As other posters are saying, this just doesn't sound like rising damp.
However if you do decide to chase the rising damp idea, avoid wet injection pressurised damp proof injection systems. These work by injecting a water diluted silicone (or similar chemical) into the wall & then you have to wait for the old water PLUS the new water to dry out before you (might) have a dry wall.
A better alternative is Dryzone Cream made by Safeguard Chemicals of Horsham. It changes the chemical nature of the mortar bewteen the bricks rendering it waterproof & there is no new water going into the wall. You still have to drill 12mm holes into the wall every 100mm, as in the wet systems, but you drill into the mortar which is easier. Then you squeeze the cream into the holes by a special applicator gun
Also how old is the house ? Should there be a membrane at all ? In very old houses in a damp location you need the whole floor area to evaporate the moisture. It may be this membrane is pushing all the damp into the walls until they are saturated amd things start to fail.
Unless it's underground and you've no other way of removing the water I wouldn't.
If the outside is already rendered and painted, I'd try a pliolite based solvent masonry paint. Johnstones do a a product called Stormguard, and most trade paint companies have equivalent brands. These are *vastly* superior to normal masonry paints and aren't that expensive. That should at least eliminate penetrating damp as the cause. Stone sills are also a major source of damp, however sound they look. Water often sits in puddles, and has time to soak into the brickwork and travel through the mortar. In a brick built house rising damp is probably the least likely source.
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This is classic stuff, the damp old Victorian house that goes from bad to worse despite all the efforts of dampproofing 'specialists'. And the cause? The fact that all the wrong things are being done. This scenario plays out over and over again, so often its a well known deal.
Add to this the twin facts that a) you dont understand how damp is managed in Vic properties, and b) you've made mistakes in your conlcusions, and you cant get to the bottom of it either.
First, if you want to understand damp and Vic properties, I'd recommend a good long chat at
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whats going on:
Vic houses handled damp fine when they wre built, they were not pits of damp. So the basic design is good.
Since its damp now, it is what has been changed that has caused it.
What has changed?
Airtight double glazing stops ventilation
Chimney blocked off
Maybe draught proofing elsewhere too
Gysum plaster and emulsion
Cement render and paint
shower installed
All of these increase the damp levels in the walls, and some properties then begin to fail to deal satisfactorily with the damp.
Contrary to your conclusions, the cause is indeed condensation. Why did the dehumidifier not cure it? Primarily because it has been going on for so long that the walls have become soaked, so that it will take many months to dry them out. Also there are other works that will need doing to fix it properly, eg the exterior render will be an ongoing problem.
What else needs doing?
The first thing to understand is you need to allow the wall to dry out, not trap all that water in it, which is what all your presently considered works are about. No to tanking No to rendering No to painting with water resistant paints No to a 3rd DPC (!!) (slate should last much longer than 130 years)
Yes to: Humidistatic dehumidifier Lowering ground levels if theyre at or above the dpc Checking the drain channel drains properly Repoint all failed mortar with lime - but dont remove anything thats stuck hard. Removing all exterior render, and finishing by either cleaning the bricks up, or if theyre too much of a mess, lime render. Remove interior plaster and replaster with lime, painting with lime based paints, not emulsion. Checking ground water drains away from the house, not to the walls. And I would add ventilation to the house for your own health, though this is not necessary re damp until such time as you stop using the dehumidifier.
Pay attention to major sources of damp within the house: Install dehumidifier in bathroom, or maybe a fan. And possibly enclose the shower so it doesnt produce as much steam in the room, if practical. And preferably install a cooker hood
Understand some basic concepts with these houses:
More damp is produced inside by breathing, cooking and showering than comes from outside
Thus what is wanted is porosity, to allow the damp out, quite the opposite of sealing.
Damp proofing companies do work so they can get your money.
If dealt with appropriately, a Vic house with no dpc, no render, no waterprofing treatments etc can be dry and healthy.
Also be aware that a 9" wall will take a very long time to dry out, even with the above treatments done.
BTW there is one gotcha: the bricks will be very soft, and the cement render hard, and it is _very_ easy to do serious brick damage when removing the render. Proceeed only with serious care on this point.
I'd agree with that. It's the conclusion I came to, despite all the advice I was given by "experts" when I was considering buying a damp Victorian house a couple of years ago.
There are some additions. Make sure the tumble drier is properly vented and the filter is clear. Don't dry washing in the house. Open the windows wide and let the wind blow through the house once a week in addition to normal good ventilation.
I also think similar things apply to much more recent buildings. I've experienced these problems in '60s flats and a '50s bungalow. Efforts to keep rain and weather out cause troublesome build up of condensation. Once the condensation has built up in the structure it has every appearance of coming in from outside. It takes months to dry out.
Don't paint outside walls unless it is absolutely necessary, and then use a paint that won't prevent the wall to dry outwards.
(I'm trying to dry out the insulation in an old freezer at the moment - and it is taking weeks. Think how much longer a wall will take.)
And don't forget there's little money to be made from giving "ventilate - don't cause moisture buildup" kind of advice.
The oracle has spoken! Your condensation theory is blown away when you consider that most of these houses get the same symptoms after a heavy shower in mid summer, when there are insufficient cold surfaces to cause condensation, and the windows are wide open. The idea that a house should allow the passage of any amount of water through the walls and wait for it to dry out is Dickensian, and faintly ridiculous in this day and age. It means houses would effectively be damp for at least 9 months of the year. What has changed to make Victorian properties leak like a sieve, when presumably they didn't originally, is IMO the degradation of the lime mortar. If that powder between the bricks in a 9" wall is all that's protecting you from the elements, then you need look no further. Replacing it with mud would be an improvement.
I have not observed that to be the case, although of course it will be in some properties
A summer shower sends the RH up to 100% rapidly, inevitably increasing the odds of condensation.
There are many buildings with penetrating damp problems, which will fit your above analysis. Many of course have both penetrating damp and condensation problems.
see below about how this can cocur
that may be why 'any amount' wasnt suggested
Another classic misconception there. As air exchanges between a warm house and cold exterior, 2 things occur.
Cold damp air comes into the house and is warmed. Since warm air can carry much more moisture than cold, its RH drops considerably as it is warmed.
Warm air that feels dry is carried outside. Warm air can hold lots more moisture, and as it cools outside it becomes damp air.
The heat differential plus ventilation results in drying of the interior, even during wet winter months. It is only on wet summer days that ventilation does not produce this drying effect, since incoming and outgoing air are at apx the same temp. And in any place where its cooler inside than out at the time, which is not unusual, with RH at
100% outdoors, condensation is liable to happen.
originally they had:
open chimneys, which accept the 56" of rain per year we get draughty sash windows draughty doors no wall dpc in most cases no floor dpc in most cases porous bricks and lime mortar and unsarked slate roofs, which allow some rain in too.
Mud soaks up water, so that wouldnt help. Mud also has a much lower compressive strength in newtons per square metre, so would make the walls unstable. Wet mud has very poor compressive strength, rather than being an improvement it would be dangerous.
Mortar in poor condition can as you say cause penetrating damp, and this is a problem on some old properties. The solution is to repoint in lime, because lime helps the wall dry out after the rain. Vic house walls are not normally waterproof, rain soaks in, they rely rather on the rain then evaporating away again quickly enough afterwards to avoid rain penetration.
Let's just say I've never noticed condensation in summer. Not in the bathroom, or on the windows, or anywhere else I expect it in winter.
So your beloved lime is self regulating is it? When we get driving rain for days on end, it stops absorbing water at a certain point does it?
I'm sure lime is fine in the right sort of thick walled country residence but not as a general repair mortar for 9" brickwork in terraced houses. Use a pozzolan? Well then you might as well use cement.
kind of hard to go past saturation I'd say. But maybe you know a way. The water doesnt flow from outside to inside quickly, so the inner wall face doesnt get wet because of it. Victorians sometimes used cavity wall construction to reduce penetrating damp in cases where heavy driving rain was expected. They were not introduced for insulation.
repoint in
residence
houses.
Its already clear you dont know much about the subject.
The vast majority of Victorian terraces wre built with lime mortar, its success is well and truly beyond doubt.
As the extensive use of render and pebbledash will testify. Do you think they put that stuff on for aesthetic reasons? No, hold on, I've got it. It's because they're all stupid, right?
It is a waste of time if you don't put forward a valid argument. Lime mortar in the sort of quantities you would use for re-pointing will not stay put and will not resist heavy rain without some kind of setting. A pozzolan will provide this but even the staunchest, Morris dancing, lime lover will admit that it negates the benefits of lime. Perhaps you can enlighten us as to how these problems are overcome in the real world.
Some (but by no means all) victorian houses did use a little cement in the lime pointing (which is just the outer 1/4").
Yes -- they didn't like the look of commons. Depending on the area, some part of the house (often the front, but it varies from nothing through to all the external walls) would use something more expensive. Mine is not untypical -- there are no commons visible from the front. The ground floor uses (what were) expensive facing bricks, but these are very soft and are somewhat protected from the weather by a canopy roof which runs the length of the terrace, forming extended porches and ground floor bay window roofs. There is a 12" render skirt to protect the soft bricks from ground splash. The first floor front is a mixture of pebbledash with rendered highlights around windows, corners, etc. (Pebbledash at ground level was not considered good because of what happens when you walk into it.) The side and rear external walls are all commons, no render/pebbledash/skirts.
Neither will cement mortar. Like cement based mortar, you keep it covered until it sets if there's a danger of rain. It just takes longer.
30 years experience of what? Eg 30 years as an architect or a brickie doesn't make you a structural engineer.
Yes they are (or were) really stupid in a lot of cases, it was done because pebbledash was considered the 'in thing' by some people at the time. and they wanted their vic terrace to look 'modern' and different to the others in their street..
Adding a vapour barrier to a wall or reducing it's vapour permeability without understanding where humdity is coming from or going to, can introduce or compound damp problems instead of solve them in a lot of cases.
"> Yes they are (or were) really stupid in a lot of cases, it was done
There's usually a practical basis for fashions in building, and it's difficult to think of anything that is so hard wearing and waterproof. Had they known about pva when most of it was done, it probably wouldn't have cracked the way it has.
Pebbledash is hardly a vapour barrier. The idea is to resist water droplets. Vapour is air, and nothing short of a sheet of plastic will stop, or significantly reduce, that.
Well, for lime and natural cement, at least a couple of thousand years. Portland cement was new in Victorian times, and too expensive to use as a general purpose building cement in houses until sometime around 1920.
It does, but it doesnt guarantee much. It takes time, opportunity, a fair brain and interest to learn. If you cant work out that the Vics used lime mortar with great success on 9" terraced house walls, I guess you must be missing one of the things in that list.
Of course if you have some wonderful insight none of us have, and can in fact explain why and how millions of Vic houses have actually not stood the test of time with lime mortar, despite all appearances, please feel free to educate us.
I think IMM already agrees with you.
sounds none too logical
In a lot of cases, yes. There are plenty of walls built out of basically mixed junk, and look a right sight when the render is removed.
Also it was put onto 4" walls to waterproof and help stabilise them, 4" house walls are not particularly good.
Also of course it was put on for the wrong reasons, just as it continues to be widely today. Regrettably, a lot of work is done simply so that the builder can receive payment for it.
The Victorians were 1 sd lower in iq than we are today, and that is significant, but otoh there were far fewer subjects for people to go into, and building attracted much greater levels of talent than it does today. Looking at those old buildings suggests plenty of skill in their construction. So if anything, Vic builders were probably just as smart as today, and maybe more so.
Feel free. So far youre given no substance on that point at all. But maybe best to just concentrate on your claims so far.
Well, plenty of people are doing it, and find plastic sheet or sacking makes it work just fine.
does it
You would need to start by telling us what you claim these problems are! I've addressed the first one - the rest you dont even mention.
different
waterproof.
Well, plain brick seems to have done just fine... so it doesnt look like that was the reason.
If you think adding pva stops render cracking on Vic houses, this shows just how little understanding of the subject you have.
different
exactly. What is the practical basis for stone cladding Stuart?
The practical basis for it is simple: its a means for builders to take money off customers. Just like render, and a host of other worthless jobs we see regularly on houses.
Hmm. What kind of response is that? Is quoting web sites the best you can do?
Well I've owned 2 houses that suffered damp and maintained at least 3 others, so I've been able to monitor things pretty closely over the years. How about you? Out of interest, check out the qualities of styrene butadene copolymers in render mixes.
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