We've recently (6 months ago) moved into the ground floor flat in a tenement, about 120 years old. We had some damp proofing about 4 months ago and the affected walls now seem fine.
However, about a month ago we started noticing a musty smell in parts of the kitchen (no damp work was carried out on the walls here, but we have had a bathroom re-fit in the room adjacent to the kitchen, about 3 moths ago). The floorboards are exposed and sealed in the entire flat but we had put a rug down in the kitchen which also seemed to have picked up the smell. After a little investigating (crawling on all fours sniffing floorboards) the smell seems to come from where the floorboards meet the wall (adjacent to the bathroom), and also from between the floorboards in a small area (about 1.5 metres away from the wall next to the bathroom so maybe there's no connection??).
We lifted a small section of boards which were loose and a quick check under the boards revealed about a 3ft drop, and no visible signs of dampness. The musty smell was pretty strong down there.
Could it be dry-rot?
As we've just had damp work we know these guys can be expensive so we're wondering if there's any further measures we can take before calling in the professionals?!

Thanks for any advice!

Lisa and Mike

I agree with CW, the first thing to check is that there is adequate ventilation under the floor.