I am building a pizza oven and kitchen area in my garden. I am trying to work out if there is a specific type of concrete I need.

My question is only about the concrete slab (the foundation). The slab will be approx 2m x 2m

My calculation for the weight (that the concrete slab needs to support) are

Dense bricks: 70 * 18.2kg = 1,274kg
Concrete slabs: 13 * 15kg = 195kg
Pizza oven: 1 * 50kg = 50kg

Total: 1,519kg

How do I determine what type of concrete to use? Would general purpose suffice?

  • The oven itself (the part that gets hot) should not be made out of concrete - really bad material for that. The "frame"... that's a different story and I am sure you can get a few good opinions here. – DMoore Mar 15 at 17:28
  • 2
    I think the question is about the slab the bricks will land on. For which "regular concrete" is probably fine, but will be much finer with steel reinforcing bars embedded in it. My observation that you can ignore is that most people I know who have built a high-mass oven at home hardly ever use it, and if you are still at the "planning the slab for it to sit on" stage you could change to a low-mass, highly insulated "rocket" oven that consumes much less fuel and time to become ready to bake in. So you might actually use it more... – Ecnerwal Mar 15 at 17:34
  • Yeah it is. I updated my question to make it clearer. (if it matters, the oven is white portland cement and perlite and water (2:5:2 ratio) – MyDaftQuestions Mar 15 at 17:34
  • Updated... 2x2m (not sure how deep it needs to be) – MyDaftQuestions Mar 15 at 17:46

The slab loading (pressure over area) is trivial - you have 4 square meters to carry 1600 kilos (rounding up) which is pretty much nothing for any grade of concrete.

The more important function is spreading that load (plus the mass of the slab itself) across the soil, but that's still a very low loading (roughly 4 KPa, plus the slab (at roughly another 1000 kg, so perhaps 7 kPa total), if I have my SI units straight) while concrete compressive strength is 15 MPa at the low end. Clay soil bearing is about 70 kPa and other soils bear more.

A 100-110mm thick slab is probably plenty thick, and gives the 50mm concrete cover your reinforcing steel should have for corrosion resistance.

What is under the slab and your local climate may add other constraints, such as footings for frost movement resistance (or not.)

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