Damp Sub-Floor Non Cavity Wall 1930's semi

3 Mar 2008
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United Kingdom
I have just discovered the reason for the musty smell in my spare room

Skirting board is rotten and there is damp behind it
The room is on a downstairs wall
Its a 1930's semi - not cavity wall

The floor used to be the kitchen floor so its concrete underneath
I Installed a hardwood floor on top
making sure that there was a damp proof plastic sheet underneath the concreate area

The skirting board is rotten and there is some mould about an inch or 2 above the skirting board

Any help appreciated
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Suspiciously similar to something we had a while back in our 1850s house.

Concrete floor was on the lower ground floor and we had a membrane over it and underlay/laminate as the floor covering.

Damp walls and rotting skirting around the chimney breast and wall opposite made us realise that the DPM was directing water elsewhere other than up through the floor. We lifted the floor and it was clear the concrete was damp from the colour of it! A few days later it was dry again.

We also opened a bricked up cupboard under stairs and took the concrete floor up to reveal rotten joists and no DPM under the concrete. We have patched temporarily and used seagrass floor cover as we don't want to have to adhere to new building regs when repairing as it means digging way down.

I would bet you have the same builders who put concrete down over the old floor but didn't put anything underneath and therefore allowed damp to rise up over time.

One potential solution is to use a liquid DPC on the concrete, extend to walls then re-level floor as per another thread. If we had known that is the course that we could have taken.
damp in a solid 1930's floor that used to be a kitchen?

50p says the old water main is laid in that floor, and is leaking.

It may well be an iron pipe that has gone through, and it may well be at the elbow where it turns up to come through the floor

If your other floors are wooden, get under and see if the pipe is visible, and if you can bypass the part in the floor.

You can usually hear a faint hiss from a leaky mains water pipe, that will go when the outside stopcock is shut.

You can also test for it with a tumbler of water. Rather than try to describe how to do it I will see if I can find a previous post.

here it is

Thanks to ChrisR


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