I've just had damp proofing work done to the ground floor of my house (1920s mid terrace).
However, when they rolled the carpet back they found the underlay was damp and beneath that the floor slab was damp. They said it was not a concrete floor slab but some unknown material that sounded light and hollow.
Any ideas what material that could be?
How expensive would it be to replace it?
Thanks in advance for any advice, I'm clueless!