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RyanCD 07-17-2006 07:42 AM

Foundation Slab
Yesterday I poured the foundation slab for the Pompeii Oven. I want the overall oven in the end to be 36".

Anyway, I poured the slab 45" x 4'. It is going to be integrated into a kitchen outdoor island that we poured the foundation for yesterday that is shaped as an "L" and the oven is going to be in the elbow of the "L". Do you think this slab is much to small? Or do you think I can leave it as is and just make sure when I pour the base of the oven that that is a bit larger or will it not be safe?

If you click the link below you will be able to see what we have done to get a better idea.

Pizza Oven Foundation

Fio 07-17-2006 08:50 AM

It's way too small.
You're leaving no room to account for the insulation or covering on the dome.

It should be at least 6 feet wide by 8 feet deep. Otherwise, you've got no room for the insulation, landing, vent or door.

I just completed building a 35" oven. My slab was 60 X 72. I wish I had gone bigger.

Before you get too far along, enlarge your slab.

dmun 07-17-2006 09:30 AM

reduced base size
I don't know how you are going to finish the oven, but there is no particular reason you couldn't use your base as a pedestal, and pour a larger hearth slab on top of it. This would reduce your firewood storage, but not by much.

After all, much of the weight is in the center of the slab, not at the edge unless you build a massive enclosure.

RyanCD 07-17-2006 10:15 AM

Dmun, Thank you that is exactly what I was wondering. I am so relieved to hear that most of the weight is set on the center.

Thanks again!

james 07-17-2006 10:18 AM

Stand size
Hello Ryan,

Putting a 36" (internal) oven on a 45"x48" stand won't fit.

Counting sideways you have roughly:

36" oven
9" oven walls
10" insulation
2" enclosure walls

57" wide

You can tinker with that by minimizing your oven wall width, using more efficient insulation (all Insulfrax for example), and making thin upper walls. Or as David noted, you can cantilever your hearth slab. But fundamentally, you need each of these functions.

Once you have your oven footprint done, you can add other outdoor kitchen elements with either block or metal stud "cabintets".

There is posting on stand size that might help.

RyanCD 07-17-2006 10:31 AM

I understand that the oven itself won't fit with all the layers going into it, but this base is just to store wood and later on I will put a larger slab on it once built up. I just was wondering when I start constructing this if this base can support a larger slab (the hearth foundation) which will be the correct dimensions. My only question is will this base be strong enough to support a larger base about 3 feet in the air supported by the cinder blocks and obvioulsy rebar in the second slab. I want the pedastal part of the oven (where I am storing the wood to burn) to be smaller. so it it cohesive with the island as a whole. I pretty much am looking for in the end to see the kitchen island with a large box sitting on the "elbow" of the "L".

Dmun explained just what I needed by telling me that the weight sits primarily in the middle.

james 07-17-2006 03:52 PM

Yep, I think you are fine. You will cantilever the hearth over the stand on both sides, but with a rebar slab, you can span that distance. That, and as David noted, most of oven weight will be over the stand --it's the insulation layers and the enclosure wall that are at the outer edge of the hearth.

RyanCD 07-18-2006 02:34 PM

Wonderful thank you everyone for your help!

RyanCD 07-18-2006 02:42 PM

Oops one more question! For the hearth base, which will be roughly 77" x 86", and the situation I am with the edges airborne, how many pieces of rebar should I put into the slab? Any suggestions you have will be greatly appreciated.

dmun 07-18-2006 06:28 PM


Originally Posted by RyanCD
Oops one more question! For the hearth base, which will be roughly 77" x 86", and the situation I am with the edges airborne, how many pieces of rebar should I put into the slab? Any suggestions you have will be greatly appreciated.

Here's what the instructions propose:

Originally Posted by FB Pompeii instructions
Lay a grid of 1/2" rebar slightly shorter than the external dimension of the wood forms, on 12" centers, starting 6" in from the edges of the form, directly on the concrete. This will set your rebar roughly halfway inside the concrete pad, enabling it to hold up your oven across the opening of the stand (Photo 6).

That's what I plan to do, 12 inches apart, six inches in from the end, the grid tied together with wire ties.

Just keep the rebar away from the edge. Rust can stain the concrete, and eventually bust up the slab.

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