Damp Patches After DPC Injection & Plastering Damp can be a major issue in the home. Find answers to questions or post your own here.

[acidburn110]

Hi! First post on here and its a miserable one i'm afraid.

We've bought and live in a late Victorian terrace (1900). There hadn't been a damp course until we moved in in November, but there is a chemical one now. Our plasterers dotted and dabbed over where the old plaster had been hacked off and redid the render outside.

After a couple of weeks, we noticed saucer sized damp patches on the plasterboards, particularly towards the back of the house. Not so bad in the dining room, but spreading, meeting and rising up from the new skirting in the kitchen (the most exterior room). Rather unfortunate as we'd had the skim done in there and lobbed a coat of Eclipse paint on once that had dried.

The DPC company tell us that the DPC has been bridged externally as the render now covered that level. Internally, we were told that the fact they'd dotted and dabbed boards instead of using lime and the supplied additive had allowed the damp to travel up and into the boards. The plasterer is coming to inspect the problems tomorrow, so i'll report back then with his ideas. In the meantime - what do you lot think? Feel free to ask anything further which you feel may be pertinent.

[stoneyboy]

acidburn110,
Your plasterers should have applied a coat of concrete render up to about 1m. Plasterboard is absolutely useless.
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[acidburn110]

Cheers Stoneyboy.

All old plaster - off. Concrete / new skim - on.

So far, so good; but will the concrete actually prevent the damp from coming though? Hypothetically speaking - if it doesn't, what other course of action is there to take?

[stoneyboy]

acidburn110,
Hopefully a waterproofing agent was added to the concrete render mix and this should limit damp ingress. Accept that there will be some dampness and use a paint which will allow the wall to dry out through it. I use Dulux supermatt but don't forget to thin the first coat.
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[acidburn110]

After the recent and ongoing wet weather, we seem to have damp patches again! Living room, dining room and kitchen (under the window AND on the internal wall). All seems sound with the window frames and all around, brickwork etc. Some degradation to the pointing but nothing serious.

I accept that nothing is ever going to be bone dry, but as all recommended plastering specs have been undertaken - should we really be having such issues at this stage?

[stoneyboy]

acidburn110,
Were you able to check the mix used - it should have been 3 or 4 sharp sand to 1 cement. Weaker than this and the render becomes more and more porous.
If the render coat is still exposed try throwing some water on it, it should not be adsorbed.
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[acidburn110]

I personally was not able to check this. However the plasterer has been used by our family since the 1970's and is, we hope somewhat reliable.

A further update. No damp patches have reappeared as yet, but there appears to be one, long, straight patch of effloresence underneath the kitchen wall. Almost as if it's been poured on. Should i sand this back, treat with neutraliser and repaint?