Chimney cracks pictures added

[cyclone]

I just noticed today that my clay flue sticking out of the masonary chimney and prefab chimney cap have a crack. This chimney was built this year.



Does this happen, anything to be concerned about?

Anything I should do about the cracks?

 

[Hogwildz]

Post a pic.

 

[cyclone]

I'll try to get some pics.

It is where the flu comes out the top of the chimney. The crack runs down to the top of the chimney to the pre fab concrete chimney cap where there also is a crack. I hope this is not a problem and wondering what caused this.

Heat???

Driving around I do notice alot of flues coming out of the chimneys damaged..

 

[dvellone]

You see a lot of damaged chimneys because, unfortunately, a lot have been built incorrectly.

Have you used this chimney yet this season? - you mentioned that the chimney was built this year.

Take a look if you can at the prefab cap/flue tile joint. Did they join the two with mortar?

Most importantly, any insured, legitimate contractor should guarantee their work for one year. (Did you get an insurance certificate?)

Ask them if they mortared the entire length of flue tile to the outer shell, or if they left a clean space between the two. If they in fact mortared the two together you're unfortunately in the same boat as the homes with damaged chimneys that you see. If they only joined the cap and top tile it can be easily repaired. Either way, if this a newly built chimney you need to get after them letting them know that it's their responsibility to correct any problems relating to their work. There is really no reason for damage like this on a new chimney - or a properly built old chimney for that matter.

 

[struggle]

If there is a crack in the clay tile liner then cold air will mix with the hot combustion air of the stove and it will create a perfect storm for a chimney fire. Why do I know this? Because my liner was cracked at the wall thimble and I had a chimney fire.

My fix was to put a flex liner in the chimney, but my chimney was built in 1984 not last year. I would be very concerned if it is cracked at the stove connection area. I tried cementing the cracks that I could reach etc but there is so much you can never see of the chimney itself.

Call the contractor and go from there.

 

[woodconvert]

I'll try to get some pics.

It is where the flu comes out the top of the chimney. The crack runs down to the top of the chimney to the pre fab concrete chimney cap where there also is a crack. I hope this is not a problem and wondering what caused this.

Heat???

Driving around I do notice alot of flues coming out of the chimneys damaged..

My guess is that water got between the flue and the cap and when it freezes and expands it breaks the tile/cap. It's no concern for the operation of your stove but I would get up there and seal it so no further water problems or cracks evolve.

 

[dvellone]

I'll try to get some pics.

It is where the flu comes out the top of the chimney. The crack runs down to the top of the chimney to the pre fab concrete chimney cap where there also is a crack. I hope this is not a problem and wondering what caused this.

Heat???

Driving around I do notice alot of flues coming out of the chimneys damaged..

My guess is that water got between the flue and the cap and when it freezes and expands it breaks the tile/cap. It's no concern for the operation of your stove but I would get up there and seal it so no further water problems or cracks evolve.

He mentions that the chimney was built this year. Seems unlikely that freezing has played a part at this point unless he's at a high elevation in NE Pennsylvania, and they've experienced a sustained freeze. An overnight freeze cycle wouldn't likely be enough to break the cap.

 

[cyclone]

Pictures added of chimney

Second picture you can see the hair line crack running down the flu....

 

[Hogwildz]

Are the cap screws by chance tightened a lil too tight? Is that hairline crack right at that cap mounting screw?
Can you pull the cap and see how far it cracked down? If its limited to the exterior part of the clay, It might be ok, just get rid of that one cap screw in that spot. Looks like a lot of clay coming out the top of that chimney. Maybe cut it down some so just 3" or so are coming out the top. Then try some high temp silicone and check periodically to see if it grows any longer.
Might have to dismantle the top clay tile and such down to the next and rebuild. Hopefully a mason will chime in.

 

[woodconvert]

I'll try to get some pics.

It is where the flu comes out the top of the chimney. The crack runs down to the top of the chimney to the pre fab concrete chimney cap where there also is a crack. I hope this is not a problem and wondering what caused this.

Heat???

Driving around I do notice alot of flues coming out of the chimneys damaged..

My guess is that water got between the flue and the cap and when it freezes and expands it breaks the tile/cap. It's no concern for the operation of your stove but I would get up there and seal it so no further water problems or cracks evolve.

He mentions that the chimney was built this year. Seems unlikely that freezing has played a part at this point unless he's at a high elevation in NE Pennsylvania, and they've experienced a sustained freeze. An overnight freeze cycle wouldn't likely be enough to break the cap.

Dunno the what the weather there has been but one night of freezing is more than enough...our roads suffere the same consequences overnight. It's unbelievable. Whatever the cause, then, you now have to seal the crack(s) or it will be much worse by spring.

 

[dvellone]

It looks like the tile is mortared to the cap if I'm seeing it correctly. If so and if you've been using the chimney this is likely to be a cause of the cracking.

The tile needs to separate from the block for it's entire length- a complete airspace free of any mortar. The reason for this is because the tile will"grow" as it increases in temperature quite a bit more than the block. Clay tile and the outer shell will expand and contract at different rates causing exactly the kind of cracking you're seeing. Once the crack forms it will allow a substantial amount of water to enter which then, once temperatures plummet, will cause more severe spalling.

There are a lot of folks out there that think, mistakenly, that the tile needs to be mortared to the outer unit when in fact it is free standing and the space is instead filled with perlite, vermiculite or left as a void.

If your masons didn't construct your chimney in this manner now is the time to seek reparation when the chimney is new and their work still guaranteed. This problem will only get worse and silicone, parging, or other surface treatments will only be a temporary fix at best.
It would be best to talk to them and find out how they constructed this chimney to confirm the cause of the crack.
I am a Stone Mason having run my own business for 16 years following trade standards.

 

[cyclone]

The pre fab chimney cap is probably mortered to the flu. The construction as I observed the person doing this from the ground up would lay some blocks then place the flu in when needed. t All the flu's have the space between them and the chimney block until I think as you mentioned at the top where the last block was placed and flu with the pre fab chimney cap being put on over the flu and resting on the last chimney block. Sure he pit the morter on the chimney block placed the pre fab chimney block on top leveled and filled the rest in with mortar.

Can this be fixed easily???

What needs to be done??

 

[dvellone]

That's good news that the final tile is the only problem. You essentially want to remove the mortar line that is bonding the tile to the cap. That void gets filled with a quality sealant. A large angle grinder with a diamond blade will cut the mortar easily, but you have to have enough depth of cut to make certain that all the bond is removed. The tile should break free of it's bond to the tile below and you can lift it out for replacement. Being the top tile it's really not much worth trying to repair the crack. The repair won't match the strength of undamaged tile and it is the most exposed tile weather-wise. There are some epoxy sealants on the market that will neatly repair the crack in the cap. They tend to work a bit better than parging, lasting longer and easy to use.

You really shouldn't have to go up there to do this work though. You spent a good buck having a masonry chimney built and the builders need to make it right.

 

[webbie]

That tile should not stick out of the top more than 6 inches - maybe less. This is actually part of the code, but for good reason.
Replace it as mentioned above, but with a shorter one and with a flexible joint.

Flue tiles suck - there is really no reason - except powerful lobbying interests - for them to be used in modern construction. I have seen MANY of them cracked in the pile at the masonry yard - if not cracked there, they are almost always cracked as soon as they hit weather and any mechanical forces.

 

[dvellone]

That tile should not stick out of the top more than 6 inches - maybe less. This is actually part of the code, but for good reason.
Replace it as mentioned above, but with a shorter one and with a flexible joint.

Flue tiles suck - there is really no reason - except powerful lobbying interests - for them to be used in modern construction. I have seen MANY of them cracked in the pile at the masonry yard - if not cracked there, they are almost always cracked as soon as they hit weather and any mechanical forces.

I have to take issue with your opinion that they suck. They are certainly susceptible to breakage if mishandled or incorrectly installed, but when constructed properly a masonry chimney is a thing of beauty and functionality, and long-lived. I see properly built chimneys around here that have been in use for many years that are in great shape in and out. . When the masonry structure is built in the home - where it should be- and the flue tile is insulated, the mortar all properly laid and cured, it is a hard thing to rival. Like anything, they are as good as the person constructing them. Stainless insulated prefab has the advantage of being fabricated under a great amount of control to exact specifications. The average guy wanting to make a buck off someone else, though maybe able to install it, thankfully can't construct it. Masonry relies on Craftsmen who are in dwindling supply these days, and thanks to the world of prefab ( which I do find value in) are becoming increasingly difficult to find. And just how long is the expected lifespan of a stainless insulated flue anyway?
Sorry had to "vent". This all from a Stone Traditionalist watching all the "stick-on stone" fireplaces going up.

 

[webbie]

I guess I should be more clear.....

I personally love masonry chimney, but given modern technology I think square clay flue tiles are not up to the task....at least in colder freeze thaw climates. If I was to build a masonry chimney, I would look at either round flue tiles (stronger, better draft) or an isokern type:
(broken link removed to http://www.isokern.net/pages/chim/dmsys.htm)

Or even a masonry chimney with a poured in place liner.....

But when it comes to thin clay square and rectangle flue tiles - I am not a fan. I have had them fall apart when I try to cut them, etc. etc. and they are just not up to the task IMHO....

It's interesting because I grew up in an area where homes were built right, and many homes used round flue tile surrounded by vermiculite and other insulation which allowed expansion and kept them warmer, etc. - but, as you mention, the art was lost - mostly from post war (WWII) up until now.....

I have an article from 1979 where many improvement in the construction techniques of masonry chimneys were detailed - but I'll bet not even 1 in 1000 masonry chimneys use them.....

anyway, that's just my opinion! I love masonry chimneys....for instance, I took 95% of these pics:
https://www.hearth.com/gallery/pics/chimney/index.html

but I do lament that much of the art - in terms of good masonry chimneys being built for the common housing stock - seems to have been lost.

 

[dvellone]

I guess I should be more clear.....

I personally love masonry chimney, but given modern technology I think square clay flue tiles are not up to the task....at least in colder freeze thaw climates. If I was to build a masonry chimney, I would look at either round flue tiles (stronger, better draft) or an isokern type:
(broken link removed to http://www.isokern.net/pages/chim/dmsys.htm)

Or even a masonry chimney with a poured in place liner.....

But when it comes to thin clay square and rectangle flue tiles - I am not a fan. I have had them fall apart when I try to cut them, etc. etc. and they are just not up to the task IMHO....

It's interesting because I grew up in an area where homes were built right, and many homes used round flue tile surrounded by vermiculite and other insulation which allowed expansion and kept them warmer, etc. - but, as you mention, the art was lost - mostly from post war (WWII) up until now.....

I have an article from 1979 where many improvement in the construction techniques of masonry chimneys were detailed - but I'll bet not even 1 in 1000 masonry chimneys use them.....

anyway, that's just my opinion! I love masonry chimneys....for instance, I took 95% of these pics:
https://www.hearth.com/gallery/pics/chimney/index.html

but I do lament that much of the art - in terms of good masonry chimneys being built for the common housing stock - seems to have been lost.

I'll bet that there aren't 1 in 1000 "masons" out there that adhere to standards of their trade, or are even aware of them for that matter. One of the most difficult items for me to find oftentimes was round flue tiles. Square tiles should never really be used as their draft ability is greatly reduced - the smoke wants to spiral as it vents upward and it keeps "bumping" into corners. Square tiles must be easier to make though or requested by more "modern masons" who thought they fit better in square block.

 

[cyclone]

Chimney was inspected yesterday and it is only the top flue. My mason is fixing it this weekend?

Questios though?

Would you use the pre fab chimney cap, or just make your own crown with the mortar?

Is there a special flexible mortar you use to bond the top flue and cap/crown together? If so please give brand and name so I can get some.


Any other suggestions would be great!!

 

[branchburner]

The tile needs to separate from the block for it's entire length- a complete airspace free of any mortar. The reason for this is because the tile will"grow" as it increases in temperature quite a bit more than the block. Clay tile and the outer shell will expand and contract at different rates causing exactly the kind of cracking you're seeing. Once the crack forms it will allow a substantial amount of water to enter which then, once temperatures plummet, will cause more severe spalling.

There are a lot of folks out there that think, mistakenly, that the tile needs to be mortared to the outer unit when in fact it is free standing and the space is instead filled with perlite, vermiculite or left as a void.

Not to hijack this thread, but how would thermal expansion apply to a ss liner that has been insulated with a poured in perlite/mortar mix? In such a situation isn't the clay tile now acting as the "outer shell" and the ss liner will want to expand and contract?

 

[cyclone]

Still looking for some answers??????

 

[dvellone]

Chimney was inspected yesterday and it is only the top flue. My mason is fixing it this weekend?

Questios though?

Would you use the pre fab chimney cap, or just make your own crown with the mortar?

Is there a special flexible mortar you use to bond the top flue and cap/crown together? If so please give brand and name so I can get some.


Any other suggestions would be great!!

I always make the cap in place but the pre-fabs can be decent quality if manufacture by a reputable concrete products firm. It depends on the competence of your mason. A poor mason will build an inferior cap.

If you make your own cap make sure the minimum thickness is at least 2 inches, 3"/ foot slope and with 2 1/2" overhang, use a liquid latex fortifier in place of water for the mortar mix, and most importantly cure it properly : cover with wet burlap and plastic so the mortar can slowly cure-not dry- for several days. Up high and exposed to the wind the mortar will dry out quickly and have little strength and weather resistance so a proper approach to the cure is essential.
If your mason is good he can do this easily and although it may cost a little more than a pre-fab unit it will be superior.

As far as sealant goes, use a closed cell foam strip as backer and back-up, and a cement stable sealant to close up the joint on top of the foam. The urethane sealants are durable and you'll find them easily at a good builder's supply.

A rain cap will keep water from dumping down the flue risking further damage.

 

[dvellone]

The tile needs to separate from the block for it's entire length- a complete airspace free of any mortar. The reason for this is because the tile will"grow" as it increases in temperature quite a bit more than the block. Clay tile and the outer shell will expand and contract at different rates causing exactly the kind of cracking you're seeing. Once the crack forms it will allow a substantial amount of water to enter which then, once temperatures plummet, will cause more severe spalling.

There are a lot of folks out there that think, mistakenly, that the tile needs to be mortared to the outer unit when in fact it is free standing and the space is instead filled with perlite, vermiculite or left as a void.

Not to hijack this thread, but how would thermal expansion apply to a ss liner that has been insulated with a poured in perlite/mortar mix? In such a situation isn't the clay tile now acting as the "outer shell" and the ss liner will want to expand and contract?

If I understand you correctly the liner was installed in the tile and the the remaining space between the tile and liner filled with mortar?
If so, and if the tile was originally mortared to the outer masonry you may still run into problems though I wouldn't think they would occur as rapidly.
The problem is that the clay tile expands more readily than block and bricks (not fire bricks). This is how clay, or refractory tile works or where it's strength lies - in it's ability to expand and contract with heating and cooling. It will still do this but possibly with the addition of the liner and the perlite/mortar it will keep it down to a rate slow enough to cause little damage- though little damage in an outdoor masonry structure quickly evolves into big damage. There really is no equal subsitute to an expansion joint. It's how all our great steel bridges are kept from collapsing at their point of anchor.
You've got a lot of factors going on in your application. By adding perlite to your mix you didn't make it's composition the same as the tile's so the dissimilar materials will expand and contract at different rates causing rupturing.
If there was a clean expansion joint along the flue tile's length the addition of mortar to the space between the liner and the tile will probably cause the tile to break where without the mortar it would have remained sound.

 

[blujacket]

Check out these products

(broken link removed to http://www.chimneysaver.com/crown_repair_products.html)

 

[branchburner]

I'm referring to the pre-mixed bags some people have used for insulation, Thermix I think? It seems insulateing the whole length of a liner with this would not allow for any expansion.
Myself, I have a crazy sort of hybrid insulation of both mineral fiber and loose perlite. But I capped that at the top with a few inches of mortar/perlite (and water repellent) in addition to the metal plate included with the liner. I'm now wondering if thermal expansion will crack that seal eventually.
My thinking is that a ss liner is going to expand lengthwise a bit, and perhaps compromise any seal where it exits the flue, maybe regardless of how that seal made. Will silicone between metal and masonry have enough give to not fail with thermal expansion over time?

 

[cyclone]

Okay, just so i know!!


When he removes the cracked chimney cap and flue, places the new flue in place puts on the new chimney cap he should fill in the void with a perlite and vermiculite mixed with the mortar.