Damp soil / concrete under floorboards

dominoman

We are buying a late Victorian house which has damp under the suspended floorboards. It has caused problems in the past as all the floorboards were replaced around 40 years ago, and are now rotten enough to need replacing again.

I want to fix the underlying problem of the damp.

When I crawled under the floorboards the ground was damp enough that the concrete oversite layer that the internal walls are supported by was crumbling in places. I was able to dig into it with bare hands.

What can I do? I was thinking to lay a plastic membrane and then pour concrete or shingle over the top. But to do that means lifting all the boards. It also isn't easy as I'd need to go around all the internal floor supports.

I really don't want to have to lay new foundations (like underpinning) if it can be avoided.

Any ideas on what to do? Thanks in advance for any advice!

zaax

there is another tread about this sort of problem - how far are the air bricks off the ground

wallbash

Having bought an old house with rotten floorboards, I ripped them all out, filled void with rubble, sand on top, plastic membrane and then concrete on top. This had a layer of painted DPM applied. This I did all with help, but all of an amateur sort. Then I got in the professionals to top screed.

It was not expensive and not difficult, but did take time.
It certainly cured all damp problems.