Damp sub floor

[Kevin]

I have had some floor boards up to run some new aerial cable. I noticed that up again the party wall there is evidence of damp in the concrete floor, that is the floor against the ground not the floor of the room. This is well below the DPC so no real concern at the moment. I am only concerned where it is coming from. The water table is very low where I live. There is a rainwater down pipe at the boundary on the neighbours side. I can see that the down pipe is not leaking above ground but I was wondering if there was a below ground leak of may be the soak away is blocked and water is backing up.

Kevin

[stuart noble]

I have known two instances where tiny leaks in the mains supply had caused a fine spray to travel a good couple of metres. No sound and only detectable by touch. Just a thought

[harryagain]

You may be right. You also need to make sure that the void below the floorboards is ventilated. Humidity can cause rot in the floorboards.

[Kevin]

You may be right. You also need to make sure that the void below the floorboards is ventilated. Humidity can cause rot in the floorboards.

My side has a single story extension on it but is otherwise well ventilated. There is no apparent damp except you can see it just where the floor joins the wall. I will have to check with the neighbour. He has a conservatory on the back.