Hello from UK

[RyH]

Hi, I am almost ready to build my oven, just finished laying the 4" vermiculite concrete insulating layer on the heath. Certainly is odd stuff to work with. How long does it take to cure and how hard will it go?
Should I place the oven floor directly onto this or put down a small layer of concrete first?

Any advice appreciated.

[dmun]

You want to put a layer of powdered material, a mixture of fireclay and sand is traditional, but a layer of dry mortar mix will work just as well, to level the surface. Put the bricks down dry, and correct any that stick up. When you get the floor where you want it, fully wet the floor bricks to firm up the underlayment.

Welcome to Forno Bravo. And yes, vermiculite concrete is odd stuff.

[dusty]

Hi Ry, and welcome to the forum - I've found it to be a very good place.
Congrads on the oven hearth. That vermiculite is odd stuff. Even when the cement cures it is still a bit like styrofoam. You could push a screwdriver into it with no problem, so treat it nice and try not to let it get wet.
Very important to lay the oven floor directly on top of the vermiculite layer. Some builders have used an insulating ceramic board (available from Forno Bravo store at a reasonable price) under the floor for insulation. I didn't. I used the vermiculite like you, but now I am sure that I loose most of my heat through the floor. If I had to do it over again, who knows. Mine works great. If you desire the oven to hold it's heat for as long as possible, you may consider the FB board. If adequate is fine, then save the $ and go with what you got.

Either way, have fun and keep us posted. Any questions are welcome. We have all been there.

dusty

[RyH]

Thanks Dmun and Dusty. I'm using a modular oven so the oven floor is made up of 4 sections plus the landing. Is it still ok to place directly on top of the vermiculite as suggested?
I'm concerned it will not hold the whole oven, as Dusty says you could easily push a screwdriver through it?

I do not want to get it wrong but also can't wait to cook a pizza!

[Xabia Jim]

Originally Posted by RyH

I'm using a modular oven so the oven floor is made up of 4 sections plus the landing. !

Welcome to the FB european time zone.....

sounds interesting....how about a picture or two?

XJ

[Frances]

The vermiculite layer does hold up the oven, that's why its in the plans. The reason is, an oven distributes its weight over a large area - unlike a screw driver.

I found that my vermiculite layer continued to get harder for about a week, although others have said theirs hardened up the day after the pour. How long ago did you pour your hearth?

One thing I would maybe do differently is to have an edge of cement round the vermiculite layer: I don't know how feasable that would be for you at this stage. But while the vermiculite does hold up the oven's weight very well, the edges can get a bit crumbly...

[RyH]

Thanks Frances, I poured the vermiculite on Tuesday evening, I must admit it is getting harder day by day.

When would you start to build the oven, wait a few more days or crack on now?

XJ - I will add photos over the weekend, not a lot to look at yet but coming on.

[dusty]

It will certainly hold your oven. Maybe the screwdriver thing was a bad example. It Is similar to strofoam, but much more dence and much harder. And the scrwdriver wouldn't be easy, but you could do it.

dusty

[Frances]

Ooops sorry, I missed that question... too late for advice now, but I think you could safely have started to build this weekend...

[gjbingham]

Four or so days is good before laying the floor of the oven, at least if the insulation layer feels firm. It really takes months to dry out completely, and probably only really happens when you cure the oven.