Low depth insulated floor options for basement.

[ringi]

I have a basement where I need to insulate and waterproof the floor. I don’t have enough head height to build up the current floor, and the “foundations� for the external walls are only about two brick depths below the top of the current floor.

The soil is free draining clean sand down to a good depth and the property is on a hill with ground level at the back about the same as the basement floor level. The ground then slopes away past the boundary of the property. (For people that know the area the property is in Heaton Norris.)

Can anyone think of a floor system that will avoid the need to big much out, and hence having to underpin the walls?

For example using stronger concrete so slab can be thinner or even floor insulation that is strong enough to be laid directly on the sand, with a drainage membrane above, then a boarded floor.

(I have a Structural Eng coming round in 2 weeks time to advice on a loft conversion, hence the test pits in the basement to find out the foundation depths. I will ask his advice at the time, but would like to know about any options that would avoid having to underpin walls.)

[lutonlagerlout]

if the basement is going to be made habitable you will need calcs and building regs
LLL

[ringi]

This basement has been used as a flat from the 1990s or before, so it is already classed as habitable.

The tanking has clearly failed on one wall, other walls show signs of dump but may just be condensation and the floors have no insulation, therefore they are getting lots of condensation. I could just do it all as repairs so avoid most building regs, or do a good job.

It will all come down the costs of different options.

I understand how to sort the walls out; I just can’t work out what can be done to the floors without hitting the cost of underpinning.