Damp / wet concrete floor

Talon.ie · 25-10-2023 05:08PM #1

I had to lift a carpet in a rarely used ground floor bedroom the other day. The underlay was a little damp under it and when I lifted the underlay the concrete underneath was wet.

There doesn't seem to be any obvious leak and the walls are dry, so no rising damp. There's also a damp proof course in place.

The house is a detached dormer and was built in the late 80's

A quick google says I really have 2 options

1, Dig up the floor and add a new damp proof membrane (sounds expensive)

2, Add a surface damp proof coating (i.e. some kind of paint on sealer)

What should I be looking into here before I go trying any kind of DIY job? Or is this a case of getting a builder in to have a look

Madd002 · 25-10-2023 06:54PM

Husband said there's a leak, prob pipe going to radiator as originally it would go straight across under floor and into a T to connect to other rooms

hydrus21 · 26-10-2023 07:57AM

A house built in the 80's should have a plastic floor membrane but could have been punctured during construction.

If you had a leaking pipe I would expect damp to be rising up the walls in places but you need to eliminate a pipe leak first.

Is your heating expansion tank constatly filling slowly? Or if a sealed system, are you loosing pressure?

If the damp is coming from the floor then 2/3 coats of bitumastic paint (Synthaproof or Blackjack) will do the job.

Calahonda52 · 26-10-2023 08:13AM

https://www.boards.ie/discussion/comment/121285017#Comment_121285017

Not the best idea as its not addressing the issue, will only shove the wet elsewhere, walls etc

As noted where are the heating pipes? , if gun-barrel in a 80's house then close to end of life

hydrus21 · 26-10-2023 08:42AM

https://www.boards.ie/discussion/comment/121285042#Comment_121285042

Common practice to use bitumastic paint as a floor membrane back in the day. Also Marley vinyl tiles on bitumen or clay tiles on a cement mix.

10-10-20 · 26-10-2023 09:00AM

Just as an example of an underfloor leak:

https://www.youtube.com/watch?v=p57T_qLQM-A

So try and work out whether you have a leak from the central heating or off the water supply. Locate where pipes may be and start working out potential causes.

Talon.ie · 26-10-2023 02:52PM

I'm thinking it may not be a leak. The damp patch is in an corner of 2 exterior walls. And there's no rads on one of the walls. The most logical path for the pipes to run doesn't go past where the damp is.

I'll take a closer / better look once I get the rest of the carpet up just in case there's more damp areas.

Calahonda52 · 26-10-2023 06:22PM

https://www.boards.ie/discussion/comment/121286668#Comment_121286668

Check your gutters.

DO you have a patio outside that is above the DPC?

Damp / wet concrete floor

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