Hole in concrete living room floor

[DazaW]

I have just lifted some laminate floor in the corner of my living room, which I laid 10 years ago, and found the underlay to be damp.

The floor is soft and crumbly and using just my hand I have dug down about 120mm and can start to feel the edge of some old dpm around the side.

This is in the original gas meter location which the previous owners moved when extending, so it seems they just filled the hole in without adding a dpm.

I need to stop it being damp so what is the best course of action?

i'm thinking: (i) dig wider to find the edges of the old dpm, (ii) compact down some sand/cement under, (iii) add new piece of dpm overlapping old as far as possible, (iv) screed on top?

How thick should I add in one go?

 

[foxhole]

If the floor is concrete you would expect underlay to be damp as concrete sweats as it absorbs and releases moisture from the room.

 

[DazaW]

It's an isolated problem. The rest of the floor is dry and this is definitely a hole that's been filled in in the past and dpm compromised.

 

[bobasd]

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