Condensation/mould problem: what paint etc?

[Lobster]

I have a ceiling area which is very prone to condensation and mould problems - in this picture it's the funny-looking arrowed area (characterful, as the estate agents would put it) which protrudes downwards into the room, and is very cold due to the close proximity of the valley gutter above it.

There's not really any way of getting any more insulation above the ceiling, and unless I start cladding the ceiling with polystyrene sheeting (which I really don't want to do), so I'm trying to prevent the recurrence of mould.

This is in a rented-out house, and it's not easy (ie impossible!) to educate the tenants about ventilating the place properly. I'm between tenants right now, and have just cleaned away all the black gunk using proprietary bleach-based mildew remover which worked a treat.

Fiinally, the question!

I want to repaint the ceiling now, but what best to use? Do these bathroom/kitchen paints contain fungicide to prevent regrowth? Browsing at B&Q just now, it didn't seem so. I came away with some "fungicidal wash" which you can use pre-painting - will that do the trick (insofar as anything will?) if I apply it prior to ordinary emulsion? I've heard about anti-condensation paint but couldn't find any at B&Q - or is that just the kitchen/bathroom stuff?

Any advice appreciated...

David

[Andrew Gabriel]

Does that imply there is some? What is it? Even just an inch thick sheet of cellotex would stop this.

If there is no gap, you can get cellotex-backed plasterboard, and replacing that part of the ceiling with it would work well (or a 1" sheet of ordinary cellotex behind standard plasterboard).

Nothing you paint on it will stop condensation when it's cold and below the dew point.

[Stuart Noble]

AFAIK anti condensation paints contain microspheres. Maybe if the coat was an inch thick it might help

[meow2222]

if you had to put an inch of insulation on the surface, a stepped patch will probably look as good as mould, or better.

Usually a waste of time explaining things, most tenants couldnt give a toss. As far as theyre concerned its your problem and doesnt concern them.

The other approach os to reduce the interior RH. This might take nothing more than a sheet of paper suggesting ways to save money, including turning the ring right down and using a lid. And how to make your room fresh by airing it in the am etc. Can sometimes work.

NT

[Lobster]

In response to Andrew - the trouble is that not only is there this valley above, but the roof has a very shallow pitch. When I originally refurbished the place 2-3 years ago I put about 9" of Rockwool into the roof space, but that area was a nightmare: I ended up lying down full length and poking the stuff in using a stick, also trying to maintain adequate ventilation up there. I think the only way of sorting it properly would be to remove and rebuild the valley gutter or to pull the ceiling down and start again, neither of which appeals!

antibiotic like penicillin work better though (thinking of Alexander Fleming and his bread mould)? Having said that, the mould is definitely only the surface as I've been able to clean it away completely (it's also on glass and uPVC window frames) - wouldn't a drug in the paint only act if the mould was *within* the interstices of the paint?

+

Well yes, as I said below. Typically they tell you there's 'damp' - ie meaning leaking from outside - and it's hard to convince them that the reason I'm not employing armies of roofers etc is not because I'm a tightwad, it's because I know full well there's no leak to cure!

Mm. I tried replacing the bathroom extractor fan with a humidistat-controlled model, and suggested they routinely left the upstairs doors open during the day to let it do its stuff, but I suspect they didn't. Bathroom is fine and dry though, with no reccurrence of the mouldy silicone I replaced at the time!

I wondered about providing a dehumidifier, but rejected that on the grounds that they'd be unlikely to use it anyway due to the running costs.

David

[meow2222]

If youre getting condensation despite 9" of insulation, RH is the problem rather than inadequate insulation.

Penicillin, like any antibiotic, will only kill some bacteria. It doesnt affect mould at all.

... more evidence you've got an RH problem

The salicylic acid formed is water soluble to some extent. The paint is not a perfect vapour barrier. Hence salicylic ends up on the surface as well as within the paint. I tried it and it worked well.

yes, I think educating tenants how to solve what they see as your problem is going nowhere. Theres always a reason theyre tenants.

If the door isnt airtight it'll work even with it shut, although leaving the door shut is a daft way to run a bathroom really. If you add a weight/pulley or spring system and suitable catch type, the door would stay open when room unused.

So don't give them the choice. Wire it in. Its perfectly reasonable to provide fixed equipment to counter their mismanagement, since its necessary for health.

Tenants can counter any active system if they choose, but usually they dont bother.

The other approach is to have in writing their obligation to air the bedroom in the morning, leave the bathroom door open etc, and if mould occurs due to failure to do this you can writtenly remind them that they would be responsible for damage caused by their breach of contract, reminding them politely to do their required bit.

Explaining they have a choice between living with mould and no mould, depending on their actions, sometimes works.

NT

[Lobster]

No the 9" is over the main roof area; specifically under the inaccessible valley gutter bit there will be bugger all.

Right, I was getting muddled - Flemimg found that mould *produced* penicillin, which killed bacteria, didn't he.

Before I nip down to Sainsbury's, is there evidence other than your experience that aspirin kills mould, though?

That idea's a distict possibility!

How could that be done in a way which they'd be unable to simply bypass, though? (ie using the off switch) once they realise what the running costs are!

I think I will, before the next ones move in.

David

[Peter Johnson]

Would a vent in the door help?

[meow2222]

Oh i see. Well, you need insulation. Why not make a feature of surface applied insulation. 2 sheets of half inch, one smaller than the other, like a shallow pedestal upside down, and a light fitting in the middle or something. Or remove the PB and fit whatever insulation you can. Dunno. But somehow you need to deal with it, as paint wont stop the damp and that'll ruin things anyway.

Aspirin reacts with water to produce salicylic acid, thats the active ingredient. Google away. Add a pinch of copper suphate from the chemist as well and you've got more mould kill power. Go easy on the cu though, its not white.

no off switch, no plug. Not 'ard. Also the run costs are quite low for a dehumid, you're talking about 200w only on for a fraction of the time, and on in winter only.

NT