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Scuba diver 01-11-2019 01:34 PM

Cracked chimney
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Hi all
I have recently finished an outdoor fireplace, gas fired. Not sure if the owner is lighting on low or straight to high. This burner is 180000 btu's chimney is red brick with a two coat stucco system. It has precast concrete face(haddonstone product).from top of firebox chimney is 6'tall, cap stones are about 6" above flue liner. Problem occurred shortly after the owner stsrted using it. It cracked from tge face stones to the top. Any ideas on why?

Scuba diver 01-11-2019 01:45 PM

Trying to figure out if ignited on high would crack it, by not allowing the unit to warm up slowly

fjn 01-11-2019 07:22 PM

Was a 1" air space maintained between flue liner and surrounding masonry ? Flue liners when heated, expand both in width and height. That expansion can exert stresses and crack both the liner and masonry.

Scuba diver 01-11-2019 08:51 PM

There was a gap maintained until the last few crs. of brick, i also had not noticed a crack in the liner but will take a closer look

Fouthgeneration 01-12-2019 05:19 AM

The good news this isn't inside a 500,000.00$ home waiting to cause a fire....

No scaffold needed to tear it apart....;)

I suggest you find a competent fire place builder to teach you how, for either direct payments or some sort of labor exchange for schooling in safe to use fireplace construction techniques.

Some studying on line and at a library might help some.

Pretty Fire place, Where is the roof to keep it BONE dry?

In Argentina, in the Pampas? ranch land, the out of doors cow cookers/summer time kitchens have ROOFS, but the walls are rolled up tarps, thus allowing the fire places to survive several winters.....

Even a properly built fire place will explode/suffer damage if it is hot fired when wet or damp. :sad:

JBM 01-18-2019 05:11 PM

How did you build the smoke chamber, did it have it's own walls behind the outside masonry?

There isn't a damper right?

JBM 01-18-2019 05:14 PM


Originally Posted by Fouthgeneration (Post 7453067)

Even a properly built fire place will explode/suffer damage if it is hot fired when wet or damp. :sad:

I had a small bit of puddling at the joint where the bluestone met the fire brick. A chunk of the bluestone exploded!

bytor 01-19-2019 08:58 AM

Any angle irons in there which lack room for expansion? It's amazing how much lateral pressure expanding metal can exert... Dampers included.

Fouthgeneration 01-19-2019 07:35 PM

bytor, I'll use some rolled up fiberglass to form a cavity for the steel and iron embeds to grow into , instead of 'jacking' the masonry apart.

the flues need to able to move up to 2" vertically on a 2 story home during a chimney fire.

I like using stainless steel positioners cut out of 18-20 gauge stock that allow the flue to move up and down and grow some what around during fireplace/furnace use.

The flue needs a soft sliding joint around the cap, especially with poured caps, I have repaired several that had the cap elevated by thermal expansion of the flues.

JBM 01-19-2019 09:22 PM

Another non returning poster, building something wrong...

fjn 01-20-2019 12:48 PM


Originally Posted by Fouthgeneration (Post 7459157)

The flue needs a soft sliding joint around the cap, especially with poured caps, I have repaired several that had the cap elevated by thermal expansion of the flues.

Yup ! :thumbsup: Like depicted here.

Windycity 01-20-2019 04:17 PM


Originally Posted by JBM (Post 7459243)
Another non returning poster, building something wrong...


In the description it says that he is a mason

Sent from my iPhone using Tapatalk

Scuba diver 01-20-2019 10:05 PM

This was built to architect specs, i thought this was a place of professionals not sarcastic dimwits

Tinstaafl 01-20-2019 10:18 PM

Maybe you didn't notice the disclaimer on the architect's drawings? He takes no responsibility; you, as the builder, carry the burden of making his pretty design actually work.

These "dimwits" have been down that road many times. Stick around, you may learn a thing or three. :thumbsup:

Fouthgeneration 01-21-2019 06:25 PM

OPer= "And He Built a Crooked house....."
R.A. Heinlein

Nehemiah 2:17-18
Then I said to them, "You see the bad situation we are in, that Jerusalem is desolate and its gates burned by fire. Come, let us rebuild the wall of Jerusalem so that we will no longer be a reproach." I told them how the hand of my God had been favorable to me and also about the king's words which he had spoken to me. Then they said, "Let us arise and build." So they put their hands to the good work.

Next time read the directions, then put it together....:rolleyes:

Have you ever seen a twenty year old roofless fireplace that STILL WORKED????:no: Where it rains every few years?

See ASTM C 1283 v2015...

superseal 01-21-2019 06:32 PM

For sure the damage looks heat in very high heat. 180,000 btu's will heat a friggin' 2500+ sq ft this not a typo? If you're indeed correct with the size of this unit and your customer fired full steam...and perhaps the fireplace was soaked through...more than likely, as it's been a very wet year for many, you're lucky chunks of it aren't laying in the neighbors yard :laughing: And, as mentioned by other dimwits, any steel e.g dampers, lintels, reinforcement will expand and cause stresses.

I'm leaning towards a very wet high fire...the design may be purrty to look at, but with that graceful swale of the throat and flue section and the ledges present, that baby is inhaling some serious H2O.

The mason in you can surely attest that adding water is the trigger for flaming bluestone with high won't quite pop without it...

Fouthgeneration 01-21-2019 08:33 PM

Remember the first piece of clay you fired that wasn't oven dry? it exploded and broke five of your classmates projects in the kiln....

Did you install a damp proof flashing/vapor barrier course under the fireplace???

JBM 01-22-2019 10:24 PM

If you have progress photos we can iron this out.

Scuba diver 01-23-2019 08:33 AM

I have no in-progress photos

Scuba diver 01-23-2019 08:37 AM

There is no damper, one angle iron 12" above opening with plenty of room for lateral expansion, the crack seems to start at the top.
There is a cap to keep rain, snow and ice out

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