Help with laying the two-piece hearth

[jbarlow]

Hi
I am at the stage of laying the the structural and insulating hearth layers. Can anybody clarify whether the insulating layer is built immediately after the structural layer? Or should I wait until the concrete in the structural layer has gone off?
Thanks!

[james]

Re: Help with laying the two-piece hearth

You can do it either way. You can add either your vermiculite concrete layer or your solid state board insulation (FB Board, or similar) on top of wet concrete; or you can let your slab dry, and add the next layer on top of dry concrete.

Either way, you can leave the forms on the structural slab for quite a while, allowing the slab to cure.

Aren't we flexible? :-)

You can do it your way.
James

[JoeT62]

Re: Help with laying the two-piece hearth

I gave it a day - enough to "set" but not to cure. But James iscoreect. It really doesn't make a difference.

Incidentally, I wanted a smaller base of insulating "vermicu-crete" than the underlying slab as I wanted to drive my enclosure studs into the "real" concrete. I was able to remove an outer strip of "vermicu-crete" quite easily with a circular saw and chisel.

Good luck!

[james]

Re: Help with laying the two-piece hearth

...I wanted a smaller base of insulating "vermicu-crete" than the underlying slab as I wanted to drive my enclosure studs into the "real" concrete. I was able to remove an outer strip of "vermicu-crete" quite easily with a circular saw and chisel.

Good luck!

That's a very good point. The insulating layer only has to be as large as the cooking floor/dome of your oven. You can either:

1. Frame in the vermiculite layer to fit under the oven;
2. Cut your FB Board to fit under your oven; or
3. Cut back your vermiculite layer after you have poured it (alla JoeT62).

This might be an area where we can update the Pompeii Oven eBook to be more clear.
James

[JoeT62]

Re: Help with laying the two-piece hearth

I also used the vermicu-crete strips as insulation "filler" in the enclosure (still have the ceramic blanket and loose perlite, but maybe I needed to buy a little less perlite this way).

Of course those pieces of vermicu-crete are fun to play with. I freaked out my friend by tossing him one (they are LIGHT). Ahhhh....good times.