Chimney Lintal

dande

I have an old house with a large fire place and a very wide chimney that the rain and wind come down. I'm putting in a stove whats the best way to close off around the flue to stop the weather coming down.

I don't really want to open the chimney if I can avoid it or make the fire place thinner as its a nice feature

Poor Uncle Tom

Why not clean your chimney, put your stove in place and connect it to the chimney pot on top with a double walled flexi metal flue liner. There is usually a joiner at the top that seals the liner to the pot using a large jubilee clip and a cap is fitted. Ask the stove suppliers for more information.

dande

Thanks. I'll look at that. But I will lose a fair bit of heat up the chimney

The Parrot

if its a good stove you shouldnt do.

Poor Uncle Tom

The Parrot wrote: »

if its a good stove you shouldnt do.

I think the op means the chimney is so big that a lot of heat could be lost up around the flexi lining pipe inside the chimney space.

If that is what you mean, the flexi liner would be sealed to the pot on top and you could always seal off at the base inside the chimney also by putting a framework of metal studs horizontally in place and finish in fireline board, like fireproof plasterboard. You can insulate above this with rockwool.

This volume of space between the flexi-liner and the chimney needs to be vented to stop condensation causing damage.

dande

Thats brillient, thats exactly what I'm looking for. Do you know where I would find a detail of this. Thank you so much for your help.

Poor Uncle Tom

dande wrote: »

Thats brillient, thats exactly what I'm looking for. Do you know where I would find a detail of this. Thank you so much for your help.

I've done those details for clients in the past few years, I wouldn't feel happy giving a detail without having seen a job, each job is individual.

So, imo, you need to get a specific detail from any good local AT. A generic detail may work, but when you are balancing condensation, ventilation, insulation, heating and fireproofing why risk it.

martin46585

I think it's a register place or similar which you looking at, so a quick google image will show some examples,
Ideally you would install a twin wall flexi flue suitable for solid fuelled stoves,
The register plate will close down the opening to the size of the flue, which then will allow you to fill the void between the flue and the original opening, with a loose fill material such as silvaperl, which will easily flow down from the chimney cap, right to the register plate.
The benefits being two fold, in that it will reduce condensation on the flue and more importantly will greatly increase the draw on the flue as it will insulate the flue, and also stop the flue from rattling..

dande

That is exactly what I was look for because I want to back fill around the flue. I presume I'll have to get the register plate custom made.

How heavy is the back fill, would fireboard support it.

martin46585

The loose fill material is very light weight, though the material used is usually a sheet metal of sorts,
The gauge and type will depend on the size of the original opening to be closed down,
A decent steel fabricator will be able to cut and fold a plate with a cut out for the flue, from stainless steel plate or similar....

Poor Uncle Tom

The only problem I could see with completely filling the void around the flue liner is that the liner only has a limited lifespan and if the stove is being used regularly the liner will need to be changed at some point. What happens the fill? will it solidify?

martin46585

The 904 grade of liner will have a 20 year plus warranty and so ideally will last much beyond this, as for the fill, in the event that the liner should have to be changed, the loose fill will have to be collected, through the flue hole when the liner is taken up, as it will still be in loose granular form.

Hardly the end of the world....eggs and omelettes if you will...