Note - I've read Should I insulate my pizza oven between the firebrick base and concrete? and Will a slab poured with mortar stand up to service under a pizza oven? but they aren't rerally what I need. Strength isn't the issue, heat transmission is the concern here.

I have just poured a heavy duty retaining wall in the back garden. It's really heavy duty, due to soil/slope issues - about 500mm wide at the base tapering to 250mm at 800mm height. It contains steel reinforcement, and is faced by expanded metal (EML) + render on the patio side.

The concrete used was professionally placed and is C40 grade (UK - a mix with much more cement powder than usual, approaching 500kg per m^3). It was low water and used superplasticisers and a higher proportion of sand/fine aggregates, instead - i.e. a self compacting/self consolidating mix.

The wall has a right angle corner, and we have now decided we want to put a steel tray for a briquette BBQ or pizza oven in that corner. To do it, we plan to pour 500x500 mm concrete in the inside of that corner, to create a total 700x700 mm flat concrete surface for use.

My concern is the intense heat of a BBQ or oven resting on this concrete. Especially with steel in its structure, and cycling over time. I dont want any issues. I could just airgap it and have a 5mm steel tray resting on a couple of rows of firebricks, it probably won't move due to weight. But I'm not convinced about safety and heat issues. I want long lifetime too, and ideally no movement or maintenance.

If I want to have it resting directly on the corner of the wall, perhaps on some kind of mortar bed or insulation layer, is there a specific insulating material one uses to stop heat conduction through the fabric damaging what it's resting on? Rockwool or something else with extremely low conductivity?

What should I do, and what's the risk of damage or weakening over time?

  • Doubt very much if you have to worry about damage to concrete. Maybe from an oxy-acetine torch held to one small area(if moisture in cement). Be more concern about using extra fuel to heat oven and concrete. concrete is good heat sink, so might want insulation to keep heat to the oven.
    – crip659
    Nov 24, 2021 at 23:10


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