and asphalt / seal around at a higher level and maybe install a drain. Right now, the flue pipe is acting as the drain

I'll have to look it over Saturday when it rains again to see what the water is doing out to the street. I'm not convinced chipping a channel out to the street will fix it, but I'll give it a try and see what happens, I just have to remember to bring a mattock with me. In the mean time, goo and sand bags may have to suffice.:blink:


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## hdavis (Feb 14, 2012)

No matter what, this won't be right. I don't think there is a realistic way I can get the prep done for the caulk, so I'll caulk it, but I'll have to pull it back out in the spring, when I can actually do this right.

I'm really liking the sandbag suggestion. If I put plastic down on the ground and up the sides, I can put sandbags on top to hold it in place and then put more sand, more plastic...


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## Tom M (Jan 3, 2007)

Your smart enough to come up with something. I can quite vision this. Hollow block would hold water and weep but how its getting into a flue is confusing me.


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## hdavis (Feb 14, 2012)

Tom M said:


> Your smart enough to come up with something. I can quite vision this. Hollow block would hold water and weep but how its getting into a flue is confusing me.


That's another piece of the puzzle. It has to be getting to the inside of the concrete blocks from the outside. I'm thinking this will have to be dug out in the spring and looked over. It has to be going down in the open seam, then finding a way to the inside of the block, then it runs down the flue, through the furnace, and onto the floor.

If it wasn't so cold outside, I'd take the flue pipe out and run a hose on the seam to see where it seems to be coming in.


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## CarpenterSFO (Dec 12, 2012)

Trowel a thick 3" band of sikaflex down then build a 3 or 4" high and wide curb with a bag of quikrete chamfered or not, to keep the puddle away. And chip a channel in the asphalt to direct it away. Correct the grade in the spring.


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## hdavis (Feb 14, 2012)

I found another problem. When this was rebuilt, the ends of the gutter where the chimney is were sealed by gooing to the chimney with silicone - no end caps. One gutter (PVC) has pulled away from the silicone lump. I'm liking this less as I go. I'll have to hunt around for some end caps, or fabricate some.


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## CarpenterSFO (Dec 12, 2012)

hdavis said:


> I found another problem. When this was rebuilt, the ends of the gutter where the chimney is were sealed by gooing to the chimney with silicone - no end caps. One gutter (PVC) has pulled away from the silicone lump. I'm liking this less as I go. I'll have to hunt around for some end caps, or fabricate some.


That could pour a lot of water straight down the chimney, and seeping into it if the CMU isn't sealed or the joints aren't solid.


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## hdavis (Feb 14, 2012)

That's what I was thinking. I have two more loads of wet boxes and ruined inventory to take to the dump, then I'm on the fix. 

I set up a dehumidifier as soon as most of the water was out, a conventional HEPA unit that's class 100 capable, and an electrostatic HEPA that's class 200 capable (actually measured, so I know what these particular units actually do). The electrostatic one is basically providing an air curtain to prevent anything from getting up stairs through the cellar way to the retail space. It takes air from floor level and shoots it up to the ceiling, where it curls back down and gets brought back into the filter unit. No smell, no noticeable mold growth. 

Having a little extra time to get it dried out is the only good thing about the cold weather.


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## JBM (Mar 31, 2011)

You shoudl have just called servepro, I dont think their services effect the deductable.


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## dom-mas (Nov 26, 2011)

This weekend is supposed to be fairly warm, maybe use some coldpack around the base to build up the grade


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## hdavis (Feb 14, 2012)

JBM said:


> You shoudl have just called servepro, I dont think their services effect the deductable.


No chance at all. I've seen them in inaction. Also, there will be no claim. The way it works is as soon as you notify insurance there will be a claim, you're pretty much hands off. There's a delay while insurance contacts whatever company. The company guys show up, then they dog it while mold starts growing. Everyone waits for the adjuster, since that has to happen before the real work begins. Show me an adjuster that can correctly value inventory - that is a big mess and a good place to get into an argument with the insurance company, eating up a lot of time. All the affected boxed inventory goes to the dump or wherever. Meanwhile, your customers go to competitors, and most won't come back. 

So you're stuck being closed for however many days, with extra time down if dogging it leads to a tear out, and a few weeks getting inventory back in. Now all you have to do is get customers to come back. 

Better to keep the business open, throw out the boxes and affected inventory, keep the unaffected inventory, and keep your customers. Kinda sux, but in this case, less money is lost by going this route.


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