Newbie in London

[dave36]

Hello, just though I'd say hi, great forum.

Have built the foundations, getting a started on the base soon (concrete block / paving slab) with a 15cm vermicrete layer plus 5cm calcium silicate (perhaps overkill...thoughts welcome). Then off to kilnlingings for the firebrick and arch....

Will share a photo when I work out how....

D

[lovepizza]

Hi Dave,

IMO, the vermicrete is an overkill. You can argue that you can never have enough insulation but 15cm of vermicrete will take months to dry out, even in good weather conditions. The vermicrete must be totally dry before you continue with the dome build to avoid heating up/ heat retention issue later on. With Autumn upon us, I would not expect to be cooking pizza until at least the spring with your proposal.

If I were you, I would half the Vermicrete and go for a thicker Board. Alternatives, scrap the vermicrete altogether an go for 2" of silicate of vermiculite board. If you can avoid the need for drying times of vermicrete, you will speed up your build 3 fold.

[dave36]

Lovepizza

Thanks, you've got me thinking (and reading even more of this forum). Agree, 15cm of Vermicrete is a bit much and may not dry by the time I plan to lay the hearth (this side of xmas, dome to come in spring).

Thoughts welcome - I've got 21cm to fill - now thinking 64mm of (any old brick just to fill up space), topped by 10mm of Thermalite block, topped by 50mm of CalSil board (after which fire clay mix and then fire brick). I'll keep the below-fire brick level completely dry, no cement etc.

Cheers guys & girls

D36

[lovepizza]

Dave,

You're on the right lines. Thermalite is a good insulator in itself. I made my oven door from Thermalite and it withstands 350c ambient temp with no issue.
Pop some Calsil board on top of them and you'll be good to go. I used 7 cm vermicrete on top of some council slabs, then a 25mm vermiculite board to take the firebricks. Calsil board is several times more efficient than both vermicrete and vermiculite board (I am sure someone will let you know you how much). Either way, 50mm calsil probably twice as efficient as your 150mm of vermicrete. Just check when you buy , if you need to take care when cutting it by wearing appropriate mask (can't quite remember).

Also, no need to cement in the fire bricks with fire clay (if that s what you are proposing). Keep them loose but snug. It easier to replace one in the unlikely event that one cracks. Also, it gives you a nice level surface if it the firebricks go straight onto board. You don't want that pizza peel catching!

Let us knows how you go..