Concrete base direct on earth? Newbie Forum Discuss Concrete base direct on earth? in the Good Background Information forums; Hi, due to limited space, I am building my oven into an enbankment, directly off the back patio. This saves ...

[Stephen]

Hi, due to limited space, I am building my oven into an enbankment, directly off the back patio. This saves both space and time, but also means that the concrete base will likely sit directly on the earth, with a minor brick wall surround to support and contain the setting concrete. My issue is this : as the concrete is not suspended above the ground (like generic ovens), but will sit directly on the actual earth, I suspect it will be a bigger than usual heat sink. Should I therefore put some insulating layer (of what?) below the concrete base. Or simply make the insulating layer above the concrete thicker. Any suggestions would be welcome. We live in Melbourne Australia, so the climate can be cold in winter, so want to ensure the oven is as efficient as possible. Thanks for your advice.

[Rodneyf]

Steve , I would also be a little concerned about the amount of moisture that will be drawn up into your oven in times when you are not using your oven. Rising damp could be a problem if the area is damp. I don't see a problem with losing heat if you insulate properly, your insulation will only stop the heat leaving your oven and any heat that does escape will be absorbed through your slab and then through your soil.

[Stephen]

Thanks Rodney, Agree on the moisture. Spoke to someone today who suggested some drainage or blue metal below the concrete, to take the moisture away from the slab. I have also been assured that so long as i have enough insulation, heat loss should be ok. But moisture will be the main concern.

[dmun]

moisture will be the main concern.

Wet insulation is ineffective insulation. A moisture barrier may be in order. Also, if you have frost, a layer of well drained crushed rock will help prevent frost heave.

the concrete base will likely sit directly on the earth, with a minor brick wall surround to support and contain the setting concrete.

This retaining wall should be well supported, if it's bearing any of your oven's weight.