Waterproof & Heatproof Firepit Material?

[pauls]

Hello,

I would like to build an uncovered pit in my garden for BBQ-ing (with sloping sides to reflect heat out).

What material could I use for the base and sides?

It must not fracture under heat, or absorb water (which may turn to steam).

Steel is an obvious choice, but rather unattractive, and may warp with heat.

I imagine firebricks would absorb rainwater, which could cause them to crack/explode when heated?

How about marble, granite, concrete, or terracotta tiles?

Any suggestions appreciated - I realise this isn't really an oven, but this seemed like a good place to expect an answer.

Thanks,

Paul.

[DuncanM]

Concrete, unless a special blend, doesn't cope well with direct exposure to heat, so I wouldn't use it.
I think out of granite and marble, granite would be far superior, but it's also possibly worth considering soapstone.
Firebricks do absorb water, but it wouldn't take too long for the steam to evaporate (depending on thickness of the bricks). I've regularly used firebricks (standard sized house bricks) as a ring for numerous huge bonfires in my garden. There's never, ever been any cracking (after ~4 years of constant exposure to the elements and 20 bonfires/campfires at a minimum a year). I can highly recommend them.
Steel would be a good one too, to counter the warping, use a decent graded and thick steel.
Got any rough sketches of what you want your barbie to look like?

[pauls]

Thanks for your advice Duncan.

Hopefully this sketch gives the basic idea of what I have in mind.

It would be sunk into the lawn with the top edge sticking up about 2-3 inches.

Coals are along the bottom, so it will be hottest directly above, and cooler at the sides.

Hopefully the two sloping sides will reflect heat out at people sat around.

Four sloping sides would be even better, but might be beyond my construction capability.

[pauls]

Here is one showing the lawn.

My original idea was to use concrete paving slabs, but it doesn't sound as though that would be a good idea.

[downunderdave]

Another alternative is to use castable refractory. Whatever material you use you probably should attend to the drainage under the thing so it doesn't sit in damp soil. You could have a few inches of crushed aggregate over some agricultural drainage pipes. but probably better to have the whole thing above ground level.