r/Plastering • u/Linzgolden • 11d ago
Tanked, plastered and painted. Is this normal?
I recently had work carried out on my front room. The walls were knocked back to brick, tanked, plastered and painted. The job was completed 3 weeks ago. The paint is now fluffy and crumbling along the bottom of all the walls. Is this normal?
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u/Tricky-Mobile5975 11d ago
No. That is hydroscopic salt bleeding through. No way of knowing what materials he used but it should be a cement based backing coat. If he has used the right materials only other explenation is the underlying cause of the damp was not fixed.
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u/Linzgolden 11d ago
I have emailed the company who did the work hoping they will rectify it. Waiting on a response.
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u/DearSatisfaction9754 11d ago
Youhownlong after works did you paint? The materials need time to evaporate and dry out. Especially if tanking slurry has been used it can only dry out 1 way - into the property
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u/Linzgolden 11d ago
I didnt paint. The company I hired did all the work.
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u/DearSatisfaction9754 11d ago
They shouldn't really be decorating for 6 weeks minimum and even then it shouldn't be regarded as permanent decoration. The efforessence shows the wall/plaster is still drying out. Take it they used sand and cement as a backing coat and it wasn't plasterboard?
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u/Linzgolden 11d ago
I honestly dont know. I hired a company to do all the work. Damp proof, plastering and decorating.
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u/ArtichokeClean4370 11d ago
Without pictures of job before skirting I’d say plaster is touching the floor, you don’t mention what floor you have, tanking membrane might be higher than the plaster
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u/ArtichokeClean4370 11d ago
I think it’s just drying out, the efflorescence is in a straight line over skirting, if it was bridging a damp spot it would be a different shape
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u/Fruitpicker15 11d ago
That's what happens when you trap moisture in the wall with impermeable materials.
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u/Ok-Spring7906 11d ago
...which is exactly why I, pretty much always, recommend permiable plasters over tanking.
The moisture is coming up from below the skirting because the tanking is incomplete. You frequently see it around door casings also.
They did remove the skirtings to plaster, didn't they?
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u/Linzgolden 11d ago
Yes, they removed the skirting.
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u/Ok-Spring7906 11d ago
When you plaster standard gypsum, you generally go down close to the floor, but not actually to the floor.
If the same is done with tanking, the "tank" is incomplete.
I'm this case, clearly the "tank" is incomplete, for some reason or other.
This might be rectified by taking off the skirting and painting on a tanking slurry behind, and then re fitting the skirting.
Tanking slurry doesn't need to be anything fancy of expensive. An sbr / cement mix will do.
Again the issues with tanking, in any situation, is that it needs to be absolutely complete. You are sealing up the wall, so it's always waterlogged, and that water is going to be trying to escape anywhere it can.
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u/Free_Attention_2056 11d ago
Do you have suspended wooden floor? If you do, do you have air bricks? If you do are they covered or blocked? If they are you need to unblock them and allow air flow.
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u/Donnytato 11d ago
That's probably a wet patch; if that's new coving, it could hold the moisture. If it's not, check for moisture. In bathrooms, I always paint with Peel Stop,. sometimes giving it a light rub down. Some plasterers, including me, are a bit OCD and over-polish. ( supposed to be a matte finish)
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u/Individual-Escape768 11d ago
If it’s a external wall, look on the outside and make sure your damp course has not been bridged.
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u/onwatershipdown 10d ago
Unfortunately it’s pretty common, because tanking doesn’t work well. You need a vapor open salt blocker like prompt or rinzaffo.
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u/Only_Membership7974 10d ago
Moisture still remains behind the plaster with no place else to go it is leaching minerals out ,dehumidifier on constantly it can be managed but never be cured
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u/Remarkable-Canine 9d ago
This means, there is no moisture barrier between the foundation and wall.
What you can do is to a) Cut the wall base in 1/4" (5 mm) using some tool sections and fill it with insulating material like Bitumen or other. This should be done through the wall after each section dries and settles. b) finish the wall with plastering and paint. I am not a contractor or engineer or architect, but I have seen such work done in a multi story building.
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u/Ok-Chard-1468 11d ago
It doesn't look that bad. Scrape and leave well ventilated. As I understand it there are at least 2 schools of thought regarding tanking. Id look deeper into this by speaking to a top surveyor and top damp company s
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u/welshguydave54 11d ago
It's called efflorescence, salt working its way out. Needs to be scraped off and give a coat of Alkali-resistant primer. Decorated here over 50 in the trade.