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Damp in home!

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boogagirl | 20:46 Sat 15th Jan 2011 | Home & Garden
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I have damp in the hallway and front bedroom (both external walls). My house is stone and pebble dashed (some years ago) so have no cavity and cannot have a damp proof course. I wonder the cause of the damp. Could it be because the dashing is old and cracked and with stone underneath and no cavity the rain is getting in? Would the solution to this be painting the house with high quality paint? I have tried using an insulating paint additive mixed with my paint and it did work for some time however I notice signs of damp recurring (black on walls, chalky spots and wall damp to touch). I have a new central heating system so this is not the problem. The house is an over 100 years old, semi. There is no debris outside of property which would be causing problems. If anyone can offer me any advice it'd be much appreciated. Also I have found a company who offer an alternative to traditional damp proofing, if anyone knows about this and if it works etc I'd appreciate the please!!!


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A very likely cause is that it is condensation from the inside, not ingress from the outside or below. If my understanding is correct that you have a solid stone wall with no cavity and no insulation and the inside finish is right onto the stone, then when the outdoor temperature drops well below the indoor temperature the inside surface will also be quite cool due to loss of heat through the wall. Moisture in the air next to the wall (particularly in corners and low down) will be dumped as the wall cools the air. This will be exacerbated if heating of the room(s) with the cold solid wall is poor or intermttent (for example timed). The only way to avoid condensation is to heat consistently and well in order to raise the temperature of the inside surface of the wall. Also, internal ventilation between warm rooms will help - not external ventilation onto the wall (e.g open window in that room) because then the surface temperature will not rise as well. Additionally, particularly in cold spells, making sure warm air sweeps across the areas most prone to condensation (for example by a fan) will help. To seriously deal with this if you do not intend to heat well is to put insulation either inside or outside the solid wall - you will still need some heat to completely avoid condensation if you are living in the place but heat loss will be reduced.
Question Author
Thanks for that. What kind of insulation could I use? This is what the paint additive does, insulates the wall so when the warm air hits it it will not cause condensation. I realise that the chemicals used in the additive will wear off and I will have to reapply but am looking for a more permanent solution. Our heating is on as much as anyone elses really, like I say it's a new system and very effiecient.
First off, Boogie .......... you might have a DPC. About then, it was common to use a course of slates at ground floor level, or pitch (tar) to do the same job.
I guess the bedroom is upstairs, so rising damp is very unlikely there.

The other two main causes are condensation and rain penetration.
Condensation is a problem that can occur whatever the weather. Solid stone or rubble walls are notorious for this because they are very poor insulators..... to put it simply, they're always cold.
Rain penetration is another big problem, especially with wall thicknesses of around 250mm. Also, the pebbles are "waterproof" but the render almost certainly isn't.

I've had a lot of experience with remedial damp work.......... I'd be glad to give you a few pointers .............. trouble is, I'm due at the pub now, so I'll have get back to you tomorrow if that helps :o)))))
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Thanks for the reply Builder! If you could get back to me tomorrow it'd be great :)
I know these old houses are terrible for this kind of thing. Look forward to reading your advice tomorrow.
Is this an advert? - (website at end of OP)
Question Author
No it's not an advert, the website is the damp proofing alternative I had asked if anyone had heard of and if it would be suitable for me!! I only found the site today so don't know anything about it.
If you have been told that the paint provides thermal insulation then you have been spun a line. There are lots of coatings available that provide a very good barrier against water ingress from outside (and others not so good - beware) and these are often simply brush or roller applied - an end to any ingress of rain etc., well worth their price.

There are different ways for you to insulate thermally. Externally you would in effect put a layer of insulation (foam sheets are easiest) on and then cladding on top of that - this is not a small job but not greatly complicated and leads to lesser disruption than internal insulation. Internally you put on an insulation layer and then a finish - the easiest way to do this is to use foam sheets that have plasterboard on one side - a ready made wall finish. Again, this is not a small job but not greatly complicated. In both external and internal cases the greatest challenge is in dealing with any openings in the wall(s) such as windows and doorways.

Without wishing to upset The Builder, all condensation is a result of temperature differences between a cold surface and warmer air (which is in the process of cooling down). Dampness from the ground up is not weather related but ingress from outside through pervious walls is (unless you are getting spray from a fountain or waterfall).
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Thanks Karl. There is something in the paint additive that works, we were free of problems for several months and they did state that we would have to reapply it every so often. Here is the website However I need something more long term. It does seem related to the weather, as soon as we have heavy rain for say a week at a time, we notice changes on the walls. I tried a humidity gage for a while and the readings were ok, so would this still be condensation? The rest of the house including kitchen is fine, and I would expect to see condensation in there if it were that.
Apologies if I am wrong boogagirl, but we do get new posters coming on here asking a question, and it turns out to be an advert for their business. Sorry therefore if I misunderstood.
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No probs. Am just looking for into and feedback :)
Very briefly, condensation occurs when air cools on/near a surface and this will be most pronounced where the air does not move much (corners, behind things aggainst wall, cupboards, even in containers) so it dumps its moisture. The colder the surface in relation to the air, the more risk of condensation so when the wall cools more fiercely from cold weather then the risk rises sharply. A lot of different factors can influence the precise spots where this happens. If the surface is porous then the moisture will be absorbed and take longer to re-evaporate, an impervious surface (glass, tiles, vinyl wall covering, gloss paint) will not absorb the water but condensation will more readily appear on it. I would not expect you to suffer condensation/dampness anything like as much in the summertime when surface/air temperatures are much more equal inside and outside the house - it gets progressively worse as the outdoors gets cooler and it is more and more difficult to keep the inside surface temperature up due to heat loss to the outdoors. This is why insulation works and is pretty essential in order to live a satisfactory life in a heated home. Until then to an extent you have a choice between heated home and condensation or cold home and far less condensation (cold air, cold surface, minimal condensation - just everything slightly but evenly on the margins).
OK Boogie, me again.
Well, you should have a pretty good idea what's going on now, thanks to Karl's excellent analysis.
The bottom line is that the damp spots are most likely rain or condensation...... probably a bit of both in my experience. I guess Karl would go along with that too.
Houses of solid, dense masonry are the worst kind to deal with, I'm afraid. If I'm renovating one, I invariably treat all exterior walls by fitting an insulated timber frame wall inside each outside wall, with 50mm ventilated cavity. There are plenty of other ways of course. Easy when the house in empty, but disruptive for you. Simple DIY job though!!

External insulation would be wonderful ..... in short, timber fixed to wall, insulation between timbers, wire and render to finish......... then paint ...... like a new house!
(Bit more tech than that, but that's the basics.)
Also, the old masonry acts like the biggest storage heater in the world 'cos it's inside the insulation. Warm house, no damp, lower bills.

Alright, so much for the wishlist!
In the real world, all I can suggest is something like this ...........

DIY application, lasts for several years before needing re-applying, works very well.
I've had to use it in situations like a porous chimney stack where rain drips into the fireplace, and the client is too tight to have the stack rebuilt. Works a treat though.
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Thanks both. How expensive is the cost to insulate externally, I kind of like the look of my house as it's old, by doing this would it make it look new? Also what kind of price would I be looking at to insulate internally. We are due to have the house painted this summer so could I put that sealant on top of paint. Sorry for so many questions, just trying to find the most feasible option.
Yes, I know, the external option is really only if a house has no external interest architecturally. Probably only for bland exteriors where it wouldn't matter.
As for cost. As usual, impossible to say without a good look at the house Someone would have to be given a specification too, so they could price it properly. I've done it for myself, but never had to do it for a client. It may not even be possible if your roof overhang isn't enough.
I could guess that it might be 20-25k for a semi, with scaffolding, painting etc.

I would put the silicone on to the "porous" masonry sometime, maybe after a spell of dry weather when the masonry is dry enough to be receptive to the sealer.
It's not a membrane type barrier. It has to soak right in to all the nooks and holes. Then you can paint it.

Insulating internally, although disruptive, is a much cheaper option. You could do a room at a time to spread the cost. Cost per wall should be in hundreds rather than thousands, for a plain outside wall plus more for skirtings, wiring, windows, decorating etc. Ask a decent local tradesman to look at it and give you a better idea
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So would the best thing for me to do be waiting until the dry weather, seal house then paint it? Do you know if thermal plater would help inside too?
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Here is the link for thermal plater. This is the site I got the paint additive from which did seem to work as a short term measure. If you could take a quick look and give me your opinion :) Thanks.

You can never have too much insulation Boogie.
I'm afraid I've never come across this plaster. I've no experience of it. In your case, with no insulation at all, then it has to help. I can't say I was too impressed with the U-values given here .......... (U-value is a measure of the "strength" of the insulation. The LOWER the number the better)


I say that in comparison to "Celotex" boards, modern multifoil roll, or any of the other products we use today.
It looks like you'd have to put a hell of a thickness of this plaster to get anywhere near the low U-values we can get with "dry-lining".

A good start would be to go to a big Merchants like Jewsons, and ask in the office if they have any experience of it, or know of anyone who does.
I'm always up for trying new technology, but I just don't know if this is offering any more than the better known products.
Question Author
Ok I will investigate!! Thanks so much for all your help & advice :) Very much appreciated. I just can't wait for the summer! ;)

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