Cracked chimney stack

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I've noticed our chimney stack as a small vertical crack down it. I'm not sure how long it has been there though.

I had two roofers visit to quote on some slipped tiles and asked their opinion on it.

One told me that it could be patched with cement to stop it worsening.

Another told me the chimney would need re-bracing at a cost of around £200 - £400 and could be between 1-5 years before it gets worse.

I've checked in the loft and I don't see any signs of damp or the crack travelling underneath the roof line. I also don't see a crack on the other side of the chimney stack.

I have attached a picture:


One of the chimneys in the stack is used for a gas real flame fire, I read online this cracking can be due to heat?

I'd appreciate others opinion on this as the two roofers had different opinions.

Thanks
Martin
 
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It could be a historic crack, but it would be a good idea to point it up and then see if it happens again, I think.
If it does, a steel band will help a great deal to keep things stable.
At this height, heat from a gas fire isn't an issue.
John :)
 
Hi John,

I'm not sure if its always been there or just appeared, didn't think of pointing it to confirm if it cracks again and is still moving.

I was think pointing it would stop water seeping into it and cold cracking it further due to the water expanding.

Thanks
Martin
 
1. When was the house last surveyed? Such a defect would have come up on a survey.

2. What is the flue, nearest to the crack, venting - or is it sealed below?

3. Has any portion of the c/breast on your side or your neighbour's side been removed?

4. Didyou see the examining roofers inspect the flaunching for cracks or perishing or loose terminals? I doubt it because the flaunching is difficult to access, being about six foot above the ridge.
Someone should look up there.
Only allow inspections from a roof ladder(s) on a slate roof.
What does "re-bracing" mean? Perhaps strapping as suggested by burnerman.
The flaunching and oversail appear greenish - signs of holding moisture.


5. A gas terminal is visible with a vent ( 12" x !2" terracotta? ) below.
Something odd here. Does the gas flue have a SS liner?

6. The matching front flue on your neighbour's side, is it active or redundant?

7. There are signs of non-historic pointing low central front, which would indicate that the crack occurred after the pointing.

8. I'd suggest discussing it with your neighbour, and smoke testing any open flues on both properties.

9. As a temporary measure you could fill the crack with caulk. In the long run i suspect that a partial rebuild is required.
 
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A couple of Helifix bars would be best.
 
1. When was the house last surveyed? Such a defect would have come up on a survey.

The house was surveyed in 2004 when we moved in and nothing was mentioned.

2. What is the flue, nearest to the crack, venting - or is it sealed below?
It is venting and the chimney breasts below it also have vents in them to allow airflow and avoid damp.

3. Has any portion of the c/breast on your side or your neighbour's side been removed?
Our Neighbours have removed some of their chimney breasts if not all.

4. Did you see the examining roofers inspect the flaunching for cracks or perishing or loose terminals? I doubt it because the flaunching is difficult to access, being about six foot above the ridge.
Someone should look up there.
Only allow inspections from a roof ladder(s) on a slate roof.
What does "re-bracing" mean? Perhaps strapping as suggested by burnerman.
The flaunching and oversail appear greenish - signs of holding moisture.
I believe he meant banding to hold the stack together but I can confirm that. Both the roofers were looking at the slipped tiles and only looked from the ground at the chimney stack. To be fair I only asked them for a quick opinion on the stack and then thought of posting here as I've had helpful answers before

5. A gas terminal is visible with a vent ( 12" x !2" terracotta? ) below.
Something odd here. Does the gas flue have a SS liner?
The gas terminal was fitted as prior to that we had a bird come down the chimney and out of the fireplace. That gas terminal was the only one approved for the real flame gas fire we have. This was fitted before we moved in so I am not sure if it was tested or lined (I don't believe it is lined).


6. The matching front flue on your neighbour's side, is it active or redundant?
That one is redundant.

7. There are signs of non-historic pointing low central front, which would indicate that the crack occurred after the pointing.
We haven't had any pointing done so this must of been done before we moved in.

8. I'd suggest discussing it with your neighbour, and smoke testing any open flues on both properties.
good suggestion

9. As a temporary measure you could fill the crack with caulk. In the long run i suspect that a partial rebuild is required.
My main concerns are its structural stability and the gas exhaust escaping, the smoke test you suggested should confirm one of these

I am beginning to wonder if the stack will actually need a significant repair, the slate roof is pretty old and I don't really any work on the stack to mean the slate roof has to be replaced.
 
1. So the crack occurred after 2004 - when did the neighbours remove their c/breast (s)?

3. Did you grant permission and retain a copy of any party wall agreement?If possible could you view your neighbour's loft and look for cracks and how the remaining c/breast is supported.

4. Perhaps do the things i suggested above and instruct whoever inspects to take photo's. Do not have any chimney sweeping done.
I'd submit that it's too early for banding or stitching, until you have a better idea of any cause (s).

5. A separate issue , perhaps post the photo and info about the terminal and real flame fire etc. on the plumbers forum for GRI's views.


9. From what i can see and what you say, there is only one gas appliance venting thro the gas terminal - smoke test that flue as well.

Your roof is in good shape, but willy nilly you will have to do something. Expediency is spelt expensively, and from the details so far first find out what is happening then make a decision about further works.
 
That's a thermal crack from expansion.

Basic repointing is not even an option. Helical bars may be, but the problem with that crack in that exposed location, is that it will be open to flue gases from the back and will be open behind any surface repair too.

By the time you've had it properly assessed for suitable crack stitching, and then scaffolded and work done, then you may as well have a proper repair (part rebuild) done
 

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