Mark S. wrote:
The floor was breaking up when I'd taken the carpets and lino up. The
top inch or so was hollow and crumbling and lifting off.

I took the this top inch off over the whole downstairs floor.

There's a concrete slab underneath except between the two was the
bitumen type stuff which is what was the damp course.

Is the floor slab a) coherent and b) flat and reasonably smooth?


I used self levelling compound over the whole floor to keep the dust
down and make it less of a pain to keep swept etc.

Bits of this have lifted off leaving the salt deposits under them. If
you put something on the floor and leave it there's a "damp" patch
under it when you move it.

Probably the damp-proofing was breached when you removed the screed.


Do I repaint the floor with a bitumen paint and will that fix it or
just dig the whole lot out and re-lay it in the normal way with proper
layers, insulation etc.

I'd be inclined to remove the top (again), hire a multi-headed concrete
floor scabbler, run that along, clean up, apply bitumen emulsion "as
it says on the tin", and re-screed.

How long did the previous job last, I wonder? 50 years?