Black Mould and Paint Bubbling due to Condensation

Postby ahmurray » Mon Jan 28, 2008 10:25 am

Greetings, all.

I'm after some advice about a problem in the bedroom (not of a Deleted nature, I hasten to add!)

The previous owner of our house rather unwisely turned the fourth bedroom into an en-suite, with just an open arch through into the main bedroom.

As a result, we have had a recurrent problem with condensation and paint problems which we can't seem to get rid of, despite fitting an extractor fan.

We redecoratated a few years back, but the black mould keeps coming back, but more worringly, we have recently seen that the paint has blistered and bubbled in places. This isn't what I would expect when paint gets damp and flakes off, it is more like a chemical reaction in the paint. The bubbling is solid with nasty brown and yellow stains around it.

At the weekend I attacked the black mould with HG Mould Spray which worked superbly, not a sign of it left, but the bubbling spots don't really look mouldy so I am not sure if this is the same or something different.

I then stripped off all the paint around the worst areas of bubbling and it is clear that the plaster is dampest in that area as it was significantly darker there than elsewhere. The darkest parts of the plaster were were the paint had bubbled the worst.

I assume that this is all down to condensation but it is hard to be certain. We are going to try to put up a curtain against the arch to the en-suite to keep as much of the moisture in there, but not sure how to tackle the damp plaster?

I'm tempted to leave it a few weeks to see it it dries out, then redecorate. I've seen some anti-mould and anti-condensation paints so these might be worth a try, but I don't really want to redecorate the whole bedroom if I don't have to as the rest is fine and we have a pot of the original paint left over to colour match. The ideal would be an effective anti-damp primer covered in our original paint, but not sure if this would be possible?

I'm not really much good at diy but money is tight so I want to tackle the problem myself if possible. Any advice or opinions on the problem and how to deal with it would be very welcome!!


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Joined: Mon Jan 28, 2008 10:10 am


Simply Build It

Postby lhreveretta » Tue Jan 29, 2008 1:51 am

I too had mould problems on my walls which is caused by condensation.
If your house is built roughly before the 1950's it will have solid brick walls and it won't be a cavity wall. What this means is the wall will be very cold compared to a modern cavity wall. Water moisture in the air will condense on the cold wall similar to water droplets forming on a window pain in winter. This will lead to the growth of mould.
The best (and most expensive) way to rectify this is to 'Dry line' the wall using timber baterns infilled with polystyrene and then covered with plasterboard,
Your room will be an inch or two smaler but it effectively 'insulates' the cold wall. The other alternative is to use polystyrene wallpaper, - not as effective and will dent when biffed, but is much cheaper.
Another alternative is to incease the ventillation in the room with an air brick or fan to allow the warm moisture laden air to escape before condensing on your walls.
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Postby briangibbard » Tue Jan 29, 2008 12:21 pm

Similar to dry lining solid walls I have come across plasterboard with polystyrene sheeting ( approx 2cm thick) attached to one side. This is then attached to the wall with adhesive. Has anyone experience of this and can comment on its effectiveness?
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Postby ahmurray » Wed Jan 30, 2008 5:59 pm


Thanks for the feedback. House was built in the sixties and definitely has cavity walls.

An unexpected development today we had heavy rain last night from the north (rather than the prevalent south west) and the bare patch of plaster which had been drying out was very damp this morning in three horizontal bands approx two thirds of the way up the wall.

The same north east facing wall on the ground floor is also damp to the touch, so it seems water ingress may be the culprit after all.

the house has modern UPVC cladding all around the roof and covering the whole of the first floor level which all seems to be intact so I can't see how water could be getting through that. Similarly roof seems in good nick with no tiles missing and the chiney is in the centre of the roof some way away.

I'm going to explore the loft tonight for any clues but failing that I guess I'll have to get a builder out to see if they can get up a ladder and find out what's going on!!
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Joined: Mon Jan 28, 2008 10:10 am

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