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Advice on lining an old chimney


Araucaria
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I'd like to put a flexible s/s liner into an old chimney - built about a hundred years ago - that has never had one before.

What concerns me is the top of the chimney. The brick construction ends before the chimney goes through the roof. On top of the brickwork there are a number of hollow terra-cotta pre-formed sections, much like what you find inside a more modern chimney construction. They are an oblong cross-section and after they exit the roof they have been rendered - several times I'd say - and make a reasonably water-tight join with the roof. The roof is lauze (stone) and I don't want to disturb it more than is necessary.

Will the terra-cotta sections be strong enough to support the liner (ie the clamp that goes across at the top)? How do I get a reasonably water-tight finish around the liner at the top? The problem is that the terra-cotta sections aren't very thick. In an ideal world no doubt the chimney would be brick all the way to the top.

Further up I was hoping to put on one of those chinese hats: do they need to be supported by a short section of rigid s/s pipe, or can they be fixed directly to the liner?

Normally I'd look and see what other people have done - though with chimneys that's a bit more difficult. These terra-cotta chimneys do exist elsewhere near here, but they all look as if they are still unlined, and the way they have been made to stop rain coming down is by having a couple of mechanical tiles stoop up in an inverted "V" on top - mortared in, of course.

I feel that any way of getting a liner in the chimney will be better than what I have. But I'd really appreciate practical suggestions for finishing off the top.

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The terra cotta section are easily strong enough. If you are concerned at the point load from the tube clamp add something to spread the load further. A friend has just done this and the terra cotta pots run 7m to the roof, no bricks.  I have seen all manner of flaunched in bodges, own one myself done by masons.  I have seen flat dalle type stones with holes to take the liners in some shops so they do exists although I was going to use creasing tiles in the traditional British way myself as i like the added detail.

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Thanks Teapot, that's very helpful. We don't have anything like 7m in terra-cotta - more like 1.5m. The chimney isn't quite up to the ridge level. I am a bit more confident I can do it!

Do you know about the "chinese hat" rain covers? They have three legs each of which ends in a fork, with a hole in to take a screw/bolt. I wonder if they would simply tear the flexible liner in a gale, and if they need to have a bit of s/s rigid pipe inside to support them.

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