MarkBentley

This is a response from a company that does insulated raft slabs, about @Iceverge's idea about a timber insulated raft foundation:

With being 30m2 or less we are hoping to do this via permitted development and therefore not have to adhere strictly to building regs. I'd not heard of rubble trench foundations - that could be a viable option

That seems like a sound idea. I'll look into it a bit more. Thanks

We are building a 30m2 timberframe single storey annex and want to minimise our use of concrete. We want to include a wet underfloor heating system. For the flooring we are thinking the layers would be: compacted ballast compacted sand PIR insulation board UFH pipes screed wooden flooring Thinking that we don't need a concrete slab for stability because if it shifts a little and the screed cracks the wooden flooring will cover over those defects. The question is how to constrain the flooring? Can you use blocks without foundations, but supported by earth on the external side, to create the footprint of the building and then compact and build up the flooring within the fooprint? The timberframe structure can be supported by ground screws. All the examples of using ground screws that I've seen have the building suspended slightly above the ground - is that essential? Can you position the ground screws so that the base of the timber frame sits ontop of the footprint blocks but the weight is supported by the ground screws? Is there a better way to combine a single storey timberframe build with a solid floor whilst still using minimal concrete?

Looking to build a 30m2 annex in the garden for multipurpose use: Home office and extra living space Housing of offspring who refuse to leave the nest Maybe even Air BNB