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  #11  
Old 03-14-2014, 02:00 AM
Peasant
 
Join Date: Jul 2013
Location: Debden Green, Essex
Posts: 27
Default Re: opinions on techniques for dome waterproofingr

Hi, I'm in the process of my first oven build right now. Monolithic cast refractory (1400C) dome. Casting tomorrow if today goes to plan.!!!
Done loads of research and got some great info from this forum. Now the foil comments have given me something to ponder.
For the floor I am putting 3" firebricks onto a 3" thick Calsil. Levelling the bricks down with a fireclay/sand paste onto the Calsil.
I have been advised to cover the Calsil board in aluminium foil to prevent it absorbing the moisture from the clay paste.
I have also been advised to foil over the dome insulation blanket (foil under chicken wire) to avoid sucking moisture from the final render.
Seemed like sound advice, but what do you guys think?
I have already prelaid 2" of vermicrete onto the stand, so I was going to completely wrap the Calsil board in foil.
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  #12  
Old 03-14-2014, 03:16 AM
cobblerdave's Avatar
Il Pizzaiolo
 
Join Date: Jan 2010
Location: brisbane australia
Posts: 2,383
Default Re: opinions on techniques for dome waterproofingr

G'day
A bit of moisture from the clay paste is not a problem at all. It's the fact that the dry insulation sucks the moisture from the paste making it bloody hard to use a notched trowel to get a leveling surface that's the real issue.
I just used a smear of table margarine on the insulation stops this and keeps the paste workable so you can get on with the important task of getting a level hearth floor.
Your ovens an organic beast. Moisture is part of it. Your wood will contain 20 per cent moisture anyway, were do you think that ends up?
The trick is to stop large amounts rain etc from getting in. But the stuff that you get naturally from the air and wood must be able to get out as well. Forget the aluminium
Regards Dave

PS the oven sounds cool ... How about some build pics
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  #13  
Old 03-14-2014, 04:38 AM
Peasant
 
Join Date: Jul 2013
Location: Debden Green, Essex
Posts: 27
Default Re: opinions on techniques for dome waterproofingr

Thanks Dave. Build pics will follow.
If the Calsil absorbs water, will it swell and offset my firebricks?
What about ambient moisture/rain getting at the entrance and wicking into the oven floor?
Had another chat with supplier this morning - they say encase the Calsil board completely in foil and put the fire bricks down loose without the fireclay?

Cooking dome will be a one piece casting, 40" internal, 4"thick, cast on a form of sand covered with wet newspaper. And some wooden arch forms.

The flue arch will be cast separately. This to give the option of different positioning.

I'm torn between different schools of thought:-
To provide a thermal break or not between dome and flue arch??
I've seen David S mentions Vermicrete insulation here. Since I'm going to so much trouble and expense for thermal mass and good casing insulation, I want to retain as much heat for as long as possible in UK weather.

I like this idea, but with a minimum recommended castable thickness of 2" and approx 1" of insulation, I'm looking at the flue being 3" away from the cooking dome entrance. Also the flue needs to get hot for a good draw.
Would this distance and insulation affect the draw??
Going for an 8" flue.
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  #14  
Old 03-14-2014, 06:59 AM
boerwarrior's Avatar
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Join Date: Apr 2013
Location: Santa Rosa, CA
Posts: 447
Default Re: opinions on techniques for dome waterproofingr

pikemonkey

I and several others on this forum used nothing at all between our CalSil insulation and the floor fire bricks. If your CalSil is level and your bricks are close to the same size then "leveling paste" is unnecessary. Remember that there is not such thing as 'perfect' (well, except for Les!) in a brick oven anyway.

If you do need some leveling you can use dry brick dust. Once you start using your oven the ash gets down between the bricks and kind of locks everything into place anyway.

You asked a lot of questions in one post!

Good luck!
Neil
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  #15  
Old 03-14-2014, 07:25 AM
Peasant
 
Join Date: Jul 2013
Location: Debden Green, Essex
Posts: 27
Default Re: opinions on techniques for dome waterproofingr

Thanks boerwarrior.
All noted thanks.

Yup - asking a lot of Qs, and condensing them into one post, since they're the only ones I have right now.

Just trimmed some Calsil up so will try an offcut in water and see what happens to it.
Since we have a fair bit of wet weather in the uk, I want to make especially sure the oven floor doesn't fail. I do like to over engineer!!!

I have laid foil under the Calsil, but reckon I will take your comments on board and place bricks loose on top, without foil here. See how flat it all is.
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  #16  
Old 03-14-2014, 07:26 AM
Peasant
 
Join Date: Jul 2013
Location: Debden Green, Essex
Posts: 27
Default Re: opinions on techniques for dome waterproofingr

Also the wife's just come home and I've had to sneak the margarine back in the fridge!!!
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  #17  
Old 03-14-2014, 09:46 AM
david s's Avatar
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Join Date: Mar 2007
Location: Townsville, Nth Queensland,Australia
Posts: 4,787
Default Re: opinions on techniques for dome waterproofingr

If the calsil gets wet it does not swell. It dries out and is not affected.
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