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OK interesting idea so don't take this at face value, but I'm interested why this isn't done more.
I was watching a video about a passive house where they laid thick polystyrene on a base, then poured a massive reinforced raft on top and built off that to avoid any thermal bridge at the base of the wall.
Today I was looking up the compressive strength of normal clay soil compared with celotex. Seems they could both be around 0.15N/mm².
So my question is why wouldn't you dig out to 1m or whatever, fill to 250mm below the top of your required foundation, chuck 100mm celotex on joined with both the floor and wall insulation, another 150mm of concrete and then start building as normal?
Sounds like a massive faff on face value but I'd be interested whether this kind of modified trench fill would have been easier/better than building an engineered raft on polystyrene.
I was watching a video about a passive house where they laid thick polystyrene on a base, then poured a massive reinforced raft on top and built off that to avoid any thermal bridge at the base of the wall.
Today I was looking up the compressive strength of normal clay soil compared with celotex. Seems they could both be around 0.15N/mm².
So my question is why wouldn't you dig out to 1m or whatever, fill to 250mm below the top of your required foundation, chuck 100mm celotex on joined with both the floor and wall insulation, another 150mm of concrete and then start building as normal?
Sounds like a massive faff on face value but I'd be interested whether this kind of modified trench fill would have been easier/better than building an engineered raft on polystyrene.