Originally posted by Kris S
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It depends somewhat on the soil you are laying your concrete foundation slab on to, but yes generally you need to compact it with some aggregate first.
I don't like those thin 100mm solid blocks, give them a decent push and you'd be able to knock them down. However for the size of your oven I think the 150mm wide hollow blocks are sufficient, no need to go to the wider 200m blocks. By filling the cores with concrete you tie the blocks together and produce enormous strength especially if some steel bar is used as well.
The big advantage of the enclosure is that you don't have the issues of drying verm/perlcrete insulation. The enclosure can be filled with dry loose perlite or vermiculite over the blanket.
It is generally recommended that a 5:1 vermicrete be used for the underfloor insulation. Anything leaner is not considered strong enough to take the weight of the over sitting on top of it. The mix over the dome however is better at a 10:1 mix as anything richer is a poorer insulator (if doing an enclosure you don't need a a wet mix over the blanket)
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