Just had the exterior of a Victorian house repainted/re-rendered. The solid
are about 450mm thick. There was penetrating damp on some of the inside
These walls are still damp but we assume that it will take some time for 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
The building is about 15m high. Damp occurs at all levels. How long is
to wait before we can expect the inside to be dry, assuming the source of
has now been eliminated? The building is well ventilated and it is not
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.
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
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
All these make substantial differences.
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.
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
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.
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
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.
On 11 Sep 2005 08:06:20 -0700, firstname.lastname@example.org 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?
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.
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%(:-
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.
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.
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
As I said previously, we've had little rain for a long time but, when
it happens, the wall gets no wetter.
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