Dry lining a damp wall

[Bodgit]

The problem (sorry it's a bit long):

Moved into our 150 year old house (soft brick and no DPC) a year and a half ago. I knew there were some damp issues and I've addressed some in other parts of the house, but we've just stripped the wallpaper off one room and the problems are a lot more severe than I thought.

The house is on a hill and this room is "underground" - there is no earth touching the walls as there are retaining walls outside with a gap between those and the house.

The room has always felt damp (black mould etc.) but I originally thought the problems were due to condensation. I've now pretty well ruled that out though. The whole house is well heated and there are few sources of water vapour.

The room has 2 external and 2 internal walls: - external wall 1: has no windows. Plaster has blown over full length up to a height of about 2 ft. No evidence of injected DPC but plaster has been replaced on lower half of wall previously. - external wall 2: contains 1 window. Wall in fairly good condition. Evidence outside of injected DPC. No evidence that plaster has been replaced. - internal wall 1: plaster blown over full length up to height of about 1ft. Plaster on lower half of wall has been replaced previously. Opposite side of wall has been drylined. - internal wall 2: has radiator. According to previous owner this has had DPC injected and plaster replaced about 5 years ago. Plaster coming away either side of radiator. Opposite side of wall is a fully tiled bathroom (rarely used). The only pipes in or on this wall are radiator pipes which are fully visible and not leaking.

The floor doesn't seem to be damp (carpeted). The skirting is made from quarry tiles. This area used to be the cellar of a large manor house. The ceiling (and floor of room above) is made from 14" thick reinforced concrete.

Where the plaster has blown the brick feels quite damp. The plaster that has not blown doesn't feel particularly damp. There are no pipes etc. except for the radiator. The rainwater goods are in good order. The floor level outside is about the same as the floor level inside, made from concrete and drains away from the house. I'm convinced this is rising damp.

The solution:

I know all the stuff about old properties - that you should allow the walls to breathe and and have lots of ventilation etc. but I can't really see that being practical!

This room has obviously been a problem for some time and has had many attempts to solve the damp issues.

I'm wondering whether the best course of action would be to dryline the whole thing. I would imagine I would need to use some sort of vapour barrier and treated batons. Does anyone have any idea how long this arrangement would last?

Any other ideas? I've seen membrane systems that you bury under the floor and run right up to the ceiling before plastering over, but as the floor is not damp I don't think this is necessary.

Any more suggestions would be very welcome!

[meow2222]

To understand why its damp and how to solve it, ask on

read the damp faq first.

NT

[Bodgit]

I've read the FAQ. I'm pretty sure I understand why it's damp.

Our house is a wing of an old manor house. In the 1850s this area of the house (17' square) was a coal cellar. The room next door (20' x

17') was a boiler room. The kitchen (20' x 17') was above. When it was built it probably didn't matter that it was damp - the coal-fired boilers, kitchen and open windows would have kept things pretty well under control. And if the coal cellar was a bit damp who cares? It was never designed to be lived in. But that's what we're trying to do.

I'm aware of your oppinion that rising damp doesn't exist. But in this case I think that's exactly what it is (yes - quite possibly brought about by the concrete floors that were laid in the seventies).

If I were to ask on PP, I'd be told to rip off all the plaster, re-plaster with lime plaster, take up the concrete floors and get some reed matting instead of carpets. I don't want to do this - I want a practical solution. I know that we've 'asked for it' by messing around with the natural breathability of the house. And I know that any solution would probably not last forever. I just want to make the room livable.

[meow2222]

Thats not my opinion.

I think youre jumping to conlcusions before theyre due there, you really dont know until you ask. The solutions I've seen on ppuk tend to be a good deal more practical than other approaches offered IME.

why not?

I think your assumptions may be getting in the way.

NT

[Andrew Gabriel]

Can you inspect it? Is the gap clear of any debris? Is is running with water?

That alone doesn't rule it out. For example, if those walls are remaining colder than the air temperature, they could be forming condensation. Have you checked the temperature of the walls where they are damp (need an Infra-red thermometer for this). Given the air temperature and humidity, it is possible to look up the dew point (temperature below which the wall will form condensation). See:

example, a room at 20C air temperature and 50% humidity will cause condensation on a wall at a temperature of 12C or lower.

Blown plaster is not necessarily a sign of damp. It could have been blown a week after being plastered, due to poor plastering.

[Stuart Noble]

In that case maybe all the walls should be injected. Better to do that yourself to ensure the right amount of fluid is used (I don't trust contractors). Damp on the lower part of an internal wall strongly suggests that it's rising, and this would be a low cost first step.

Wooden battens wouldn't last long on the wet side of the barrier. I suppose you could use plastic and stainless steel fixings, but I wouldn't embark on anything that drastic before trying other options. You'd be losing space and would have to line up the new surface with windows and doors somehow.

I know of one property round here where foil faced plasterboard was slapped directly on to damp brickwork during "renovation". The internal walls still look good 5-6 years later, so I guess they got away with it.

Let us know if you get anything useful from PP. As you say, restoring the place as a coal cellar isn't really an option here.

[Mark]

[Bodgit]

Yes - the retaining walls are about 4ft from the house walls so it's easy to walk around. The space between the two is filled with concrete which is about at the internal floor level and slopes away from the house into an open channel that runs along the bottom of the retaining wall. The only damp area outside is at the bottom of the retaining wall

- the channel gets a bit full of leaves sometimes and water can sit there, but it's not against the house.

Thanks for the info. I'll do that when I get home in a few days' time. I can accept that the external walls may suffer from condensation - the dadmage may well have been done before we moved in. But the internal walls must all be at around the same temperature, so I would have thought that if one wall suffered then they all would. I'll check with the IR thermometer and get back to you.

The wall feels wet though! I'm quite prepared to drill a hole in the wall to see whether the wetness is on the surface or penetrating right through. Anyone care to suggest a technique for doing this?

[Bodgit]

I'm prepared to give it a go. Can you suggest a good product? I've looked at Dryzone, which looks fairly easy - is it possible to hire the injection gun or should I just buy one?

Even if they were tanalised?

I don't mind losing a couple of inches or so as it's a fairly big room anyway. I can work around the door and window without too much fuss.

Would you agree that if it *IS* condensation then drylining would probably improve matters. If it's rising damp then the injected DPC would would offer the best bet, and drylining as well won't hurt.

[Bodgit]

Would a plastic membrane directly behind the plasterboard not be a solution?

We don't have a problem with the floor - just the walls. It might sound stupid but Is it possible to to just tank the walls?

[Stuart Noble]

Dryzone only needs a mastic type applicator but I have my doubts about it. The idea that the moisture in the wall magically disperses the cream in all directions sounds a bit like wishful thinking to me, but at least it wouldn't cost much to try. I'd rather rely on the traditional pump method. Hire it for a weekend and take your time. As it says on the Dryzone site, the disadvantages are that it takes longer to apply and longer to dry out, neither of which should be a problem with d-i-y

Even then

I'm just wary of drastic measures that seem like they should work logically. I'd rather confirm the cause before discussing the remedies. See below

There are simple tests for condensation. E.g. fix a mirror to the wall and see if it mists up a) with the room heated normally and b) overnight with the heating off. I had a similar situation in one of our rooms a few years back that had a framed mirror sitting tight against an outside wall. The hardboard backing was always dotted with mildew but never any sign of moisture on the glass. Probably not a foolproof test, but pretty close. The other thing I'd do is contact a few local builders. Pick their brains