Vandex disaster

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pasty77

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Our barn conversion was done back in 2004. Building control insisted that the whole building was tanked in Vandex which seemed crazy at the time aside from a few downstairs areas but we had no choice. Our builder had never used it so sought advice and was told (I don't know who by) that you can apply like render and paint directly onto it. I believe it was the BB75 I keep reading about. We spent weeks taking out all the old pointing (walls are devon stone / slate / shellet) and then it was rendered I guess with cement and then the Vandex was applied in 2 coats I think). It gave us a finish we were sort of happy with (we wanted a rustic finish like a heavily limewashed only wall). So we got on and painted it with emulsion. Speaking to a few builders since I'm guessing most of you know what's coming next. Damp and mould. Serious black mould. Every winter, if we put anything within an inch of a wall we quickly get mould behind it. We have tried anti-mould paints, a dehumidifier, cranking the heating with the windows open etc. etc.

We went on holiday for a week last winter and the boiler went wrong. When we came back the walls were black. So it's not only moisture generated from us / washing etc.

Now, my guess is in the winter, the walls (single skin) are getting cold and acting almost like glass as they get soaking very quickly. Any interior walls are immune, it's just the outside ones. As the surface is waterproof, it's acting like a condensing panel and then the inevitable happens.

Needless to say I am not happy with this. It's horrible to look at never mind the health effect on our family and furniture etc.

Anyone got any ideas on the options? Can we re-coat with something else? Do I need to hack it all off? Some places we have dry lined with plasterboard which has solved the issue but as it's a barn there are lots of bendy walls, windows, timbers and lintels etc. so it's not simple.

I don't blame the original builder, he's a good guy and was only acting on advice he had been given.

Help!
 
Welcome pasty, you've come to the right place. Some one will give you the science behind why that failed. I've never heard of vandex used this way before, used it a lot over the years, swimming pools , basements etc never had a problem. Hope you get it sorted :RpS_thumbsup:
 
It should of been vandex first on the bricks, brushed in covering every little bit,two coats of this, then rendered on top in my opinion, options now, i think are building a mf wall in front ,putting a damp membrane behind, insulating between mf studs, fitting moisture boards and skimming, if you have the room, single skin is a nightmare, everyone involved needs a kick in the a, sorry for you..
 
sounds like you need to hack all the cement of let moisture out re render with lime mortar ,several other breathable products also just get some one who knows what there doing
 
Where are you based @pasty77 maybe someone on here can come and have a look for you. Lots of solid tradesmen (and women) on here.
 
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Black mould is a condensation problem not damp coming through the tanking.

I have done this when it has been spec'ed, not with BB75 but other tanking products. Normally in a plant room below ground. 1 10mm coat of SBR modified render, then 2 coats or tanking. The builder then paints with a masonry paint. Its fine if warm and well ventilated.
 
Wow, thanks for all the quick replies. It's deffo condensation. It's quite a small barn and we weren't allowed to do much with windows etc due to planning restrictions. We have the heating cranked up and ventilate as much as we can. Our moisture meter reads 70 or 80 most of the winter. There are 5 of us living here with a dog but as I said even when we weren't here, the place went mouldy. It seems to me that there is simply nowhere for the damp to go and the walls act in the same way as a window, the damp in the air condenses on them. I've been told it's ventilation before and that just got frustrating when we explained the lengths we have been to. Our dehumidifier filled up as fast as it could.

As I said, boarding the place is mostly impossible due to bends and curves in the walls and Also the house is very narrow as it is.

What annoys me is that I doubt upstairs even needed doing. All the houses around here are the same construction and have never been tanked upstairs with no problems.

Im in south devon by the way. The only problem with someone coming out to look at it is that we couldn't afford to have it sorted professionally right now. Any labouring would be done by me. Just being honest.

A guy I know says I should cover the vandex with a lime plaster and that will largely solve the issue. Anyone agree with that? I'm thinking I might try it in one room.
 
I should add that these are the interior walls I'm talking about. The outside of the building is left in natural stone.
 
Sounds like condensation damp to me. Nothing to do with tanking that will only stop penetrating damp from the outside in.

I'm using The Plasterers Forum Mobile App
 
The cheaper solution might be a positive input ventilation or PIV for short have a read here this may help your situation and welcome to the forum.


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It is possible that the condensation moisture is more concentrated to the very surface as it has the vandex on there where as usually the surface is porous and the damp may not appear as bad as it actually is until the moisture content builds to a high level.

Rendering in your case won't stop the damp but it may reduce the appearance and the mould.

Internal Condensation will always be drawn to the outside surface where it is cooler

I'm using The Plasterers Forum Mobile App
 
flynnyman said:
The cheaper solution might be a positive input ventilation or PIV for short have a read here this may help your situation and welcome to the forum.


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I think your missing a more obvious solution flynnymarra.............................:RpS_wink:
 
Artisan998 said:
I think your missing a more obvious solution flynnymarra.............................:RpS_wink:
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Please do tell. My thinking on this is that the air in the building is becoming damp due to humans / animals etc. the damp air had no good way of escaping / drawing in drier air as the walls cannot breathe any more like they used to. We have effectively water-proofed the walls so no damp can escape so any moisture stays inside and condenses on the coldest surfaces ie. the walls which are hard and impervious. Or is that flawed thinking? We do have some areas upstairs which we left as stone, just pointed with lime and no mould ever appears there. If we had done that over the whole upstairs, what is the worst that could have happened?
 
Pasty77 .... I no it's painfull but plaster in fat lime and re point in lime ...what goes in must come out
 
Olican said:
I've done a couple of barn conversions around there, Beenleigh was the last. Done slot in Diptford as well, nice neck of the woods.
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You didnt do this one did ya olli...........................:RpS_unsure:
 
Warm moist air will always be drawn to cold air in this case the inside moist air drawn toward the cold outside air. Its natural occurrence.

Moisture from humans and pets does add to it but that's not the real issue it will happen anyway.
In many solid wall cases people simply have to put up with some level of it.

Solid wall construction is problem but it was done and we were left with widespread interstitial condensation issues

I'm using The Plasterers Forum Mobile App
 
PS the air isn't 'becoming' damp. All air carries moisture to start.

I'm using The Plasterers Forum Mobile App
 
Olican said:
I've done a couple of barn conversions around there, Beenleigh was the last. Done slot in Diptford as well, nice neck of the woods.
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Beenleigh is in our parish, about 2 miles from me. Was it the farmhouse? Not been there for ages. Kids go to Diptford school.
 
He is on about vents pasty77 he is obsessed with them ;) he thinks it's the solution to everything. You have said you used emulsion you haven't used silk have you? Is it carpets or stone floors? Try putting the toilet seats down, empty the kitchen sink, don't dry clothes on the rads, dry the dogs, don't hang wet coats in the house, open windows, have you got curtains or blinds?
 
seanlar said:
Putting lime plaster over vandex it's a waste of time and money start again am afraid
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You mean get the air chisel out again? What a waste of time and money. Bloody building control. My instinct says that we should get back to stone and just lime plaster it. Like in the old days so that it breathes in and out. Or will that give me the same problem? I have lived in stone and cob houses all my life with just lime and we never had this even if it was a bit damp but you could usually force damp out with a good bit of heating as long as the building can breathe.
 
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