Building a chimney

[DaveS]

Hi Folks.

A simple question, if you know, I'm sure!

I've bought a woodstove and currently have no chimney, so I'm building one!

I was going to use the chimney blocks that are readily available at the builders merchants, supporting the stack on a pignon at the bottom and a chevetre at the top. The question I have is, do I need to use any special mortar to 'stick' the blocks together or will a standard cement based mortar do?

I am going to use the nice shiny inox tube from the poele to the chimney and a slightly cheaper version up inside the blocks to the top. The chimney will start in the downstairs ceiling, probably surrounding the pipe with some fireproof plaster board .... when I get round to putting a ceiling in!

When the stack emerges on the roof (to go 40cm above the ridge line) i was going to render it and fit some sort of 'flashing' to make it water tight over/around the tiles. Any advice on what products to use for this 'seal' would be helpful too.

Many thanks

Dave

[Bob T]

Just did the verysame job 3 weeks ago. I used standard concrete squares, with standard morar. I have put a flexi flue liner of 180 mm up the hole. Bought a proper concrete cap for the top and intend to use tonpier coloured crepe for the outside. On the ceiling I fixed a stainless steel square with a 180mm hole in it to which I connected the inox pipe from the bottom and the flue liner from above. I also bought a zinc roof seal plate from Brico Depot and fitted that around the chimney to stop any rain getting in.

We have had it lit a number of times and it works great. The only problem that I encountered was my wife telling me that I should not be on the roof as it is too high. I survived just to prove her wrong.

[The Builder.]

PLEASE people remember ecart au feu min. distances from ceiling combustibles.

http://boutique.cstb.fr/dyn/cstb/upload/fichiers/ext_cheminee.pdf

[legs_akimbo]

Very important of course to ensure that the seal around the chimney is watertight, this will consist of a front apron, side flashings, possibly with soakers depending on which tiles you have, and a back gutter. All cut from code 4 lead. Could not really describe in words here how it is done but "Calders" the british lead manufacturers do a small booklet free of charge that has diagrams and instruction for cuting and dressing chimney lead, also for a few quid a more advanced booklet that may be very handy. As for rendering the chimney once the lead flashings to front sides and back are in place they can be secured with 40mm washered masonary nails and then a bell cast stop bead can be set two inches below the top of the lead and angle beads (stainless steel or pvc) to the sides, then a scratch coat of mortar folowed by a finish coat containing waterproofer. Once this has cured the front apron side soakers and back gutter can be cut and fixed with the tiles reset.

[DaveS]

I've now got to the stage of having my blocks up through the ceiling and roof and in the process of rendering the exterior. I bought a few bits from Gedimat to support the chimney downstairs (a metal support for a chimnee pignon), a chevetre for going through the roof and an embargement to seal the roof.

I have a couple of questions though .....

Is there something I should buy to hold the flue pipe in the centre of the chimney ... or doesn't it matter?

Is there some sort of clamp or connecting thingy to hold the sections of inox pip together? Or just plug them together with perhaps a little refractory mastic?

Many thanks

Dave S