Damp concrete floor in extension, tiles breaking

phil24_7

Or perhaps PAY for a damp survey from an accredited professional and then follow their advice?

You are basically saying that you will gladly hide a problem again in future. Do you know how much damage can be done to a wet wall if the water in it freezes? Put a bottle of drink in the freezer for an idea!

Be careful digging through the floor slab. If there is a dpm it could very well be damaged meaning it would then become useless!

Your best bet is to 'carefully' dig away at an edge to see if there is a dpm upstand around the perimeter of the room and/or excavate around the outside to see get to the bottom of the slab (this depends how the extension was built) to see if one is installed. This wont however tell you what condition it is in under the slab. If the ground wasn't properly prepared then there could well be damage to the DPM.

TranceNRG

No I'm saying if there's no obvious cause for the damp and the walls were wet from a leak before, then I would hack off plaster and re-plaster rather than waiting a year for it to dry out.

What if there's no DPM or even if there's one, it's impossible to tell if it's damaged or not right?

If it's found to be one of these (can't see any obvious leaks), could there be problems down the track by adding a water proof membrane and re tiling the floor?

phil24_7

Its not the best way to do it but concrete on the ground as a floor doesn't usually suffer freeze/thaw so should survive being damp.

It's worth investigating things so that you know where you are. Blindly attacking things with unsuitable remedies could cause you more problems further down the line.

You need to find out where this damp (and any future damp) is coming from before deciding on a course of action.

TranceNRG

I do want to investigate it that's why I've been asking around what the best way to tackle this is. I can pay a surveyor to come and give me his opinion but I'm worried he's not going to tell me more than I already know. I think the best thing to do now is to make sure it's not leaking from the pipes in the wall next to it and it's not leaking from the toilet next to it. If it's neither of them then yes I'll look in to getting a surveyor.

Doozergirl

The problem is near enough obvious.

You have a wet floor from a previous leak compounded by a breached DPC which has only just been partially addressed by means of a french drain. The floor has never had an opportunity to dry out because it has still been soaking from outside too and the damp has affected the tiling in the manor wet spot.

In exactly the same way that the walls were still damp because of the ongoing breach, you addressed the symptoms on the wall but not the cause, hence the floor is still symptomatic. Rendering the walls has done nothing to stop the damp, it has covered it. It cannot penetrate the internal render.

Of course it's possible that there is an actual leak from a pipe but I think it would show much more as water and saturating in that area, not a general dampness.