Sealing Top Of Chimney

 
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Old 02-22-2011, 08:30 PM   #1
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Sealing Top Of Chimney


I have a client's chimney that is causing eflourescent inside the attic. I looked at the top and it looks like it leaking in the cap part. I don't think it is coming from the flue itself but just to make sure I am going to install some caps on the flues. I think it is the mortar cap.

Any ideas? Ideas on how to seal it?
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Old 02-22-2011, 08:36 PM   #2
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Re: Sealing Top Of Chimney


No amount of sealer would stop water from getting in there.

That calls for partial tear down, rebuild, and pour a new cap.

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Old 02-22-2011, 08:44 PM   #3
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Re: Sealing Top Of Chimney


Can you just remove the old cap and repour?
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Old 02-22-2011, 08:45 PM   #4
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Re: Sealing Top Of Chimney


I guess another way would be to make one big metal cap. The problem is that it is crooked on one side.
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Old 02-22-2011, 08:54 PM   #5
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Re: Sealing Top Of Chimney


From what I can see you have to tear down at least 6 courses and rebuild. Pour new cap using sand with a portland type 2 a little strong and make sure the finish is smooth and slick. Repoint the rest of the chimney and if you want to go the distance use Chemstop WB HD on the entire chimney exposed after a few days of cure on the repairs to give it a good water repellent (its not a sealer, it lets the brick still breathe).
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Old 02-22-2011, 08:56 PM   #6
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Re: Sealing Top Of Chimney


You might get away with removing the old cap, which usually is adhered to the brick pretty well, so you'll be replacing some regardless. Then you can grind and tuckpoint the rest.

I imagine though, that many of those brick are rotted, judging by the moss growin on em. If it were my job, I would push for a partial tear down and rebuild, pour a new cap, and tuckpoint the remaining.
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Old 02-22-2011, 08:58 PM   #7
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Re: Sealing Top Of Chimney


Tuckpoint the top section of mortar joints. Then cut out old cap, pour a new cement cap. Very easy repair
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Old 02-22-2011, 08:59 PM   #8
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Re: Sealing Top Of Chimney


I've got to agree. Even if the tiles are capped it will still take in some water, IMHO. While it is true the tiles should have a rain cap to keep water out the water causing your efflorescence probably is leaking in from the cap and bricks.

I feel like many larger chimneys are subject to greater expansion & contraction problems.

You can see the algae build up in the second photo. There may be microcracking in a large number of those bricks and at the brick/ concrete cap interface. The cure is a may be a fair amount of grinding and pointing. Visit the chimney right after a rain and the hairline cracks will be more visible. (or provide your own water)

I'd try to sell a power wash, grind and re-pointing of the needed brick, a treatment of the cap and possibly a silicone treatment.

The cap would involve plugging the tile, repairing the cracks and maybe a light coat over the entire surface to unify the appearance.

They get their leaks fixed and a better looking chimney.

If you can sell the extra work it will save you having to come back several times running down leaks when the initial repair doesn't do what was desired.

That's just my take on it based on 2 pictures, you have a better view than I do....

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Old 02-22-2011, 09:18 PM   #9
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Re: Sealing Top Of Chimney


I would want it torn down to where the stepped brick starts, and built back up straight. That stupid step design is probably taking on more water than the cap itself.
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Old 02-22-2011, 09:56 PM   #10
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Re: Sealing Top Of Chimney


Powerwash, grind and re-point, then cap that sucker with a real poured crown (4" concrete with #5 rebar cage) form a 2" overhang and provide drip relief or, just remove the existing crown and order a stainless chase cover. Most chimney liner supply companies will make these to your specifications.

As far as the flue covers - put them on! Water regularly enters the flue and will seep through open terracotta joints and offsets. I would recommend a multi flue knock down kit ,stainless off course, custom ordered to fit with a 6" clearance from flue.

When you done, seal it up with a quality, breathable sealer
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Old 02-22-2011, 10:33 PM   #11
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Re: Sealing Top Of Chimney


Your crown needs replacing..

But if you look at the one that is there now you can see that it is not that old.

Those cracks in the morter are from it setting too quick.

On hot days if you lay your crown without moistening it it will get cracked and crazed to the point of it needing to be redone.

I had a guy that would work the crown and before he left he would spray some WD 40 on it to keep it from cracking.

Bag of type S, 2 to 1 and work it.

click for caps

http://www.fireplacemall.com/Chimney...iple_flue.html
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Old 02-23-2011, 01:40 AM   #12
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Re: Sealing Top Of Chimney


Yeah, if the budget allows tear out the cap too....

It looked to me as though this may have been repointed before; yes or no? If it has been and if the whole thing is riddled with cracks it might be worth just taking it down to the flashing.

Did one last year that instead of rebuilding it, I just lowered the whole thing about 12 courses and then capped the entire thing since it was no longer in service. It was a historic building and they still wanted it to look like it was functional. They didn't want to spend the money to take it back up to original height.

You guys ever get to the point that when you take em down it is better to just roof over them? Lots of them are no longer truly functional and end up losing a lot of heat up them.

It usually isn't quite worth it by the time you end up doing insulation, un-flashing, and um.....de cricketizing, and re-shingling but I'd venture that the day is coming.......

LOL; the bill went up from just filling the flue pipes, eh?

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Old 02-23-2011, 04:53 AM   #13
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Re: Sealing Top Of Chimney


There is an alternative depending on the budget this client has. It is basically encapsulating the crown with a rubberized polymer which will flex and keep the rain out.

Two products are available for this: Crown Seal and PMP. PM me for more info if interested.

Make sure your follow the specs as Crown Seal is very temperamental.

Condensation in the attic could likely be from the furnace or hot water flue as well. Any repair to the crown or exposed chimney will not solve a condensation problem... just an FYI.
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Old 02-23-2011, 05:22 AM   #14
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Re: Sealing Top Of Chimney


This is a problem I've been solving for 30 years.

If the top courses of brick are still sound, a full chimney cover will stop the water entrance and further damage. The roof portion of the cover needs to be larger than the chimney top and fairly low profile to reduce wind blown infiltration. The tops of the corbels should be sealed with an NP1/Geocel 3300 type caulk after the brick is cleaned and tuck pointed if necessary.

We've used Geocel 2315 with good success to seal the existing crown if it's basically sound with some cracks.

If anything is loose, then it needs to be rebuilt. Then add the full cover to keep it from happening again.

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Old 02-23-2011, 10:35 AM   #15
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Re: Sealing Top Of Chimney


I've seen plenty of those mortar washes/crowns in my career, and regardless of what the material is, they're all fundamentally wrong IMO. Optimally, you need some form of cap, whether it's concrete, steel, aluminum, etc..., that overhangs beyond the corbelled brick a min. 2" and has a drip edge under it if you want that to last long term. If you want to retain the corbelling it has now, I'd recomend putting a small mortar wash over each course of brick that's corbelling back IN. You won't see it from the ground, and it will make those joints far less susceptable to leakage.

Of course, it may be best to remove the top 6 courses or so and just corblel the last few courses out, rather than out then in.
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Old 02-23-2011, 11:27 AM   #16
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Re: Sealing Top Of Chimney


The corbels aren't the problem although the current design isn't really made to last as long as others. The cap/crown is to thin, has heaved in some parts from what I can see in some pictures, is cracked and I bet if you run your hand on it is it grainy as hell. Take off the cap first. If there is lots of loose material inside behind the top bricks and if the bricks at the top loose then tear down till they are solid again. Go easy cause you can loosen good bricks. If you need to rebuild the corbels then go a for a simple yet clean looking design, in 6 courses step out 6 courses down 3/8", 5th course down another 3/8" then step the 4th down 3/8" and build the last 3 on top of that one. This will allow good wear and prevent water run off from sitting on the joints. It'll look a hell of a lot better too.

If they are solid just use a tuck point blade on a saw to eat out the joints that have any openings and/or moss/algae growing. Re point the joints using a good strong mortar mix. Poor the cap 3" thick with a good concrete mix and taper the ends so there is good run off. Arch it so that there is no area for water to sit everything runs away from the flues and has no where to go but off the edge. Also make sure the finish is smooth, this is key to it lasting many, many years and protecting the rest of the chimney. You can even use a hydraulic/waterproof cement compound on top in a thin layer to finish it off nice and strong.

95% positive the leaching and efflorescence and the reason the top courses of brick are holding moisture to allow the moss/mold growth is the cap's porosity+cracks. Depending on the homeowner's budget still offer a SS cap on top either way.

Now many people use caulks for a cheap quick fix. Don't use any type of caulking on the repairs, I don't care what it is even if nasa uses it. It will either separate from heat/water in short time and/or seal up different areas not allowing the bricks/joints to breathe. And if you still think its the best option the take a look at it in 3-5 years...

Don't use "a" water proof sealer. Any sealer on bricks chimneys will not let them breathe properly, holding in moist creating leaks, etc. Chemstop WB HD is a brick water "repellent". Only one and a good one. It doesn't seal, it helps repel water but allows the bricks to breathe.


Just remember, masonry chimneys will last 40+years if repaired/built properly. If bricks can't breathe you will be shortening there life and life of the chimney. Very important. Everyone here has good points here and there but overall Masonry on Masonry, no other way around it. Look around, old masonry built buildings etc are still around for many many years.
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Old 02-23-2011, 01:53 PM   #17
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Re: Sealing Top Of Chimney


If you go for a rebuild I would consider putting a lead tray/through flashing in. If re pointing using weather cut and struck style would help weather proof the joints. I would also put a sand/cement fillet on top of the corbels.
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Old 02-23-2011, 07:12 PM   #18
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Re: Sealing Top Of Chimney


Stu - you know this guy?

Lead pans far are few between over this side of the pond although every masonry chimney should have one. Same goes for bell and spigot flues. The standard here is butt the joints with refractory - never lasts long with the expansion and contraction and leaks soon follow.

Good suggestion!

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Old 02-23-2011, 08:35 PM   #19
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Re: Sealing Top Of Chimney


WOW. Thanks guys for the responses. Talked with my brick mason today. He could only look at the pictures that I had and he agreed that we just need to take the top poured cap off. Repair the top course of brick if need be. Then repour with a new cap with a little rock in it. If needed, he would take down some of the courses.

When I was there everything appeared to be solid except for the cracks in the top. I agree that it looks like it is coming through the mortar top and then going down. The fireplaces are being used. They are side by side but on opposite sides. The last flue is for the furnace in the basement.

The top itself is pretty solid. Can I just install a full metal cap over the whole thing and it would take care of everything? This client has paid for a lot of things over the last year or two because of the contractor that built it. The house was renovated/added about 10 years ago.
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Old 02-23-2011, 11:30 PM   #20
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Re: Sealing Top Of Chimney


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Originally Posted by Mitch M View Post
WOW. Thanks guys for the responses. Talked with my brick mason today. He could only look at the pictures that I had and he agreed that we just need to take the top poured cap off. Repair the top course of brick if need be. Then repour with a new cap with a little rock in it. If needed, he would take down some of the courses.

When I was there everything appeared to be solid except for the cracks in the top. I agree that it looks like it is coming through the mortar top and then going down. The fireplaces are being used. They are side by side but on opposite sides. The last flue is for the furnace in the basement.

The top itself is pretty solid. Can I just install a full metal cap over the whole thing and it would take care of everything? This client has paid for a lot of things over the last year or two because of the contractor that built it. The house was renovated/added about 10 years ago.
Ah finally some input on your customer . Well for what your looking for, repoint those joints that are growing mold, etc at the top. They already hold water/moisture and besides other things getting repaired, the mortar in them will begin to decompose. That's easy/quick work for your mason. Needs a new cap no matter what. But that's easy for him to, still get a smooth finish and arch it outward to produce runoff the sides of it (no standing water) but he should know that. Then just get a SS cap on top and make sure it fits over the cap nice and tight so high winds don't mess with it.

It's not that bad and will save your customer money while having it fixed for the long haul.

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