Hi
Has anyone any experience or suggestions on what to use to seal an exposed cotswold stone wall? I have read previous threads on using a diluted PVA mixture and will probably go with this but I thought I would see if anyone had actually done this on a cotswold stone wall.
Thanks
Why do you want to seal it? If its an old wall, sealing generally makes them wetter, not drier, and is not at all recommended.
PVA certainly isnt suitable.
NT
It doesn't need sealing and doing so will cause severe problems in future. If you are having problems it may be the pointing is failing though.
Perhaps you can explain the logic of this. Not recommended by who?
PVA isn't sufficiently waterproof. If the wall is already painted, try a pliolite resin based paint. If not, copious amounts of Thomsons Waterseal or similar applied during a dry spell would be the best bet.
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Says who? Don't you think it would be more constructive if you made some positive suggestions?
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Stuart Noble wrote: Mike:
Mike. And the experts:
positive
he just did.
NT
No. Ask these guys if you want:
Me, for one. There are two house building strategies.
The traditional strategy was used until 19somethingorother and uses breatheable materials like lime plaster, stone, brick. Any water which gets into the material evaporates off in its own sweet time
The modern strategy using damp courses and impermeable layers like masonry paint, sand/cement render, PVA which don't allow any moisture into the material.
If detailed properly, both of these systems work well, but problems can occur when they are mixed up eg
Victorian brick building which has later been covered in sand cement render on the outside and gypsum plaster on the inside. Moisture gets in somehow, maybe cos the damp course is not of 21stC standard. The moisture can't get out through the sand/cement render so it gets out through the gypsum - which fails cos gypsum can't cope with getting wet at all
Your exposed Cotswold stone wall would I assume have been built in the traditional strategy and if you seal the surface with PVA or the like, any moisture which gets into the wall will not be able to easily escape and you will get problems like rising damp, bubbling and damp patches
If you want to seal the wall because it is dusty, then I suggest you make some limewater [1] and apply few thin coats. The stone will still show through cos limewater is almost clear, but it will stop the dusting
Anna
[1] Buy small tub of lime putty. Decant some into a larger tub with plenty of water. Mix well. Allow to settle. Paint with resulting clear liquid. Repeat until happy [2] [2] Rumour has it that in hard water areas, painting with tapwater will be just as effectiveAnna
~~ Anna Kettle, Suffolk, England |""""| ~ Lime plaster repairs / ^^ \ // Freehand modelling in lime: overmantels, pargeting etc |____|
PVA is quickly destroyed by UV exposure.
Stupid idea!
Why the need for sealing, is it suffering frost damage?
cheers, Pete.
So bricks and stones breathe, but cement doesn't?
After it's destroyed the Laura Ashley presumably. Damp is not trivial and the fact that we don't tolerate it in modern buildings is a mark of progress IMO. People before buildings I think.
None of these is impermeable to "moisture". We need to differentiate between water, as in rainfall, and water vapour which, being airborne, will travel through virtually anything. The outside of a house needs to shed water effectively but allow the passage of vapour which, fortunately, isn't that difficult.
Usually in the hope of preventing damp.
It gets in because the render cracks and water can pour through at a rate of knots. Why it cracks is IMO because it didn't adhere to the surface in the first place so it moves due to its own weight. Cracks invariably correspond to larger areas of blown render, though which came first is open to debate.
Because a disproportionate amount gets through the cracks rather than the impermeability of the cement.
Out of interest (and I really do mean that :-), what mix do you use for your pargetting? Do you use pozzolans? Pipps Cottage looks great and I can see why restoration is high on your agenda but trying to stop a brick built terraced house leaking like a seive is another matter.
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Self appointed experts
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I used to have a Victorian house and on the most exposed wall, no emulsion paint or paper stayed good for more than a couple of years. In hindsight I should have used limewash on that wall and kept the Laura Ashley for the other three. There's no point fighting a losing battle
PVA and masonry paint are effectively a layer of plastic so water vapour can't get through them.
And usually unsuccessfully
Agreed. And also cos the wall is built of brick and lime mortar which will move slightly. Sand cement render is hard and brittle and doesn't move, just cracks :(
Often I use 3 parts chalk, 1 part lime putty plus goathair. Until about 200 years ago chalk was used instead of sand around here. Why it went out of fashion I don't know, but it makes a lovely malleable mortar
Not much these days cos much of my work is on timber framed buildings which move around with the seasons and pozzolans make the mortar more brittle (and resistant to weathering). When I was working in wet and stony Wales I used pozzolans much more
Its the same matter actually cos both my timber frame and Victorian terraces were built to breathe. Luckily I don't have a plastic emulsion paint and Laura Ashley wallpaper lust. Pips Cottage has just turned bright Suffolk pink but I won't post any new pictures until I've painted black stripes on it so it looks just as wacky as it used to do 100 years ago
Anna
~~ Anna Kettle, Suffolk, England |""""| ~ Lime plaster repairs / ^^ \ // Freehand modelling in lime: overmantels, pargeting etc |____|
Thanks for the support. Actually the key people who I'd trust making this recommendation are the RICS special interest group on old properties as they see all the damage done by incorrect approaches.
My approach to old and listed buildings which I restore is simple - no sealing with PVA or other materials.
Can anybody tell me why I can't see any of Stuart's postings directly ?
1:1:6 does a little, but not enough for Victorian brick walls, 3:1 doesnt. Chalk does, granite doesnt. So not that simple.
you presume wrong. Millions of Vic properties are dissipating their moisture this way, and dissipating it quickly enough that no damage occurs to the wallpaper etc.
Victorian houses were dry enough 100 years ago, as they are today. The idea that houses were horribly damp a century ago is a popular misconception. Of course there would have been worse houses around, but of those still up today, most didnt have a problem. Some do now as a result of inappropriate modern work.
Cement render and gypsum allow vapour passage, but not enough.
I dont know why im writing this, you were given a good link and are only being a wally.
cement
its one cause
not always. cracks here that arent connected with blown areas.
Controlling damp in Vic teraces is not achieved by stopping them leaking, in fact that is moving in the wrong direction altogether in most cases.
NT
The link was to a bunch of precious luddites who are rather far up their own arses for my liking
Yeah, right.
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It is an internal wall and it is in a kitchen. I want to remove any (well almost any) chance of dust or debris from the wall onto work surfaces.
Steve
Anna, any suggestions where I can get a small tub of Lime Putty from?
Thanks!
There are quite a few places that supply lime putty now. Google for "lime putty" and you may find one within striking distance. It usually comes in 25litre tubs which is far more than you need but if you can find a builder who understands how to care for old buildings he/she will probably have some and let you have a small amount. Ring you local Conservation Officer and ask if he knows anyone local that uses it. As a last resort, you could use the hydrated lime that comes in paper sacks at any builders' merchants. Put a cupful in a tub of water, stir it up and leave for a day or two. Then use the resulting lime putty in the way that Anna recommended.
Isn't it a shame that Stuart is so rude instead of being willing to debate issues constructively. Some of us who use the Period Property forum really do know rather a lot about their subjects and are more than willing to share their experience. You won't find much enthusiasm there for ever using Portland cement, gypsum plaster or any surface covering that makes walls less 'breathable'.
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