# Need advice on cinder block (external) chimney repair and waterproofing (New Pics of damage)



## Northeaster1 (Oct 15, 2009)

Hi folks,

We have a 30 year old external cinder block chimney, that has a couple of cracked bricks and some mortar missing from the joints.  It has a stainless liner, for our PE fireplace insert.  Last year, we did replace the top 6 ft of the chimney, and poured a new concrete topcap, as it had the worst # of cracked bricks.  It looks like a previous owner has added mortar to the joints.  This is now loose in most places, and I have chipped away all of the loose stuff.  I can fill in the joints with mortar, and maybe roll / brush on some type of concrete sealer.  

However, I am wondering if there is something better out there.  For example, I watched a youtube video on spray on polyurea - which they sprayed on a cinder block, and it made it very strong - showed them trying to break it with a sledge, and having a lot of trouble.
I could not find any polyurea dealer locally - Nova Scotia, Canada.

Wondered if a mobile truck bed liner company would spray a chimney?  It is a pretty tough, waterproof poly-something type of coating!

Mainly, I want to seal and protect it from getting water in, and freezing, and if it looks better, that's a bonus.

Thoughts??


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## EatenByLimestone (Oct 15, 2009)

Personally I'd just repoint the thing.  If it needs to be done again in 30 years will you still own the house?



Matt


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## Northeaster1 (Oct 15, 2009)

I am considering just repainting it, but would likely have to remortar the seams before painting.  I just wondered if there was something better than regular paint, like epoxy paint / coatings, etc.

As the house has vertical cedar boards, painted white, I could also stap the chimney, and screw n vertical cedar boards, to match the house.  This woudl keep out the weather as well.  
Also could rebrick the outside, using something like those thin bricks, made to be more cosmetic than anything - but would also keep the water out.

Other options?


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## pgmr (Oct 16, 2009)

Check out Quikrete Quikwall.  Not sure if it would work since you mentioned "repainting", but you might want to read up on it.


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## branchburner (Oct 16, 2009)

When sealing a chimney I don't think you want it waterproof - you want it to resist moisture, but still want it to breathe. I'm no expert but that is my understanding. For my brick chimney I used a repellent from a masonry supply house, and for my block chimney that was painted I simply repainted it  - latex was what I was advised.


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## Northeaster1 (Oct 16, 2009)

Thanks for the replies!

I am a bit leary of quick-crete type / plaster / stucco products, as my Dad had his cinder block basemnent walls done iwth something like that, that started to peel off a few years later.  Looks like it is for motarless walls - didn't know you could do brick without mortar!  Since mine has been painted before, it may not stick well.  I will likely use mortar to repair the joints, then paint of waterproof.

RE: latex paint, this was the recommendation of my local hardware store.  And it may be the best option.  I juts thought there must be something better out there, specifically for sealing concrete.  I just sealed my carport concrete floor with concrete sealer, but it is so thin, I don't know how it would work on the vertcial chimney - maye be better with latex paint!

There are lots of products on the net, like epoxycoat, amourcoat, etc.  I just wondered if any of them would provide some strength to the wall as well as sealing it.  Thye don't seem to be available locally anyway!


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## drewboy (Oct 16, 2009)

Thompsons makes a sealer made specifically for masonry, I saw it at Lowe's last week but I didn't have time to check it out further. I have read that regular water sealer (for decks and such) is no good but I am curious as to what makes the masonry sealer so different. I have a moisture issue on one of my block chimneys as well and it actually cracks and pops the corners off in below zero weather so I need to find a solution before the winter. I will follow this thread for more ideas.

  Rob


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## Northeaster1 (Oct 16, 2009)

Rob - It would be nice to hear from someone who knows the difference between norall driveway concrete sealer, and the masonary sealer - if it's not just the same stuff in a different can!

looks like rain this afternoon, so I will have to hold off for a few days on the re-motaring anyway.


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## crazy_dan (Oct 16, 2009)

I would probably look to a product like this http://www.ugl.com/drylokMasonry/masonryWaterproofer/latex.php 
It does state cinder block, and above grade. comes in 4 colors I believe and they used to have both oil and latex.
as so says it is breathable do it will not trap moisture, It sounds to me to be what the doctor ordered after you get the joints fixed.
I See they have an extreme formula too so check it out.


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## Hogwildz (Oct 16, 2009)

Re-point, and put some cultured stone on there .


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## Northeaster1 (Oct 16, 2009)

Well, after chipping away most of the loose mortar, I see that 3 cinder blocks have more than hairline cracks in them.  They are actually bowed out a bit, and I could easily bust up the faces with a hammer.

I called a couple of local masons, but they are too busy this time of year!  My fault for waiting.  Will do the job myself.  Should I be looking at trying to replace the 3 worst bricks, or juts bust the loose stuff off of the cracked faces, and use mortar, or a patching compound to fill in the damaged sections.


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## Hogwildz (Oct 16, 2009)

None of the joints are staggered?
If it feels solid, just knock the loose off and parge it. Otherwise get to replacing.
Unstaggered joints looks wrong to me. Thats a weakness in itself.


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## Northeaster1 (Oct 16, 2009)

I agree with you on the unstaggered joints!  But, I didn't build it.  We knocked off the top 6 ft last year, (above roof level) as there were many cracked bricks and loose mortar.  We bult it back up, but did stagger the joints.  Other than the bricks shown, and a couple of others with hairline cracks, the chimney is solid.  It is a double chimney, as well, so the extra width likely adds some strength.

I will probably start with the worst block, and see how much I need to knock off, before hitting something solid, on which I can buiold it back up.  If it's not too bad, I will follow your advice and parge it back up.  
What type of compound is used for this, regular, mortar, patching stuff, ???


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## Hogwildz (Oct 16, 2009)

Northeaster1 said:
			
		

> I agree with you on the unstaggered joints!  But, I didn't build it.  We knocked off the top 6 ft last year, (above roof level) as there were many cracked bricks and loose mortar.  We bult it back up, but did stagger the joints.  Other than the bricks shown, and a couple of others with hairline cracks, the chimney is solid.  It is a double chimney, as well, so the extra width likely adds some strength.
> 
> I will probably start with the worst block, and see how much I need to knock off, before hitting something solid, on which I can buiold it back up.  If it's not too bad, I will follow your advice and parge it back up.
> What type of compound is used for this, regular, mortar, patching stuff, ???



You prolly have a few options.
I am not a professional mason, you should do some deep research.
That said, I myself would prolly use Quickrete Masons Mix, 
or The Fastset DOT mix is good enough for Sept. of Transportation bridge repairs  & strong etc.,
there is also Fastset Repair Mortar. And last but not least is Heavy Duty Masonry Coating.
I think the mason mix will do just fine. its also good for tuck pointing.
Keep in mind if you parge, you need the joints underneath to be tight & stable, or else the parging will only crack with the joints if they crack.
You could also attach wire mesh to hep reinforce the parging. Or even stucco or stone veneer over the mesh to make a nice finish.
Take your time, research, then research some more. And it don't hurt to ask any mason friends.
If parging, it is suggested to also use a bonding agent to help assure a good bond.
I used mason mix for the cultured stone I am installing, and the nice part is, add water & mix, no mixing sand & portland etc etc.
Stuff is tough too.


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## Yagminas Masonry and Wood-heat (Oct 16, 2009)

I use type "s" for laying block and Bomix parge mix for parging. I also use Thompson's in a sprayer and it seems to work well. The best thing I do for chimneys is a metal cap with a drip edge of at least 1-1/2"....

I often see stack bonds on warehouses and commercial buildings. Sometimes it's a bit tricky to remove one without the one on top sliding down. Have some wooden wedges handy just in case. Another tip- plug the holes in the new block with roxul insulation. That way when you slick in the top joint it doesn't fall down in the cavity and you can slick it in to the hidden joint in the back.


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## Northeaster1 (Oct 17, 2009)

Hog - thanks for the advice.  Are you resurfacing a chimney with cultured stone?  If so, what was there before?  And how much is the stone costing you, per sq ft?

I may just repair and paint now.  Or, I may repair, and consider covering over the cinder blocks with cedar, to match the house, or some type of facing brick or cultured stone.  What would have to go on to the cinder blocks, in order to install cultured stone? ie vapour barrier, etc..  Or can I juts mortar up the stone, right against the cinder block?


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## Burd (Oct 17, 2009)

Do you have to wire the chiminey if you reface it  Or are you going right over the block.
Please fix them blocks before you do any thing that crack is a sign of weekness in the strucsure


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## Northeaster1 (Oct 17, 2009)

Yagnminas - so you think I should try and completey remove the bad blocks, and replace with new ones - rather than juts knocking off the loose parts, and "patching" the faces?  Since there are 3 bad ones on top of each other, and just above that is one more block, and then the new 6ft scetion we replaced on top last year - since we staggered it, this should prevent anything above from falling!

Do you think it would be Ok to carefully knock out 3 or 4 blocks, on top of each other, without affecting the structure too much.



Burd -  not really sure what is needed, if I decide to cover the cinder blocks.  That's why I am asking you guys here.  Would a person normally attach mesh, then run a new row of stone, using the mortar to tie into the mesh?  

What are my options.  I don't want to do a half assed job, but don't want to tear down the whole chimney, for 3 cracked blocks either.


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## Hogwildz (Oct 17, 2009)

Northeaster1 said:
			
		

> Hog - thanks for the advice.  Are you resurfacing a chimney with cultured stone?  If so, what was there before?  And how much is the stone costing you, per sq ft?
> 
> I may just repair and paint now.  Or, I may repair, and consider covering over the cinder blocks with cedar, to match the house, or some type of facing brick or cultured stone.  What would have to go on to the cinder blocks, in order to install cultured stone? ie vapour barrier, etc..  Or can I juts mortar up the stone, right against the cinder block?



I am actually doing the cultured stone inside the house at the moment. But plan on installing it on the block chimney also.
If the block is unpainted, you can install the stone directly to the block. My block is bare block.  I think it was about $6.10 sf when I bought 4 pallets last year. You can buy smaller boxes & corner pcs at same price as pallets sf price I believe. I suggest against putting cedar against the chimney, pretty sure that will fail code, and could be a fire hazrd in the event of chimney fire with high temps. If you paint it for now. You will either have to sandblast the paint off, or install wire mesh to the block if you decide to install the cultured stone later on. No vapor barrier when installing the stone to cement, stone or stucco surface.


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## Northeaster1 (Oct 17, 2009)

The reason that I had thought about putting cedar over it, was that a neighbor just covered over his old chimney with clapboards, to match the siding on his house.  Of course, I would want it to be up to code, so I would have to see if it is allowed, and if so,  how it needs t o be installed.  

The chimney has double 12x12 clay liners, in one of which we have a full stainless liner (all solid execpt for flex to connect the insert).  Since the heat is in the stainless liner, which is inside a clay liner, which is inside the cinder blocks, I don't see how cedar - strapped / screwed to the outside of the blocks - would be a fire hazard.  But, I would have to check on the code.  Not leaning this way anyway.

I don't want to sound stupid, but I don't know if the chimney was painted a long time ago or if it is unfinished.  There is no peeling paint!  But it looks a more grey, and more shiny that unfinished blocks, or is it just me?  Maybe it was waterproofed years ago.  The previous owner was not big on reapirs and maintenance, so I doubt if it was ever treated.

When i called a local brick manufacturer, to ask about cultured stone, he didn't ecnourage their use outside, and mentioned having to put some tyoe of vapour barrier ,etc.  I will have to check further.

Has anyone refinished their old block or brick chimney with some type of facer brick or stone?  What steps were used?


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## Hogwildz (Oct 17, 2009)

Northeaster1 said:
			
		

> The reason that I had thought about putting cedar over it, was that a neighbor just covered over his old chimney with clapboards, to match the siding on his house.  Of course, I would want it to be up to code, so I would have to see if it is allowed, and if so,  how it needs t o be installed.
> 
> The chimney has double 12x12 clay liners, in one of which we have a full stainless liner (all solid execpt for flex to connect the insert).  Since the heat is in the stainless liner, which is inside a clay liner, which is inside the cinder blocks, I don't see how cedar - strapped / screwed to the outside of the blocks - would be a fire hazard.  But, I would have to check on the code.  Not leaning this way anyway.
> 
> ...



Your chimney may have been sprayed with some kind of waterproofing, I don't know. My block is not shiny at all.
You could always attach metal mesh and then install the stone veneer. If done properly, you should have no problems.
The key with stone veneer, is to make sure you get 100% coverage of the mortar on the back of the stone and to the surface you are attaching it to.
This leaves no space for water to get behind, freeze & pop it lose. I would think if your using that chimney during the winter months, especially 24/7 burning, it will throw off a small amount of heat at the least and keep freezing from even happening. But done right, this should not even be an issue. You also need to flash it top & bottom properly, again to keep water outside where it belongs.
I plan on doing mine, prolly direct to the block, with proper wall/base flashing at the bottom and I will make a new cap to cover the entire old cement cap. I am thinking copper as it would look real nice with the stone, and would also last longer than me. As someone already stated, a good drip edge on the top cap helps keep the water out and away. But, m,y project is a few down on the list, right now gotta get the inside done first.
Per the directions for the stone I am using, vapor barrier is needed only when installing against a substrate other than concrete, block, stucco etc.


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## wellbuilt home (Oct 17, 2009)

I  dont think i would worry about 3 cracked blocks . Unless the area is free standing . 
 You can just use a 4" grinder and a diamond  wheel and cut the block 1/2 " in along the crack  and point up the area like it is natural joint . 

If you have alot of joints to fix they sell a 3/8 grinder  wheel that will clean the joints out  so you can add new mortar . 
 Cinder block absorbs water and should be parge with a  1/2" of cement ( Portland/ sand mix  with stay tight additive). 
 after its parge you can paint it.      John


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## Northeaster1 (Oct 17, 2009)

John - thanks for the cutting wheel idea.  I have a couple that have hairline cracks, and that will likely be the way that I repair them - just cut in, and make a new seam.  But, the 3 worst bricks are not just cracked, the face of them are delamintated and loose, for a few inches on either side of the original cracks.  I would like to bust out anything loose, and then fill / repair with something,

When you say to parge the blocks with 1/2" portand mix, do you mean to cover the whole chimney, so that it would look sorta like stucco?   I was worried about soing something like that, as mentioned - my Dad had his cinder block basemnet covered with something years ago, and it started to peel / crack off only a few years later.  Real mess. 

After looking again, it does look like the blocks ahve had grey paint put on them, years ago.  Hadn't thought it was paint, as there is no peeling, but on 3nd look, I woudl say that it is.  Since it has been painted, woudl that affect whether I parge it or not - would portand mix still stick to it?


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## Hogwildz (Oct 18, 2009)

Northeaster1 said:
			
		

> John - thanks for the cutting wheel idea.  I have a couple that have hairline cracks, and that will likely be the way that I repair them - just cut in, and make a new seam.  But, the 3 worst bricks are not just cracked, the face of them are delamintated and loose, for a few inches on either side of the original cracks.  I would like to bust out anything loose, and then fill / repair with something,
> 
> When you say to parge the blocks with 1/2" portand mix, do you mean to cover the whole chimney, so that it would look sorta like stucco?   I was worried about soing something like that, as mentioned - my Dad had his cinder block basemnet covered with something years ago, and it started to peel / crack off only a few years later.  Real mess.
> 
> After looking again, it does look like the blocks ahve had grey paint put on them, years ago.  Hadn't thought it was paint, as there is no peeling, but on 3nd look, I woudl say that it is.  Since it has been painted, woudl that affect whether I parge it or not - would portand mix still stick to it?



Since it is painted, whether you parge it, put stone veneer on it, whatever you do, you will have to put wire mesh on then parge/stone whatever you decide. Or sandblast the paint off. Wire mesh is easier IMO.
Get yourself some MAson Mix, its pre mixed, add water and no mixing portland & sand etc. It is a type S I believe. Just came in from putting more cultured stone on the back of my chimney, which is now in my new bedroom I am working on. I boxed it off, dura rock & metal lathe, and stone baby, lots o stone(cultured that is).


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