Filling sub floor void with concrete

[Steveb21]

I have a wooden subfloor in my 1950s bungalow - hate the cold drafty floor!

I have some work starting soon for an extension and will have a vast amount of soil which i will need to dispose of. I am thinking I could use some of the soil to fill the existing subfloor to get up to a level to install a concrete slab.

Currently not sure how much of a void i have but if i >

Top up with soil > Grade 1 > Sand > DPM > Concrete > Insulation > Vapour Barrier > UFH > Screed

Thoughts?

Other options is to insulate between the joists with celotex or mineral wool

 

[KenGMac]

Steveb21, good evening

How much "crawl space" is there under the floor?

Problem with infill is that you would really need to lift if nit all, certainly a lot of the floor, in your list of what is needed, you should add compaction of the reclaimed soil, and the Type 1

it will be faster, and easier to insulate between the joists, provided there is a decent crawl space.

Ken.