Concrete/Screed under damp floorboards

CrispyPancake

We've just found an issue with our house, after cleaning the carpets there was a strong odour that remained so we pulled back the carpet and underlay and found the floorboards were rotten. Underneath the floorboards we expected to find joists but instead (as in the picture, one completely rotten one has been almost ripped out!) there is what appears to be some kind of concrete or screed. The house was originally constructed in the 1930s, but we don't know what happened with the flooring.

Any idea why this would have been done? And what the likely solution could be? We've got someone we know and trust to look at it but just wondering if anyone had any good guesses?

grumbler

For some reason this type of floor (with tiles, not boards) was typical for kitchens - cold concrete slab on wet soil without proper water proofing (they simply didn't have good materials for this) and heat insulation.  If it's not kitchen now then, possibly, the layout was changed at some point. 
The simplest solution could be replacing this bitumen mix with some modern membrane (+underlay to protect the membrane?). 
The best yet expensive solution is to brake the slab, remove the soil underneath and make proper suspended floor (joists or beam&block).
Intermediate solution - new slab at lower level, insulation and membrane, screed.

stuart45

How much do you want to spend on putting it right?

CrispyPancake

grumbler said:

For some reason this type of floor (with tiles, not boards) was typical for kitchens - cold concrete slab on wet soil without proper water proofing (they simply didn't have good materials for this) and heat insulation.  If it's not kitchen now then, possibly, the layout was changed at some point. 
The simplest solution could be replacing this bitumen mix with some modern membrane (+underlay to protect the membrane?). 
The best yet expensive solution is to brake the slab, remove the soil underneath and make proper suspended floor (joists or beam&block).
Intermediate solution - new slab at lower level, insulation and membrane, screed.

AHH. Thanks for that, very helpful information. Not quite sure what our builder friend has recommended as he spoke with my partner but from what she said on the phone it sounds like the intermediate solution.

Imagine it's going to be pricey but what the hey. *Grimaces*