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Plastering & Rendering

Lime plaster or just primer and paint over hairline cracks

Anonymous user 28/02/2024 - 3.44 PM

Hi. Please can some give me dome much needed advice on how to deal with hairline cracks in plaster and preventing mould re.occurring. 3 years living in an awful 1950 built property I unfortunately purchased. 6 months after moving in (springtime) i could smell damp but not see any mould. After heavy rainfalls the nasty wallpaper started lifting. I pulled up the lining paper to check... as you do... and found mould growing about 500cm high from the skirting board. Removed the paper washed wall down with mould remover. The paint work was/is cracked throughout. In my wisdom I chipped the years of paint off to find the cracks i saw throughout the paint work mirrored those in the plaster. I'm not sure of the type of plaster I have, it has a grey colour to it. There is also some chasing done where alot of the hairline cracks start from. The chasing (where the mould had grown right through the paintwork) looks like cement. Does cement attract moisture? The plaster was bone dry where it originally was wet or I where i could see a water marks on the wall paper. I don't want to put wallpaper up again... but with the wall covered in cracks will 1.2.3 zinsser primer and painting over with a matt paint show up the cracks. Should I use a lime based paint or re.plaster with lime plaster. I.ve read that lime plaster let's the walls breathe and attracts less moisture, could I skim over with lime plaster or would the cracks just appear with a skim because the base is already cracked? Due to the build year and not knowing what the original plaster and render contains the cost of removal would unaffordable for me if it has asbestos and encapsulation would be the best option. Is putting fibre mesh on and then plastering over with a lime plaster an option? I have chipped most of the paint off one wall (an outdoor wall) not sure if I should for the other wall (another external wall side) which also has cracks and mould embedded in the paintwork. When chipping paint off from around the window, which is also covered in mould I found a layer of gloss paint under lining paper and two layers of paint. Gloss paint contribute to mould as walls cant breathe? Also appears that the first layer is an emulsion paint (magnolia!)... would that contribute to attracting moisture... on the plus side at least I don't have rising damp. Desperate for advice before I start scraping pain off the other wall and painting. Thank you.

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5 Answers

Southwest Build

Rating: 5 out of 5

Exeter

Its hard to know without seeing, as its not rising damp I would guess that its a cold spot on the wall. moisture in the air will attract to the cold and then over time create a damp spot. this cant really be helped. Cement won't attract moisture and if you are looking for breathable paint you can use Dulux Supermatt as it has no vinyl in it. If your house is brick built you will be fine to prepare the wall and skim it. you only need to to make it breathable if the wall needs to breath. ie cob walls or stone work. More than likely good ventilation will solve this issue.

Answered7 August 2019

Anonymous user

Use breathable paint and let some air in the room

Answered5 August 2019

Anonymous user

without knowing what the walls are plastered with initially it's hard to say. Breathable paint won't solve the problem as it's only beneficial if the wall itself can breath. Age related cracks are pretty easy to sort out but would defiantly need to see behind them to see if the cracks are in the building or just age related/shrinkage cracks. The problem could be that the wall was intended to breath but someone has used an un-breathable product (like sand & cement, inside or out, or both) to try sort out an existing problem. you'd be wasting your money skimming a wall with lime if the wall itself doesn't breath. (gypsum and sand & cement don't breath) zinsser is good for stain blocking and giving a key to materials paint won't stick to but won't sort out your cracks. ultimately i'd say hire a professional to take a look before you start troubleshooting and wasting money. Without looking I'd say it's a ventilation issue caused by condensation running off your walls and gathering on your skirting.

Answered13 August 2019

Anonymous user

If it was mine is would drill a few20mill holes at a 45%angle to ventilate then pin insulated plasterboards directly over the complete wall and reskim that's the onely sure way to cure this and won't cost a fortune

Answered15 August 2019

plasteringprojects

Rating: 5 out of 5

Gillingham, Kent

Best thing to dovwouid be to expose the wall by taking it back to brick and treating with fungicide. Then install some vents top and bottom to circulate air and then render but using a proper water proofer (sika) not b-q stuff. And replaster. Aerate and circulate. Easy ....

Answered7 March 2021