vermiculite and chimney stack advice

cigamseinnub · 23 Sep 2011

hello
having a chimney built its a concrete linear with vermiculite infill to chimney stack, read on the bag the vermicuite comes in that it can be used with cement mix for infill ,the bricky however says that on all the work hes ever done on chimneys they always pour the vermiculite straight in .The brickys a good bloke and i believe thats how it can be done as well but wondered if any one has an opinion which is better using vermiculite straight or as part of a dry mix sand and cement. as at £20 a bag it ain't the cheapest of material.
on that note anyone know of cheap place to but vermiculite in the cambridge area

cotswoldbuilders · 23 Sep 2011

If I was building from new, I would have mixed it with cement, however nothing wrong with adding without.
It is a good insulation material, making the flue warm up quicker.

geraint · 23 Sep 2011

The brickys a good bloke and i believe thats how it can be done

So why are you now calling him a liar

cigamseinnub · 23 Sep 2011

thanks for the response but please read the post before responding , im not calling him a liar i just said that its also possible to use it as a cement additive rather than neat . and was asking if anyone had another opinion about which is better ,as cost can be reduced by mixing with cement.

please if i missed something can you point out where i called him a liar just asking advice/opinion thought that what the forum was for
so what do you think then geraint straight or mixed as infill

geraint · 23 Sep 2011

cigamseinnub said:
thanks for the response but please read the post before responding , im not calling him a liar i just said that its also possible to use it as a cement additive rather than neat . and was asking if anyone had another opinion about which is better ,as cost can be reduced by mixing with cement.

please if i missed something can you point out where i called him a liar just asking advice/opinion thought that what the forum was for
so what do you think then geraint straight or mixed as infill

Mixed.... as I would not trust you as a client.... and would not work for you...

If you cannot trust your builder, you should not be employing him...

Should you not have asked the question before you hired him....

,the bricky however says that on all the work hes ever done on chimneys they always pour the vermiculite straight in

and was asking if anyone had another opinion about which is better

Alastairreid · 24 Sep 2011

cigamseinnub said:
thanks for the response but please read the post before responding , im not calling him a liar i just said that its also possible to use it as a cement additive rather than neat . and was asking if anyone had another opinion about which is better ,as cost can be reduced by mixing with cement.

please if i missed something can you point out where i called him a liar just asking advice/opinion thought that what the forum was for
so what do you think then geraint straight or mixed as infill

Ignore the thing called gerunt aka the forum troll.

Nige F · 24 Sep 2011

geraint said:
The brickys a good bloke and i believe thats how it can be done

So why are you now calling him a liar

Nige F · 24 Sep 2011

geraint said:
[ I would not trust you as a client.... and would not work for you...

So he trusts no one - how`s Jolly Green Geriant get any work then

stuart45 · 24 Sep 2011

There are 2 main reasons for adding cement to the insulation materials.
Firstly making perlite or vermiculite into a lightweight concrete makes the flue liners more stable when it comes to having them cleaned. Years ago normal mortar was used.
Secondly the insulation won't settle leaving cold spots higher up the flue.
Perlite should be about 10/1 mix, vermiculite about 6-8/1.
A lot of bricklayers don't bother with cement, although it is worth doing.

theoldun · 24 Sep 2011

Without writing a history on flues and how to form them. On a new build, if insulated clay or concrete liner specified you always surround the liner with a semi dry mix of 1 to 6 or 9 of cement and vermiculite.

Two reasons. 1. If you are changing direction or blinding the light, you can not support liner on bottom corbel of flu, nor can you cover the liner on shaped top cut angled corbel of the flue.

2 On straight sections of flue, with no cement in vermiculite the flue would be alive and subject to movement.

In the same way that you add cement to sand or ballast, you also add it to vermiculite to form a light weight insulated concrete.
oldun

cigamseinnub · 26 Sep 2011

thanks for the response the bricklayer has done a good job on building the house and exellent work on the fireplace , he said hed add cement if i wanted it was just he has always done it straight infill on sites.from what stuart45 and oldun say i will see about having cement added in .as i thought that having a liner in the cimmey with loose fill means all the liners weight is just supported by the linner below as with cement added you gain extra stabilty from the infill.
final questioni even though the cement-vermiculite seems to be recomended as a dry mix is water added if so wondered how much
( learnt hard way on beam an block floor that dry mix doesnet always mean dry as it just brushes straight through grr its says dry but means damp)

geraint i'm so confused first you say trust the bricklayer then you say you would mix oh me heads in such a spin do i trust the word of my bricky or you oh being a poor layman is so hard and obviously the word of an artisan is LAW

ps just to be clear i do trust my bricklayer and dont think hes a liar

RedHerring2 · 26 Sep 2011

When I did mine I used a semi-dry mix. Too much water and the vermiculite tends to float. Too much water also adds to the amount of water that oozes out the bottom.

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vermiculite and chimney stack advice

geraint

geraint

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