Inside of DPM Soaking Wet

[daveJL]

Hi all,

We are currently renovating a downstairs 1920 (ish) flat and have had damp proof membrane fitted by a local company. Plasterboards were then dot and dabbed onto the membrane and plastered.

The inside of the DPM is now soaking wet when you put your hand up the cavity between the DPM and plasterboard. Wet patches are present on the floor around the edges of the affected areas where moisture is running down the DPM.

We've also got some mould growing around the unplastered bottom edges of the plasterboards and some small spots up the walls as well. DPM is full height in the kitchen (I thought this was overkill but its the damp companies guarantee and that's what they said to do so we rolled with it) and half height in other spots.

Video I took of the problem today:

*Can't post a link but it's vimeo(dot)com/397689558 - just replace the (dot) with an actual . to view.

The property is of brick construction, two layers thick with no cavity between them. The DPM has been drilled into the internal brick.

My theory is that the DPM is cold as there's no insulation in the walls therefore condensation from water vapour inside the property is forming on the DPM as it can't move through the wall and get out. The DPM is effectively keeping moisture in as well as keeping it out.

Just to be clear the construction is as follows:

External Brick
Internal Brick
DPM
Platerboard (dot dabbed so a cavity is formed)
Plaster

Has anyone encountered this problem before? Can anyone suggest a fix?

FWIW we have retro-fitted trickle vents and added pacifier vents but the problem remains (although condensation from windows has ceased and relative humidity is at a normal level (35-50%).

I'm feeling like we need to add some kind of insulation. Which means all the boards will have to come off and maybe even the DPM?

Not sure where to go on this one so any help much appreciated.

Cheers

Dave

[aeromech3]

Do you know what DPM was used, appears to me as a DIY, that a semi permeable vapour barrier might have been a better choice and at any rate a cavity for venting draining was needed between the brick and DPM / barrier, not plasterboard and a DPM.
Gather more opinions please.

[wes56]

davejl do you still want help