How much wet can condensation cause?

[vicky whitworth]

My neighbour has a sodden carpet along one wall but in two rooms of his random rubble cottage. He is adamant the water is coming in from outside. Nothing has changed outside. There's water running down the lane outside the cottage but it's flowing away down a concrete channel. Inside the wall is 'tanked' with something he calls vandex? The carpet is soaking right up in the angle between the wall and the concrete floor. It's a wool carpet with wool underlay. The change inside is the carpet is new. It was nylon carpet tiles. I think it's condensation. He's asked my opinion. He's sealed up everything with a variety of modern potions. Could condensation make that much wet?

 

[Zebra]

Don't know but it sounds nasty, and a good argument against tanking. If the walls were tanked, what was done with the floor to protect from moisture coming in? Is it coming up through the floor? Is the join between the floor and the wall poorly done? How long ago was it tanked? Perhaps the nylon tiles were hiding a problem that was there all along. If it were condensation why would it form there in particular rather than anywhere else? Is that area colder than anywhere else?
My walls used to be tanked, and the moisture which wicked up the walls somehow found its way in, perhaps through cracks in the cement, and when I stripped the glossy thick paint off the interior walls last winter, there was water running down the walls inside. Now the tanking's all gone it's perfectly dry.

 

[LadyArowana]

Is the wet patch smelly, and does he have a dog?

 

[JoceAndChris]

Without knowing all the ins and outs of his building it's really hard to know. It could even be water coming from an upstairs bathroom - like a badly sealed shower?

 

[Flyfisher]

I've never used a dehumidifier myself but I understand they can extract many pints of water from the air each day (can anyone confirm this from personal experience?), so I suppose condensation could be the source.

But I agree with the previous comments; if it is condensation, why is it being concentrated in this particular location? I certainly wouldn't dismiss other possible causes.

 

[CliffordPope]

Condensation can certainly produce a lot of water, and once started it is like a chain reaction, because as it evaporates it makes that area of wall colder, so you get more condensation, and so on.

Condensation will occur at the coldest points. So if the wall is coldest at ground level, or below, it will produce damp in exactly the same place as would water leaking through the wall. Also the two can be linked - a little bit of incoming damp cools the wall, triggering condensation.

Yes, dehumidifiers can remove gallons of water. Leave one on in a room that has been flooded for example and you will be emptying the reservoir several times a day.

It's often hard to distinguish the source of water. Sometimes if you pull back all carpets etc and wipe it dry, it's possible by very careful looking with a good light to see whether water is seeping in, or dampness creeping. Or try drying off the surface with a fan heater and then watching to see where any returning dampness is coming from.

 

[vicky whitworth]

The dog was blamed in the first instance but the wetness is all along two walls (total length, maybe, 8 metres). They have condensation problems elsewhere - in those dark corners behind wardrobes and behind the telly but these are on the walls rather than the floor. The vandex was run down the wall and then turned under about 8 inches. The wet doesn't appear to be coming up the join between the edge of the vandex and the concrete floor. It's more tucked back against the wall. It's a north facing wall with no windows the entire length. The cottage sits on the spring line, there's lots of water about. It's Devon. They have no door on their kitchen into the rooms that have the wet and they do lots of cooking. They have a shower downstairs as well. Oh and plastic double-glazing. They are really worried about it.

 

[Penners]

Judging by my quick Google search, Vandex makes a variety of tanking materials, so obviously the wall has been coated with one of these damp exclusion sealants. The problem with this kind of treatment is that it does nothing to cure the source of damp. It just (sometimes!) prevents the damp from appearing on the interior wall. So that makes it even more difficult to ascertain the source of the damp.

If your neighbour's problem was being caused by condensation, I can't help feeling that this would be very obvious - it would be possible to run your hand along the wall and feel, even see, the wetness. And it's unlikely that the floor would be creating condensation, given its insulating layer of underlay and carpet.

Is there any apparent cracking where the Vandex meets the concrete floor, or in the Vandex wall itself?

If nothing of this nature can be found, I think my approach would be to remove the carpet and underlay from the affected area. Roll it back quite a way, so as to leave the wall and floor fully exposed along that wall. I'm afraid this may mean getting a professional carpet-layer in to relay it later, but I can't see any other way of getting to the root of the problem.

Having exposed the affected area, I would then keep a very close eye on it for some time. Inspect it several times a day. In particular, watch it during wet weather (judging by your reports of water running down the street, this could be a factor). It may help the observation process if he lays a line of something absorbent, such as blotting paper, along the wall/floor joint. This will show dampness very obviously, and as soon as it appears he can carefully study the place where it is most apparent.

One further thought - what abuts the wall outside? Is there, for example, a pavement or tarmac right up against it? If so, does the camber of the road lean towards his house?

And finally, did the Vandex treatment come with a warranty that is still valid? If so, perhaps your neighbour should be chucking the problem at the installer.

 

[MdB]

In past history, my old wall was deemed to be damp so had a layer of tanking placed on it and then the wall rerendered and then painted. A while later, the wall was still deemed to be damp so it was tanked again, rerendered again and repainted again. Unfortunately, it was apparently still damp so a third layer of tanking was applied, more render and more paint. A while later, Mrs MdB and myself purchased the property and found that this same old wall was suffering from damp and hence needed to do something about it. Fortunately, I had found this site and after some discussion I decided that applying a layer of tanking may not be the best solution and removing the rendering might be the solution. On removal I found the three layers of tanking (at least!) along with at least 5 layers of cement render and plaster. Total thickness was over 150mm in places. When I got back to bare stone, the wall stunk due to the moisture trapped behind all the layers. Fortunately this smell and the moisture disappeared once the render was removed as it could now evaporate off and I now have beautiful and dry stone wall in the living room.

You may not be surprised to know that tanking is the last thing I want in my house.

 

[stuart45]

I had a similar problem in our kitchen. I ripped the bottom 3 ft of plaster off, and there was enough thickness to build it back up with thin stones and lime flush with the plaster above. Never had any trouble since, and my wife prefers the stonework to plaster.
I would say that 99% of people that I've worked with in the trade would still use tanking or similar methods to cure damp problems. For years I thought it was the way to do the job.

 

[MatthewC]

One further thought - what abuts the wall outside? Is there, for example, a pavement or tarmac right up against it? If so, does the camber of the road lean towards his house?

That was my first thought as well. I would also ask what level is the ground outside the wall, compared to the floor inside? 4" to 6" clearance (floor above ground) is good - in places mine was 5" the wrong way round! If it's earth, dig down to expose more wall and see if that makes a difference.

 

[Keithj]

... and French drains are a wonderful (and simple) solution to many damp problems.

I have been surprised at just how much wet can be in humid air. We have a large "picture window" in the hall - leaded light (sadly not artistic). Since it made for a very cold hall, we had a secondary glazing (placcy) panel made to insulate it. That pretty much solved the heat loss problem. but the inside of it misted up very quickly. The gap is about 1½ inches.

I "happened to have" a large supply of heavy duty moisture absorbent (tropical, radio equipment for the keeping dry of). I made up a cloth sausage containing 300 grammes of the stuff, which I thought would be enough. It cured the misting for about a week. When I took the sausage out again, the weight was a shade over 400 grammes. I dried it (back to 300 grammes) and put it back. Within a week, it was misting again.

During the summer, there was no problem. Now, I'm back to weekly fixes - that's over 100cc of water in a space roughly 1½ inches by 40 by 30. Rain doesn't get in - this is just moist air, presumably sucked in and out of the air gap as temperatures change.

 

[tobydog]

Good timing. I've been looking at getting those plastic secondary glazing units that sit directly over the window frame by way of magnetic strips. The idea was to sort out the cold and eliminate the condensation. It now looks as though the condensation theory has been shot although our windows are quite tight.

Since I started using the dehumidifier we no longer have condensation on our lower east facing wall. It was running wet just a couple of months ago but now nothing. The unit took a couple of weeks of 2 hour daily sessions to get rid of the excessive moisture in the fabric of the house and now I use it for 2 hours every two or three days to keep on top of it. This has significantly improved the situation in the house and even when a bad night causes condensation on the windows it dries up quicker. We still have a problem in the main bedroom but that is more of a ventilation issue. The unit runs at 55-60% RH and anything lower than that feels too dry. I don't know how people can run them at 40%.

Looking at this thread, I'm firmly in the camp that it's excessive moisture / water coming through the wall or floor. I've lived in some very damp and badly ventilated places but I've never had soggy carpets.

 

[Penners]

I've been looking at getting those plastic secondary glazing units that sit directly over the window frame by way of magnetic strips. The idea was to sort out the cold and eliminate the condensation. It now looks as though the condensation theory has been shot although our windows are quite tight.

I wouldn't be too hasty in dismissing secondary glazing as a significant contributor to the reduction of condensation. Provided (a) the inner glazing is an airtight fit on the window frame and (b) you make the outer (original) window as draught free as possible, it should be of some considerable help.

Draughtproofing the outer window should prevent the inner glass from getting too cold. Warmer inner glass should reduce the precipitation of moisture from the warm air inside the house.

If there is no reduction in condensation on the original outer window, then the inner glazing is allowing considerable air movement into the gap between the two glazing leaves. If there is no reduction in condensation, but that condensation has simply moved from the outer to the inner glass, then the outer window must be very draughty.

 

[tobydog]

Thanks Penners. I think those magnetic units fit quite snuggly so there shouldn't be leakage from the house into the gap. Also the 'glass' is made from some polycarbonate stuff which should also help cut down heat transfer to the gap. As I said, the windows are a good tight fit so I may be okay afterall.

 

[Feltwell]

Lots of old threads on secondary glazing Tobydog, including this one where I did the magnetic tape & polycarbonate system.

http://periodproperty.co.uk/forum/viewtopic.php?f=1&t=11602&p=149449&hilit=secondary#p149449

I still haven't got around to sorting that sash but, with lots of kitchen roll stuffed in the (large!) gaps round the sash, there is no real condensation problem that I've noticed. By rights, this ventilation of the gap to the outside should mean that I do get condensation, but clearly no one's told the water vapour.

Big panes (such as that main sash) do end up needing some additional mechanical fixings I found. Maybe just because the sash is in such a state, but when we have a storm the secondary glazing would detach from the magnetic tape at one corner. The smaller side windows, and sashes elsewhere in the house, are fine with just the tape holding them.

 

[Keithj]

I suspect that the condensation in our windows is caused by warm, damp air from inside the house being sucked into the "cavity" when the outside air temperature drops of an evening, and the moisture condensing out as the air cools.

A tighter seal on the secondary glazing may mean it draws in cooler, drier outside air. It is held in place by small clips, and has a compressible plastic edge to seal it - it's certainly not as airtight as the outer window.
I just put up with microwaving my desiccant sausage once a week.

 

[MatthewC]

I just put up with microwaving my desiccant sausage once a week.

Mind boggles! :lol: :lol: :lol:

(Had to make a comment on that one before Penners)

 

[tobydog]

Thanks Feltwell. That's really usefull. It's given me the confidence to go ahead with it. Our lounge is triple aspect with four windows and thin walls. Rather chilly so I will tackle the north and east first. The south is an unusal bay style window that protrudes from the house wall. It's three small sections so might need to work on that one.

 

[Penners]

my desiccant sausage

I do sympathise, Keith.


Matthew - I am the self-appointed bad joke maker on this forum, thank you very much.