How long will damp take to dry out?

Just had the exterior of a Victorian house repainted/re-rendered. The solid walls are about 450mm thick. There was penetrating damp on some of the inside wall. These walls are still damp but we assume that it will take some time for the the brickwork to dry out. (In fact some of the internal damp seems to have got worse - probably because it is now less easy for trapped damp it to escape externally).
The building is about 15m high. Damp occurs at all levels. How long is reasonable to wait before we can expect the inside to be dry, assuming the source of damp has now been eliminated? The building is well ventilated and it is not condensation.
regards, Andrew
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"Andrew" <-> says...

Unless you rendered with lime mortar and painted with a porous paint it quite possibly won't go away at all.
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If you have eliminated the source it can take along time to dry out e.g. year or more. Also old lime plaster if damp for a long period can become hygroscopic i.e. absorb atmospheric moisture. This results in intermittent damp patches in peculiar places e.g. half way up walls, and is most noticeable in humid weather like today or when there is a change from cool to warm/humid. So give it a year or so.
cheers
Jacob
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snipped-for-privacy@jpbutler.demon.co.uk wrote:

I would not be so pessimistic.
IF you have no rising damp - and its a big if - 4-6weeks will take care of damp plaster.
If you have sodden internal brick walls, expect issues all winter but central heating does dry interior walls pretty effectively with cold dry air outside.
If you haven't fixed the rising damp, then as another poster has bluntly put it, with a waterproof covering in the outside, you will get perpetual damp inside.
Its not clear exactly what is damp, whether damp proof or breathable membranes are, or what construction the house is, and its insulation standard.
All these make substantial differences.
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Rob Morley wrote:

I'm sure the OP will be pleased to hear that! Unless he runs a laundry and has no heating, I'm sure the damp will dry out just fine since it will presumably no longer be pouring through from outside.
Where do you find these plasterers that are prepared to bugger about covering whole walls with wet sacks? Do they smoke clay pipes? And what the hell use is porous paint? All water based paint is porous, as you soon discover if you use it to cure penetrating damp. Pliolite resins are a *major* improvement in masonry paint but even they are far from being impermeable.
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solid
Mention damp and period buildings on the internet and you can guarantee an instant if-it's-not-lime-your-doomed response. Apart from for really old buildings, I've never come across builders in the real world even mention the stuff.
As my house has had a concrete render for least 100 years, replacing it all with lime seems overkill and probably unnecessary, even if it was an option. If the damp doesn't dry out, I'll just paint over it and manage the problem. However, from the responses received I guess I should wait a few months to see if the problem is cured.
regards, Andrew
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"Andrew" <-> says...

I was surprised I was the only one - someone has to do it, it's traditional :-)
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Andrew wrote:

You never told us what you did to solve the damp problem. If rerendering was it, it may or may not dry out, its not really a good solution to damp.
NT
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snipped-for-privacy@meeow.co.uk wrote:

It's often the only solution short of re-building the house. If water is prevented from entering the wall from the outside, why wouldn't the inside dry out?
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stuart snipped-for-privacy@ntlworld.com says...

Because moisture also comes from inside and below?
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Rob Morley wrote:

Lime lovers seem to have the idea that human activity generates buckets of water that are prevented from evaporating by cement and/or a coat of Dulux on the outside of the house. With normal heating and ventilation this source of moisture shouldn't be an issue. If water is entering from below then you need to stop it rather than accommodating damp as a way of life. It really isn't very healthy
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On 10 Sep 2005 12:24:47 -0700, snipped-for-privacy@evemail.net wrote:

Are you sure you don't have another source of damp?
DG
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Yes. The water was trapped between internal (which had been plastered over) and external rendering and it was simply hydrostatic pressure that eventually forced it into the house. In any case, unlesss every cat for 50 miles is climbing on my roof, nightly, to urinate on the rendering (I think I'd have noticed (:- ) rain is the only possible source - and we've had very little of that in this area in the last 2 or 3 years. But if you have a credible alternative, I'm listening. The novelty of bare plaster in the living room is beginning to pall.
Tony.
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On 11 Sep 2005 08:06:20 -0700, snipped-for-privacy@evemail.net wrote:

A 75 cm thick wall full of water ? :((

How much does the dehumidifier collect in it's 8 hour session?
Noticing that my vacuum foodsealer sucks moisture vigorously out of stuff such as onions I wonder if sealing the area with a visqueen membrane using flexible RTV and vacuum pumping it out with an aspirator (killing 2 birds with one stone) might work?
http://en.wikipedia.org/wiki/Aspirator
http://hyperphysics.phy-astr.gsu.edu/hbase/fluids/aspir.html
Be Careful ! see pics...
Possible snag, onions are of course compressible walls are not. But if the wall is permeable enough it might be worth a try.
I want a Nobel prize if it works.
DG
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About 3 pints. The arithmetic is, to me at least, interesting.
The wall has a total volume of about 1,814, 400 cu in, and the split in the flue was near the top, so the whole wall was soaked. If 10% were water and it dried in 6 years (2190 days) it would mean that 181440/2190 cu in would have to be released, on average, daily i.e. 2.4pts which, taking into account atmospheric moisture ( the windows are open for the other 14-16 hours) and the fact that the dehumidifier and heating have accelerated the process recently, is not too far from what I was getting.
A curious feature, which supports my contention that the water is trapped between the 2 coats of render, is that turning off the dehumidifier, during the last week or so, causes the internal wall to become drier, leaving gravity, and the air, working on the newly exposed lower part of the outside, to take over the drying. When the dehumidifier is on, the resultant dry atmosphere, internally, causes moisture to be drawn into the house.
Of course, this is all ifs buts and maybes, but I'm fairly confident that my reasoning is sound, even if the estimates are no more than guesses, and a little less confident that the end is in sight. Please God, don't make it more than 10%(:-
Tony/
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snipped-for-privacy@evemail.net wrote:

I'm far from convinced. Few walls are so watertight, not one single crack anywhere, impermeable bottom, than free water can not escape. If yours were filled with free water, and sealed like a Roman pool (not easy even when trying) one small drill hole would empty it.
I expect you have an ongoing source of damp. I would check the property over for all the usual causes of damp.
NT
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See paragraph 2 of my post on September 10th. That's where I started, and have checked since.
Tony.
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snipped-for-privacy@evemail.net wrote:

I can't see that it's possible to "trap" water between 2 coats of something permeable. But if water pours in at a specific point when it rains and then has to dry out gradually by evaporation, the wall may well give the impression of being permanently soaked.
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I was using the word 'trap' loosely. The wall is enclosed by 4:1 cement render. In this part of the world just about everything is a 4:1 mix. I didn't put it there, nor would I have, but I've learned from experience that the locals have their own way of doing things, based on their experience.
As I said previously, we've had little rain for a long time but, when it happens, the wall gets no wetter.
Tony.
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replying to Rob Morley, Master maz wrote: Yeah if it’s built with soft stone. No need for lime mortar and porous paint everytime
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