Insulated firebox thickness

[Wiltshire_chris]

Hi folks, I've built a few offsets now and the next one is going to be trailer mounted 500 litre for me to use for pop ups and fetes etc. The one I'm building at the moment is having a insulated firebox. It's a200 litre compressor reciever (propane tanks are hard to come by in the UK) with a 4mm fire box then 25mm of ceramic insulation then 1.5mm steel sheet folder to cover the insulation on the 2 sides and the top. So my question is what is the minimum acceptable thickness to make a insulated firebox out of. In the ideal world I'd use 10mm but short of a remortgage that ain't gonna happen.

[Dirtytires]

For any firebox, 0.25" seems to be the gold standard tho you can go thinner if you want. Anything thinner than 0.125 is going to have a pretty short life. Obviously, the outer skin just needs to be thick enough to resist dings and hold the insulation in.

Sorry, you will need to convert to metric.