Please help! Advice on blown plaster.

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Colm O'Donnell

Colm O'Donnell

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Hi everyone, I was wondering if anyone could help. My wife and I purchased a newly constructed home about nearly three years ago. When we moved in after a month or two, we noticed the plaster began to blow on one of the masonry walls. The builder kindly came back, chipped it back to solid areas and had it plastered again. This has now been happening every few months throughout the home, and even in the areas that have already been patched.
The builder doesn't know why this would be happening and we are at our wits end having to re-decorate each time and with a baby on its way, due in the next few weeks we would be grateful for any idea of why this would be happening. So it can be fixed one and for all.
It only happens on block work walls both exterior and interior facing, the stud walls are fine.
I have attached an image to show the extent of the room that was meant to be the nursery, you can see the area at the top left where it was patched before.
 

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Hard to tell from the picture to be honest but it looks like a paint issue on the window wall, newly skimmed walls should have a mist coat with a non vinyl paint like supermatt or contract Matt watered down a little.. From the looks of it the paint hasn't adhered to the new plaster so is pealing off..
 
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The spot on the top left can tell you more than the one over the window. H2O molecules might destroyed thecrystals in the plaster . Bad key helps too. Any of this symptoms ? When you say the plaster blows off , do you have any attached to the wall or is completely separate?
 
If it's the skim coming away from the backing it's probably because there is no key for it or its drying too quick. It's deffo a problem With the floating if it's happening on all the block walls, what has he floated the walls with?
 
If this is.a fairly new build only 3years old was it coverd by the N.H.B.C ?. If so get them involved to investigate the cause of your problem .There could be many fsct
 
Thank you everyone for your help, the walls were painted by the builder as this was the show house for the street. None of the walls have been wallpapered. Its the thin smooth plaster that separates from the wall, it bulges out, separating from the scratch coat, it eventually cracks and then falls off.
I'm sorry but I'm not sure what you mean by "what has he floated the walls with". They came back and found more areas that are blown as well, but they said they have never came across this before. The builder said he contacted the NHBC and they said just don't paint it for a while, but we have left areas that were re-plastered for months before painting and some have failed again, others haven't.
 
The floating is a term for the backing coat, it's the skim that has blown and it will be a lack of key and if he hasn't seen anything like it before o would be worried lol pull off the loose finish and put a pic up.
 
Colm O'Donnell said:
Thank you everyone for your help, the walls were painted by the builder as this was the show house for the street. None of the walls have been wallpapered. Its the thin smooth plaster that separates from the wall, it bulges out, separating from the scratch coat, it eventually cracks and then falls off.
I'm sorry but I'm not sure what you mean by "what has he floated the walls with". They came back and found more areas that are blown as well, but they said they have never came across this before. The builder said he contacted the NHBC and they said just don't paint it for a while, but we have left areas that were re-plastered for months before painting and some have failed again, others haven't.
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NHBC would of gave that advise and if they did they are taking the piss because nothing is gonna happen from now till when ever.
 
lack of key is the problem , there's so many plasterers out there who don't even rub with a devil float, once the house is finished it's forgotten about , some plasterers haven't been working long enough to know any different and i have had this argument on this forum before now and because it sticks at the time of doing the job its all good to them , not bothered it isnt going to last any length of time
 
Agreed. I've seen reskims fall off like sheets of ice revealing walls behind it that never looked like they have even seen a wet bit of skim. No bond atall. Don't trust PVA all that much tbh. Can't just rely on suction alone.
 
Could be key or if it's sand and cement backing coat seen it shrink alot depending on sand and thickness and blow the skim coat off
 
You need to find out what the backing is. That's your start point.


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just a thought, If its sand and cement backing maybe it could have been skimmed to early or maybe its got some washing up liquid in it
 
Niro06 said:
just a thought, If its sand and cement backing maybe it could have been skimmed to early or maybe its got some washing up liquid in it
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Done both & never had any blown.
If it's s&c it's either had no waterproofer in & sucked his stones off, or no key.
Most likely both.


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skim coat will also fail if it has been caught by frost. show homes are always built in a rush may have been plastered before the windows were fitted,
 
Too much additives in s+c and bad sand leaves a weak bond for skimming,also in good weather some cowboys skim the s+c the same day.it should'nt be skimmed until fully set and cured.
 
Jaysus never seen it skimmed same day!! They should be ran!!


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