chimney damage hidden in loft

[citizensmith]

Anyone got advice on this one?
We have been working to fit flooring in our loft above the downstairs breakfast room. The room is an old extension to the house and contains a chimney breast that passes up through the loft.
When we started it was incredibly filthy work and we were coming out black at the end of each session.
Now we can see better, i see a fair bit of damage to the chimney breast in the loft. It looks distorted, the bricks at the top in one corner are loose and separating and there is a 1/2 inch crack in the lime plaster running for about 5ft diagonally across the face of the chimney. When i poke a scredriver in the crack it dissapears completely - so is not just a surface crack.

The house is pretty big - this chimney breast has 3 flues in it and is very confusing to work out. The bit i am describing does not appear top be taking the full weight of the stack as it steps inwards at the top and then continues up for another floor.

Questions...

Do we...

1. Remove the loose bricks until things look more solid and then rebuild the loose corner.
2. Do we use conventional cement mortar?
3. If things are stable - can i simply repoint the crack and replaster to seal the chimney?

This part of the flue is connected to a rayburn which we do intend to light now and again - is this wise?

I am not sure if lining with a metal tube is much of an option as the total stack is 50 - 60 ft with 3 kinks to follow? Can this be done?


Sorry for the ramble, but i am fretting over this discovery :!:

 

[Nemesis]

Conventional cement mortar???

Eh??????

Explain... is this a Barratt Box???

What is conventional about cement?

 

[Lime]

Years ago this sort of cracking of the chimney in the loft was the cause of many house fires. It was particularly dangerous if there was a chimney fire.
chimney fires used to be common too.

As to what you do, it depends on how bad the stack is.
I wouldn't use cement, neither would I rip out bricks just because they can be loosened easily.
Obviously where the bricks are very loose and already coming away they have to be taken out and reset.
However wherever possible rake out the loose mortar and replace.

 

[Gervase]

It sounds as though it might be the result of movement or subsidence at ground level pulling one side of the stack downwards.
If I were you I'd remove the plaster where the crack runs and get in a surveyor. It may be a simple case of bricks being corroded by flue gases, but a five-foot crack is fairly large, and if it's running diagonally it does sound as though there's some movement.

 

[citizensmith]

The bricks at the top do need to come off in a controlled way before they fall off. They are not just loose, the whole corner is rocking. However, they are not bearing any load from above at that point. My main interest is to stabilise/secure it
I have been measuring up around the house trying to work out the actual stack thickness and i think it is remarkably thick (5 - 6 ft) total depth. Tis area now appears to be non load bearing from above, but the bricks are rotten and soft - but not damp.
I would prefer to use lime mortar if i can suss out what to do and get it sealed up and less likely to drop bricks through the ceiling!

This is a farmhouse and appears to have been subjected to more bodges than you can imagine. The only good side seems to be a policy of cover up and hide the problem so it becomes someone elses problem later!
I guess lighting fires in this bit of the house is right out of the question until i have a clear idea of what is going on.

 

[Lime]

citizensmith, brickwork is always more vulnerable where it is not taking load. It's more likely to get knocked and mortar joints broken too.
The workmanship and quality of brick used in "unseen" areas often leaves a lot to be desired which adds to the problem.

If it is taking no load then removing it will cause no problem.
Take it steady. You don't want to have an avalanche of bricks down into the fireplaces below.
However I would attempt to seal the fire openings just in case. Soot will get everywhere otherwise.

 

[middi]

There is no need to panic if you have an old chimney stack which is loose, showing cracks and looks unsteady but is still standing up by itself.

All you have to do, starting from the top, is rake out as much as you can of the loose mortar, even if you have to go as deep as 2 or 3 inches in places, repoint with lime mortar and replace the odd spalled brick as needed, do not worry if some as the brick gaps are slightly larger in places. when you have finished it will all be part of the character, it will not look new or rebuilt and it will last for another 150/200 years and blend with the rest of the old building in perfect harmony.

Whatever you do avoid at all costs, if you can, to dismantle and rebuild.

Understanding old chimnies, to the untrained eye, is like looking at very old oak beams with lots of woodworm holes, they are a lot more stronger than you give them credit for.

Conservation can be time consuming but it is worth the effort if done correctly.

 

[citizensmith]

Thanks for that advice and support, i feel a lot more confident that we can fix it ourselves without making the house fall down. Its just another "unforseen" job that stems from another job etc etc!
I suppose thats why we bought the place in the end!