Damp problems again!!!

Hi All,
More damp questions - apologies for boring anyone.
The background - my living room has damp problems mainly on two walls - it rises up to within a foot of the coving. 1870s house solid walls. I've done all the usual checks. It's not condensation and there is evidence it's been a problem before. Ground level is below both the slate dpc and the silicon DPC. Room 25ft by 10ft.
Recently had a quote by a damp company (~3K) to do the following;
- Inject DPC (already has a silicon one and a slate one) - Strip plaster on two walls (total 35ft inc 3 windows and frenchdoors) - Treat the two walls with some sort of waterproofing "stuff" - Replaster two walls - Remove bottom 6" of external render and rerender with bellcast. - Repoint two courses of bricks (35ft) below the DPC.
My plan is to get them to do the DPC (and wall treatment???) and I'll do the rest. I appreciate the injected DPCs are not trusted by many but I want to give this work every chance of fixing the problem.
For the internal walls; - Should I plaster or use plasterboard with a skim? Damp Company didn't like the idea of plasterboarding as it causes problem with the wall treatment. - If I plaster, what type(s) of plaster should I use? I would get someone in to do this. - If I plasterboard it presumably celotex could be used to aid insulation? - Could I "dot 'n dab" plasterboard direct to the wall? - Should I treat the bare brick in any way prior to this? - Do I need to give the walls time to dry out? - If so roughly how long?
For the external walls; -What mix of render? -Any tips with the bellcast beading? How far above the DPCs should it be? -What mix for repointing below the DPC? -What mix for repointing above the DPC?
Incidentally, I am getting a few more quotes!!
All experiences/advice welcome...
Cheers,
Martin.
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If it has a slate DPC (which usually works or can be made to work) why does it need an injected one (which doesn't) ?
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am i right in believing that this is more or less floor to ceiling ? I was always led to believe that rising damp gets about 2 foot up the wall and hacking off to a metre high is the done thing. I would suspect penetrating damp more than rising - are both walls exterior and rendered ?
Regards Jeff
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     snipped-for-privacy@geocities.com (Martin) writes:

By what means have you deduced it's not condensation? Damp up near the ceiling is either condensation or penetrating damp.

You have to accurately identify the cause of the damp before thinking of ways to fix it. If you've done that, you haven't said here, and it's necessary to know before advising how to fix it and how to replaster afterwards.

That starts by correctly identifying the cause.
--
Andrew Gabriel

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If your wall is damp above about 3ft, IT IS NOT RISING DAMP, and a DPC has nothing to do with it.

They obviously dont know what they are doing and are relying on your ignorance to RIP YOU OFF!!!
The damp could be falling from within a foot of the coving, which suggests that it is coming from above. It could be Gutters, Overflow Pipe, Rotten Window, Shower/Sink/Bath/Central Heating etc. Leaking, and so on - but it is not rising damp!!!
Unless your covings are only 4 ft from the floor/ground level.
--
Richard Faulkner

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Martin wrote:

Check your rendering. Check it again. Look for cracks, tap it to see whether it sounds hollow. See if there are cracks around cills where water could be getting in. Is the render painted? I've had a few similar problems in the past.
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Chris Bacon wrote:

walls
walls.
The age of your house suggests that it has solid 9'' walls, was the outside rendered to try to cure the problem ? does the damp worsen after bad weather? old or blocked guttering may be overflowing on to the wall side and getting behind the render, we had a simmilar problem with water getting behind paint, once the paint was stripped away there was a damp patch of about 8 square meters on the outside wall, its just about dried out now ,about 7 months later
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snipped-for-privacy@tesco.net wrote in message

Hi All,
Good replies and questions as usual. Apologies for this long reply!
Contrary to one reply I don't regard myself as ignorant!!
Here is what has been tried.....(deep breath)
- Render is good. No cracks and painted. No knowing if it was applied to try and cure the damp. The only problem I can see with the render is that it has no bellcast on the bottom. I've no experience of bellcasts but it makes sense to me. -Gutter is good. Works with no blockages or leaks. -No damp in the room immediately above the affected area. Recently took it back to plaster and it was bone dry. -The only source of water above the affected area are some central heating pipes. I've had all the floorboards up and there is no evidence of previous leaks or current leaks. It's all dusty dry. -No water tanks or pipes in the loft. -No water pipes in the walls. -Damp has been a problem for some time. Replaced with double-glazing approx one year ago. This has had no effect whatsoever. I've sealed it up very throughly. No evidence of damp immediately around window when I removed the old unit. Sash windows must have been fitted originally. The gaps where the weight boxes would have been have been replced with timber. These were bone dry and had no evidence of water damage. -I've tried the old mirror trick and no condensate formed on the mirror. -When I replaced the window some of the least accesible brickwork was noticeably damp. -The metal inserts used to get a good corner on the plaster and a couple of socket back boxes are rusting as well which indicates to me that it's not condensation. -I was told the same thing about rising damp being only able to get a few feet up the wall but it doesn't change the fact I have damp to approx 8ft. -One builder and two damp companies have agreed the exterior render (painted by the way) is in good order. -Wall are solid 9" with no cavaties. It used to be a commercial property but was converted to residential in 1988. -Someone feel free to correct me, but I heard that slate dpcs fail after a time. This one is 135+ years old so I'm not expecting it to be that good. -Both walls are exterior and rendered. -Weather doesn't seem to affect the levels of damp - I experimented over the summer. -There is some paint bubbling on the outside when it rains (approx the size of a dinner plate) but this approx 10ft from the worst affected area. The rest of the paint seems to be stuck fast as is the render.
So the question remains (one I've been trying to answer for some time) is it rising or penetrating damp. I see no way it could penetrate the walls so it has to be rising damp? The only weird thing is it's almost up to the ceiling.
I do have another couple of damp companies coming around to give me a quote - it's going to be interesting to hear what they advise.
Any advice suggestions would be most appreciated. Someone did suggest moving but that's not really possible at the moment!
Any experience of bellcasts on the render solving problems would be good to hear. It does sound logical that rain hits the wall, runs down and soaks in immediately above the silicon (and slate) dpc. A bellcast would prevent this and theoretically involve only a small outlay of time and expense to try.
Cheers,
Martin.
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Make sure that they are members of the BWPDA, (www.bwpda.co.uk).
Ask them how damp could rise above 3 ft, when all theory says it cant.
It may be worth paying for someone to take a core sample from the brickwork to see if it is damp in the wall, and not just on the surface.
Many damp companies dont know what they are doing, and tell you something needs doing when it doesnt.
Are you anywhere near Manchester?
--
Richard Faulkner

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Martin wrote:

-There is some paint bubbling on the outside when it rains (approx the

on our wall there were a few patches of bubbling paint the majority of it looked fine, once removed though the wall was damp over a large area which had been covered in 'good' paint. one of the problems was the previous owners had used a rubber based paint half way up the wall (to cure the damp) so the water couldn't evaporate once it had got behind the paint, as someone said earlier any paint used should be breathable. Could you scrape a patch of the bubbling paint away to see if the render is damp underneath any water can travel a fair distance before it finds its way in.
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Hi Martin.
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 http://www.periodproperty.co.uk/cgi-bin/discussing/forum2.pl?#43991
Now, whats going on:
1. Vic houses handled damp fine when they wre built, they were not pits of damp. So the basic design is good. 2. Since its damp now, it is what has been changed that has caused it.
What has changed?
1. Airtight double glazing stops ventilation 2. Chimney blocked off 3. Maybe draught proofing elsewhere too 4. Gysum plaster and emulsion 5. Cement render and paint 6. 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: 1. More damp is produced inside by breathing, cooking and showering than comes from outside 2. Thus what is wanted is porosity, to allow the damp out, quite the opposite of sealing. 3. Damp proofing companies do work so they can get your money. 4. If dealt with appropriately, a Vic house with no dpc, no render, no waterprofing treatments etc can be dry and healthy. 5. 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.
NT
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snipped-for-privacy@meeow.co.uk wrote:

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.
Edgar
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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.
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Stuart Noble wrote:

are
it doesnt blow the theory away at all.
1. I have not observed that to be the case, although of course it will be in some properties 2. A summer shower sends the RH up to 100% rapidly, inevitably increasing the odds of condensation. 3. There are many buildings with penetrating damp problems, which will fit your above analysis. Many of course have both penetrating damp and condensation problems. 4. see below about how this can cocur

that may be why 'any amount' wasnt suggested

damp
Another classic misconception there. As air exchanges between a warm house and cold exterior, 2 things occur.
1. 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.
2. 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.

Replacing
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.
NT
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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.
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Then the chances are you're not heating and ventilating the house properly in the winter.
If you choose to try and save money in an old house by blocking up ventilation to try and save on heating bills - and don't keep the temp up - you'll get damp. Best to change to a cheaper well insulated modern house designed to work like this - and just put up with the lack of space.
--
*Where there's a will, I want to be in it.

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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Stuart Noble wrote:

good.
water
what are you talking about?

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

on
avoid
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.

Clearly this is a waste of time.
NT
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Does 30 odd years of practical experience count?

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.
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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.
--
Andrew Gabriel

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On Wed, 13 Apr 2005 09:56:30 GMT, "Stuart Noble"

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.
cheers, Pete.
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