Lime Plaster & Clay Paint - Help needed!

[nic.w]

A skim is always pointless, and won’t work without an adhesive. Which defeats the purpose. And even if it would, you’d be hiding the symptoms not solving the cause. Once all is said and done, patches can be filled easily enough.

I still expect there was a lot of saturation, and plastering, certainly top coat shouldn’t have been done so soon. Sometimes just the nail/knuckle test isn’t enough. This is a conversation with your plasterer really.
Also a touch worrying that they wouldn’t turn you away from a paint which is all marketing deception and may not cause issues on some plaster, but here is clearly showing the issues that a vinyl bound product cannot deal with compared to a finish that allows liquid moisture movement freely.

That said, what was evident smell/colour/salts wise in the 6months before painting?

That’s a decent thickness wall to dry out, if you believe the rule of a month per inch then you’ll have an idea of when the fabric will be ready to act as an insulator rather than a conductor. Although, dry enough for plaster to go off won’t be as long.

What needs to happen is the moisture within the wall to escape find its happy dry equilibrium. Whether that’s feasible with the Earthborn layer I wouldn’t know. And how easy/possible it is to remove the paint, which may have bonded/penetrated the top coat…?

Thank you.

I will definitely leave the wall now for the winter at least and see what happens - whether the wall appears damp or not. It has been 18 months since the wall was gypsum plaster and membrane was removed and hopefully the wall could have dried a bit from the outside!

Before painting the smell was there but there were no salts.

I doubt I will be able to remove the paint without damaging the plaster further unfortunately. What product would you recommend filling patches with if / when I give it a go?

 

[a twig]

Just to provide potentially some reassurance on my experience using Earthborn clay paint on problematic walls (I re-plastered and re-decorated inside before I’d repointed outside and water was coming through) - it worked well and there were no issues with bubbling etc despite the binder.

After heavy rain you’d see darker patches in the paint as the moisture came through which would then lighten as the moisture was released and the wall dried again. I’ve also used it to paint lime plaster before it had quite finished going off when in a rush to get a bedroom finished and it merrily allowed moisture out and indeed happily effloresced salts out around a troublesome window and chimney breast.

My issues with Earthborn were more around quality control, having used 10 or 12 large tins over the course of 7 years, 1 or 2 were definitely “bad” tins where the colour was off and the consistency was odd - you may have just been victim of a bad batch.

An alternative route I went down in one room was to limewash the walls to get some level of finish on and still have maximum breathability, heal any small cracks etc then go back and paint over it 6 months later once I was certain I had resolved the root cause of the damp issues

 

[a twig]

Sorry, one other thing from your first post. Having a dehumidifier and also ventilating is counter-productive as you end up trying to dry out a constant inflow of outside air.

Don’t suppose you have any photos of the wall before the plastering was done by any chance?

 

[Kearn]

Thank you.

I will definitely leave the wall now for the winter at least and see what happens - whether the wall appears damp or not. It has been 18 months since the wall was gypsum plaster and membrane was removed and hopefully the wall could have dried a bit from the outside!

Before painting the smell was there but there were no salts.

I doubt I will be able to remove the paint without damaging the plaster further unfortunately. What product would you recommend filling patches with if / when I give it a go?

It’s an odd one, although I doubt that rainwater pipe running behind the wall is entirely innocent.

It’s not a normal place to have tanked internally, on a 1st floor. I can’t imagine there wasn’t an issue, maybe since resolved, that someone was trying to deal with. Might be the remnant of that, maybe contaminants, maybe the paint has stained/moulded hence the discolouration rather than just dark damp patches.

lime can act as a poultice, which is maybe why the inside is showing issues even though drying can happen through the external face. 14”” is also a long way to travel when there’s a closer brick face.
There’s definitely salts being brought to the surface, which definitely cannot escape through the paint layer to be brushed off.

It’s all conjecture though…

There’s every chance the top coat has been compromised anyway, especially if you say it’s brittle. I’d probably scrape off paint and top coat as one, should detach from the float. Then see what happens before the next step.

The smell is not dry plaster. Regardless of whether we think things look/feel damp, doesn’t mean they aren’t. So it sounds as if you painted before it was dry.

Just spray some old bricks and mortar with a hose, or any bare daub/lime with a hand spray and the smell is instantly recognisable.

 

[elizabeth]

Just to add to the Earthborn comment, we used the paint on a problematic wall and had to scrape the whole lot off as the wall started to look like we had sprayed it with a light mist of oil which looked a mess. I sadly took off the fine skim with it as it was very hard to remove just the paint. If I tried to sand the paint away, it just developed a hard shine and was untouchable.

I’m sure leaving it to dry out, brushing away the salts, and using limewash, which we reverted to, will be the best way to go. At some stage we will fill the accidental dips I managed to create with my scraper.

 

[Kearn]

Just to add to the Earthborn comment, we used the paint on a problematic wall and had to scrape the whole lot off as the wall started to look like we had sprayed it with a light mist of oil which looked a mess. I sadly took off the fine skim with it as it was very hard to remove just the paint. If I tried to sand the paint away, it just developed a hard shine and was untouchable.

I’m sure leaving it to dry out, brushing away the salts, and using limewash, which we reverted to, will be the best way to go. At some stage we will fill the accidental dips I managed to create with my scraper.

In small areas, just go with polyfilla, unless you happen to have putty or a pre mix superfine to hand. It won’t do any harm in tiny doses.