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Old 04-09-2010, 12:07 PM   #1
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Damp internal walls


Hi I live in an old house in the country subject to very damp weather. The walls are solid and, in some areas, suffer from dampness. At some stage in the future I will dry-line the walls to solve this problem but, at the moment I have to paint them. The walls are plastered and, a short while after painting, damp patches start to show through the paint with mould showing through. Is there any way I can pre-treat the walls to prevent this growth of mould and improve the life of the paint as, in some cases, the walls have to be painted twice a year to improve appearances. I had thought of treating them with 'Dulux Weathershield Multi-surface Fungicidal Wash' prior to re-painting again. Does anyone have any better ideas?

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Old 04-09-2010, 04:23 PM   #2
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Damp internal walls


What are the walls made of?

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Old 04-09-2010, 05:24 PM   #3
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Damp internal walls


and where are you located???
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Old 04-10-2010, 10:47 AM   #4
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Damp internal walls


Hi Chrisn & Slickshift I live in Ireland where the climate is very wet and cold, particularly in the Winter [ and often in the Summer]. As I said above I live in a very old house. The walls are made of stone and are rendered; there is no damp course.
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Old 04-11-2010, 07:18 AM   #5
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Damp internal walls


You live under extreme conditions but nonetheless some common ideas apply; if you have moulds on interior surfaces, then you have provided (a) food for the mould (b) suitable temperatures for it and (c) enough humidity in the air - or on the wall - for it.

'Temperature' is not something you can do much about, nor is food, as mould can grow on anything - even each other. But moisture level at the wall is something we can control, either by removing the source of the water, removing its access to the wall, or by lowering the relative humidty at the wall. The first thing is to remove the water from access to the wall and that will depend on whether the wall is above or beneath ground level.

Once you've done all that can be done to limit the access of bulk water to the wall, then attack the vapour. Use fans, dehumifiers or heaters to reduce the relative humidty against the wall by evaporating the water that is there that you can't see.

A lot of people think that applying this-or-that "paint" to the inside surface is enough; sometimes it is but most times it isn't. All they're doing is forcing bulk water to go elsewhere or providing more food for the mould. A cheap alternative is to increase ventilation and air movement in that room by using fans. A good treatment to kill off the residual moulds might be appropriate too.

I am one of several thousands of Canadians who is one-quarter Irish, on my fathers' side. A lot of English- and French-speaking Canadians - as well as Americans - have some fraction of Irish in them but due to the circumstances around the turn of the century, I don't know exactly what part of Ireland I can trace back to.
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Old 04-11-2010, 02:47 PM   #6
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Damp internal walls


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You live under extreme conditions but nonetheless some common ideas apply; if you have moulds on interior surfaces, then you have provided (a) food for the mould (b) suitable temperatures for it and (c) enough humidity in the air - or on the wall - for it.

'Temperature' is not something you can do much about, nor is food, as mould can grow on anything - even each other. But moisture level at the wall is something we can control, either by removing the source of the water, removing its access to the wall, or by lowering the relative humidty at the wall. The first thing is to remove the water from access to the wall and that will depend on whether the wall is above or beneath ground level.

Once you've done all that can be done to limit the access of bulk water to the wall, then attack the vapour. Use fans, dehumifiers or heaters to reduce the relative humidty against the wall by evaporating the water that is there that you can't see.

A lot of people think that applying this-or-that "paint" to the inside surface is enough; sometimes it is but most times it isn't. All they're doing is forcing bulk water to go elsewhere or providing more food for the mould. A cheap alternative is to increase ventilation and air movement in that room by using fans. A good treatment to kill off the residual moulds might be appropriate too.

I am one of several thousands of Canadians who is one-quarter Irish, on my fathers' side. A lot of English- and French-speaking Canadians - as well as Americans - have some fraction of Irish in them but due to the circumstances around the turn of the century, I don't know exactly what part of Ireland I can trace back to.
Hi CCarlisle Thanks for your comments which are food for thought. I actually have dehumidifiers going 24/7 in these rooms. I have reduced the ground level on the outside of the wall and I keep the gutterings clean. All this helps but There is still the problem with dampness. The walls are about 600mm thick of rendered stone. I do intend, as stated earlier to dry-line the walls at a later date but for now can you recommend a treatment to kill off the moulds? As to your last point many good people left Ireland over the years and settled in America and Canada
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Old 04-11-2010, 03:13 PM   #7
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Damp internal walls


Well, the quick, cheap and easy solution to 'moulds' is usually a dilution of chlorine bleach; now there's a lot more to it than that, but that will do a lot for your problem.

Now I can't recommend more than that because I don't know what bleach products you have available to you but I'm looking for a laundry bleach product that is known chemically as a 4% solution of sodium hypochlorite. That cost about $1 a liter here. If you have that, dilute that 1:10 with water and spray that directly on the walls.

It will only be marginally effective but it will kill off the mould living on the surface of the wall; does nothing for the roots that are deep into the plaster or the grout, so with time the moulds will come back again.

With the dehumidifiers, you are encouraging moisture to come into your home by creating a relatively 'dry' room. The moisture in the walls will naturally migrate towards the dryness and keep doing so until it reaches equilibrium - which it never will. They are a good temporary solution to drying out buildings after a flood - but used on a continuous basis does nothing but make your electricity bill higher.

Where are you locate exactly in Ireland, may I ask?
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Old 04-12-2010, 08:06 AM   #8
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Originally Posted by ccarlisle View Post
Well, the quick, cheap and easy solution to 'moulds' is usually a dilution of chlorine bleach; now there's a lot more to it than that, but that will do a lot for your problem.

Now I can't recommend more than that because I don't know what bleach products you have available to you but I'm looking for a laundry bleach product that is known chemically as a 4% solution of sodium hypochlorite. That cost about $1 a liter here. If you have that, dilute that 1:10 with water and spray that directly on the walls.

It will only be marginally effective but it will kill off the mould living on the surface of the wall; does nothing for the roots that are deep into the plaster or the grout, so with time the moulds will come back again.

With the dehumidifiers, you are encouraging moisture to come into your home by creating a relatively 'dry' room. The moisture in the walls will naturally migrate towards the dryness and keep doing so until it reaches equilibrium - which it never will. They are a good temporary solution to drying out buildings after a flood - but used on a continuous basis does nothing but make your electricity bill higher.

Where are you locate exactly in Ireland, may I ask?
Hi CCarlisle Your point is well made and hence my intention to install a system of dry-lining to the walls eventually but dehumidifiers do keep the rooms relatively dry. I live in Galway which is on the West coast; near The Atlantic.
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Old 04-12-2010, 08:35 AM   #9
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Damp internal walls


Hi again!

Not sure what you mean by a 'dry-lining' system...can you explain?

Yes, the dehumidifiers do the trick but I jsut wanted to make the point that it is on a temporary basis only and certainly not a long-term solution. But permanent solutions require some investment in any case....

There is a product that I have heard mentioned on these boards and that is "Dry-Loc" by UGL. It is a paint that is reported to withstand a certain amount of water pressure behind a masonary wall; I really don't know if that type of product would be suitable for your circumstances nor if they are even available in your country but I think this is what you were hoping to find. At least their website will give you the pros and cons of using it and from there you can perhaps find a locally-made product.

But either way, the moisture has to be coming form somewhere amongst the walls, the floor and the ceiling. Is this a basement-type room, partially underground or are you talking about walls of room that are exposed to the elements?
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Old 04-12-2010, 08:42 AM   #10
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Damp internal walls


Plus, you might want to make sure you are using the right type of paint -perhaps supplemented with an added extra fungicide - for painting over plaster or cement which, has an alkaline pH. Not all paints will be suitable for this but some are made for that.

The fungicide will sit on the dried paint surface and repel mould from the top down. If it has extra fungicide in it, even the base will offer some protection. You should be able to get all that at paint stores.

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