Fixing Penetrating damp in the Winter.

We moved into our new house over the summer. Its a detached two story property build in circa 1920. The exterior walls seem to be solid brick with a smooth white painted coating that looks to have been on for quite a few years. The whole house needs painting really, but thats not very practical at this time of year.

Over the last month or so we've noticed a lot of damp and mold inside the cupboards of the rear bedroom, the back of which is an exterior wall. There are two cupboards, either side of an inactive chimney breast.

We already know that the render on the chimney stack above the roof is falling off and needs to be urgently re-done. I'm not sure we can afford the couple of grand we've been quoted right now though, so I may just cross my fingers and wrap it in a tarp till next year until money is a bit less tight.

However, I'm not convinced that is what is causing the damp. The damp areas are the not adjacent to the chimney breast, in fact there is a clear area of dry wall between the damp and the chimney on both sides.

I found out recently that the gutters were completely blocked (full to the brim with soil and grass growing out!). I've now cleared that, but I'm not sure that was it either. The gutter is an old cast iron one fitted flush to the facia, so I think the water was mostly spilling over outwards, not down the wall. It's also severl feet higher than where the damp is.

While up the ladder doing the gutter, I saw that there appear to be areas of mold on the outside of the wall which match where the damp and mold is on the inside. The paint here is brittle and has lifted away from the wall in sheets. If it tap it, its obviously not attached to the wall anymore and will clearly flake away in big chunks given half a chance. The patches on the outside are narrower than on the inside, but look to be taller. The worst area is right on the corner of the house, and is about six foot high and a foot or so wide on the outside. The matching patch on the inside is the worst one and is a sort of triangle shape two or three feet wide at the bottom and about four feet high.

This wall, and that corner in particular, are quite exposed to the wind as our neighbours house is shorter and lower than ours, so I think the rain is driven fairly hard into this wall as we live in a very flat area.

I've also just noticed a similar situation with flakey moldy paint on the front corner of the house, and there is damp on the inside of that bedroom as well, with no chimney in the room.

I'm tempted to just scrape off all the brittle flakey paint and go over it with some exterior paint (Dulux weathershield or similar). But do I need to treat the wall first? If so what needs doing? Would the weathershield work as a stopgap solution till next summer when the work could be done in dry weather?

Also, how should I dry out the wall enough to paint or treat it in the winter weather when it never really gets warm enough for things to dry?

I need to get some sort of fix in place as I know its pointless trying to address the damp and mold on the inside until the source of the water is fixed. We're worried about the possible effect of black mold on us sleeping in the bedroom, not to mention my wife cant hang any of her clothes in the wardrobe!. I'm also worried about the further damage that freezing damp may cause to the exterior wall if left all winter.

Any advice or info appreciated. It's looking like the weather wont be too bad this weekend, so it could be a good opportunity to get up the ladder and sort something out which might not come around again for a while.

thanks in advance,

Ian

it sounds to me as though you have classic condensation issues due to cold bridging.

the most effective way to remedy this is to insulate the walls.

recently we used 25mm x 50mm tanalised battens, fixed to the internal walls, with 62.5mm kingspan kooltherm insulated dry lining boards, fixed to the battens.

this was done under b.c. reg's and was architect specified for 9" solid walls.

noseall said:

it sounds to me as though you have classic condensation issues due to cold bridging.

the most effective way to remedy this is to insulate the walls.

recently we used 25mm x 50mm tanalised battens, fixed to the internal walls, with 62.5mm kingspan kooltherm insulated dry lining boards, fixed to the battens.

this was done under b.c. reg's and was architect specified for 9" solid walls.

Click to expand...

Thanks for the reply.

What about the mold and surface damage on the outside? Is that damp from the inside penetrating out and under the exterior surface coating? In any event I presume I still need to make good the outside wall, can that just be painted over or will I need to treat and dry out the wall first?

Insulating the inside wall shouldn't be much of a problem. Do I need to do any special treatment and/or dry out the inside wall before putting on the insulation?

From your description, I would guess that you have rain blowing through the wall.
The rain has made the wall cold.
The cold has attracted the water vapour from the house to settle on the wall, where the wall being damp causes the moisture to move towards the outside of the wall, where it has frozen under the paint (the coldest point) and lifted it off.
The solution is to paint the outside of the wall with silicone paint, about three coats, this will stop the rain from coming through.
The damp patch will then gradually be absorbed into the rest of the wall and over perhaps a year will disappear.
Meanwhile, the wall being damp and cold, will still attract the damp in the air to condense on the inside and the patch will probably not disappear until spring or summer.
The solution is, to keep the wall warm.
Either by ensuring there is a steady passage of warm air passing it, or better still, trying to avoid any further condensation by keeping the temperature of the room steady.
A drop in temperature caused the water vapour in the air to condense on the nearest cold surface, probably your damp patches.
Check the windows in the morning, when its cold outside, are they misted up or running with condensation? If they are you need to steady the rooms temperature either up or down.
You also need to avoid creating water vapour by using the extractor fans in the kitchen and bathroom and keeping these doors closed.

Dampness on solid external walls is usually a compound problem of penetrating damp and condensation. (not rising damp as that doesn't exist!!)

The mould growth on the internal is 99% certain to be due to condensation. Mould prefers to grow on clean water - condensed water is perfect - and does not usually grow well on penetrating water due to the minerals and salts in the water. Mould growth would typically be found in corners and in wardrobes where there is less air movement.

That there is condensation and mould growth does not mean there is no penetrating dampness. The point has allready been made that penetrating dampness will reduce the temperature of the wall and this will in turn increase condensation.

Internal mould caused by condensation is black mould. This is nasty stuff and can cause health problems. My advice is clean and treat it with a treatment specifically developed for black mould. Try this link for more info. www.mgcltd.co.uk/

I suspect the mould you describe on the outside is some other fungi. It is unlikely to be black mould which requires stagnent air conditions.

The paint on the outside of your wall is probably causing more problems than it is solving. No damp treatment will keep dampness out - it will definitely get in. The paint on the outside is merely stopping the dampness from evaporating off. Most so called damp treatments do the same thing so are really a waste of time.

My advice is remove as much of the paint as possible and leave it exposed. Or, if you really must re-paint it, do so with a permeable product.

Second bit of advice is to follow noseall's advice to insulate the internal.

Third bit of advice is to fix the external leaks as soon as possible.

Thanks for the replies. we do get quite a lot of water on the inside of the windows in the mornings, so condensation is clearly happening. One of our kids had a bad case of croup recently and we were using a humidifyer at night to help him breathe, so that probably hasn't helped.

With regards painting, as the rest of the house is already painted its going to look pretty ugly if I leave patches bare. Are silicone paints permiable?

Yes they are, they are also virtually invisible.
They merely cause the rain to run off, instead of soaking into the wall.

A dehumidifier is a good idea, get one that collects about 10 litres per 24 hours, they never do collect that much, but they will collect around 2 litres per 24 hours, and if you can stop making excess water vapour they will certainly speed up the recovery.

One point, each of us produces about 2.5.litres of water vapour per day by breathing and sweating, this usually is removed from our homes by drafts and open doors and windows. (Children and animals tend to be more active so they produce more, old people less.)

If you have sealed your home to try to save on heating bills, then opening a window in the morning and evening will help to lower the humidity or better still use a dehumidifier.
Another point, dry air costs less to heat, so while a dehumidifier will use electricity you will use less heat and your home will feel a lot nicer.