Construction Suggestion

[iluvpizza]

Hi everybody, I am building a Pompeii 42 inches in my backyard.
I am building it already elevated from ground level since it is on the ground around my brick patio (see pic). For this reason I am not going up more than 1 round of cinderblocks and I am planning to put the heart slab (one layer of concrete and one insulation layer of Vermiculite) on top of if.

Now since there is not opening in the front, I would like to fill up the space under the slab but I do not want to do it with concrete (too much mixing , weight, costs, time etc.) so I was thinking of sand and glass.
I was thinking of this as a quick solution that also would insulate in some way the heart slab from the base one (for the oven then I will have the Vermiculite).

What do you all think? Any other ideas?

[Tonyp]

Re: Construction Suggestion

I don't see any reason to need to insulate between the base and the hearth between the blocks. I do think you will need to put something in there to support the hearth when you do the pour since you can't temporarily brace it from below. Perlcrete? More blocks in the shape of a #or + ? Or just fill up most of the space with block? If so I wouldn't bother to core fill them or anything..

[stonecutter]

Re: Construction Suggestion

If you go the loose fill route, place it in the cavity so that it won't settle.Don't use anything with fines, and you should add a couple weeps just in case. Fill the core with broken brick, rip rap or any large aggregate.

[ATK406]

Re: Construction Suggestion

Hello Pizza Lover,
Congratulations on starting your journey. I see that you have already boxed in your base (i.e. there is no opening). I would encourage you to consider opening it back up. Even if it is shallow, the pocket underneath the hearth would be a handy place to put your tools (brushes, scrapers, gloves etc.). You could even make a drop down door (hinged at the bottom) or a drawer to protect it from the elements. Not trying to interrupt your own creative vision, just pointing out from a practical standpoint, a place to put stuff out of the way can be very useful.

Besides that, a couple more cinder blocks underneath the support slab would be enough to support the bottom of your form while the cement cures. There is no need to insulate the underside of the slab - as the slab itself is a pretty massive heat sink and reducing the heat loss from it is a waste of time. The place to apply insulation is between your firebrick (which should be hot! hot!) and your support slab which you would like to keep cool (or merely warm). If you are heating your slab to the point where heat loss from it to the environments is a concern, you have lost the war already.

Sorry for the lengthy post. Good luck on the rest of your build, however you decide to proceed.

Regards,
AT

[iluvpizza]

Re: Construction Suggestion

Thanks for your answers, I think I will fill it up placing cinderblocks on the side (where there is no hole) so I can build the heart slab on a flat surface.

[karl]

Re: Construction Suggestion

I think you can do this very simple. Fill it with sand until 10 cm from the top. Then lay 10 cm thick aerated/porous concrete blocks and you will have a nice insulated flat plattform for your oven build.

karl