Finished the hearth - Some questions

[tdibratt]

Hi, I have just finished the hearth. 4 inches of concrete followed by 2 inches of vermicrete. I kept the concrete around the perimeter about 6-8 inches for strength when it comes to closing it in.

I am going to be putting on 2inches of KFAC-19 fibreboard, so plenty of insulation. Question is how soon can I start the cookibg floor? I am worried I might trap mositure under the fibreboard, or can I start the next day and it will eventually disspipate on it's own?

Also, thinking ahead. I am building the 36 inche high vault oven with the 18 inch dome height. The door will be 19 inches wide. Plans reccomend 12 inch door height. If I go with the arched dome, I notice most picture seem to have 3 bricks on their flat so I figure about 8.5 inches of height before they start the arch. Going from 8.5 to 12 in the center is 3.5 inches. Is this correct? The picture would let me believe the center arch is higher than 12 inches to give the arch more of a pronounced curve.

Thx

[Antonio D.]

Hey Tony
I went with a low vault 36". my opening calls for 18" x 10".
I stayed at the 10" and came down from that.
I went with 3 firebricks on the flat (they are 2" each) then tapered up to 10".
The more open you are at the top the more heat you will lose.
My oven has been in use for a week now, so far with no internal cracks and cooking 3 minute pizzas.

Tony
Here is a link to a photo
http://www.fornobravo.com/forum/phot...1_IMG_0341.JPG

[tdibratt]

Oven looks nice. You did what I am hoping to do on the facade with an arch brick and a center keystone that is bigger than the other bricks and sticks forward a bit.

I am doing 19 x 12 opening. So I guess I should just use my 2.5 inch bricks with a thin joint line probably taking me from 8 inches to 12 inches at the top of the arch.

Thx

[Les]

Originally Posted by tdibratt

I am worried I might trap mositure under the fibreboard, or can I start the next day and it will eventually disspipate on it's own?

I would give the concrete a few days to cure, then go for it. Any moisture will work it's way out before you are done with the build.

Les...

[mfiore]

Originally Posted by tdibratt

I am going to be putting on 2inches of KFAC-19 fibreboard,

Have you had a chance to play with the KFAC-19 board? I'm considering purchasing some, but have yet to see someone who has used it. Curious how it holds up if it gets damp.

[Antonio D.]

Yes I think going from 8 inches to 12 inches at the top of the arch would work good. Just make a form ( I made mine from 2" styrofoam) the size you want for your arch and follow on both sides till you meet where your key stone will be.
I used architectural block for my base. The key was cut from a 1/2 block I had leftover.

Tony

[tdibratt]

I have not used the KFAC yet but have purchased it. Cannuckjim I think mentioned in a post somewhere that he had used it.

I hope it will not be a problem if it gets damp.

Not sure if anyone else has any experience with it.

[mfiore]

I think he mentioned using Insblock-19. It's been suggested that they are the same product, but in searching product specs, they have differences. If you can spare a small square, it might be worth stacking some heavy block on it and getting it wet to see if it holds its own. You don't want to find out down the line that it turns to mush if it gets wet.