Recommendation for breathable filler

[keithevans595]

Last year with advice from this forum I had part of a downstairs room replastered with lime putty plaster and solo lime plaster supplied by the Lime Centre.
It was left to dry out and painted with Earth born paints, in particular the feature wall is a dark green and the other walls a light green.

All was well, but a month or so later random patches of the feature wall, dark green, started to show darker patches like they were damp.
I thought they may sort themselves out over the hot summer but not so.

I have tried playing a gentle heat from a fan heater on them and they do begin to fade, but as the surface cools down they reappear.

One possible reason for the "damp" patches maybe that I blended in the new plaster to the old plaster with a very thin layer, max 1mm, of normal filler and filled in slight dips.
This may be why the patches are so random over the wall.

I think the only solution, and yes, I should have done in the first place, is to rub down the patches to get rid of the filler and apply a breathable filler.
Which brings me to my question, what breathable filler would you recommend?

Thanks in advance.

 

[Cubist]

Hi Keith,

Is it safe to assume the wall concerned is an external one?

Have you checked the wall outside for potential rain penetration of leaking/over-flowing gutters?

 

[keithevans595]

Hi Cubist,
No, the wall is an internal wall and is also a single skin.
The other side is in my neighbours living room and I have seen there is nothing on the wall that would cause the damp.

I think I used Polycel as the filler and am wondering if the filler is atracting damp in some way through the breathable paint?
All other areas of the wall have dried OK.
Hence I think the solution is to sand off the polycel filler and replace with breathable filler and paint, unless there is a different solution?

 

[Lacan07]

Last year with advice from this forum I had part of a downstairs room replastered with lime putty plaster and solo lime plaster supplied by the Lime Centre.
It was left to dry out and painted with Earth born paints, in particular the feature wall is a dark green and the other walls a light green.

All was well, but a month or so later random patches of the feature wall, dark green, started to show darker patches like they were damp.
I thought they may sort themselves out over the hot summer but not so.

I have tried playing a gentle heat from a fan heater on them and they do begin to fade, but as the surface cools down they reappear.

One possible reason for the "damp" patches maybe that I blended in the new plaster to the old plaster with a very thin layer, max 1mm, of normal filler and filled in slight dips.
This may be why the patches are so random over the wall.

I think the only solution, and yes, I should have done in the first place, is to rub down the patches to get rid of the filler and apply a breathable filler.
Which brings me to my question, what breathable filler would you recommend?

Thanks in advance.

I'm not exactly sure why you were using this filler at all, the lime plaster would have filled the hollows in the wall surely?

Was this a skim? LG Solo can be applied in 2 passes, one straight after the other, to achieve considerable thickness if required.

Perhaps I'm misunderstanding something.

 

[Dazed&Confused]

I'm no expert by any means, but your predicament interests me for selfish reasons. I would suspect that rather than attracting damp, the filler is just holding onto the natural moisture in the air, whereas the lime plaster is letting it escape.

 

[Lacan07]

I'm not entirely sure what could be causing the patches other than historic salts, the filler sounds unlikely to me.

Did you notice any patches previously? Are you sure the patches are where the filler was applied?

Perhaps some photos would help.

 

[Cubist]

Hi Keith,

That leaves me shrugging my shoulders and muttering 'no idea pal'. Lacan and D&C seem to have a better handle on this one.

Cheers, Cubist

 

[noj]

I guess you could just go for a lining paper and paint that?

Relatively quick, not expensive and mess free.

It may not solve your problem, but then trying to replace the filler and get an acceptable finish may be a nasty job with equally no guarantee of success...

 

[keithevans595]

In answer to Lacan07 answer, I'm 95% certain the patches are where the filler was applied.
I'm also uncertain why I was using this filler also!!
The point where I used the filler was the joint between the new lime plaster and the old plaster and there was a small step which was too much to ignore.
I also thought the Solo plaster was too course to get a good finish.

I don't think it will be to much effort to remove a millimetre of filler and get back to the new plaster and re-do it with a smooth breathable filler and re-paint over.
I didn't notice any patches previously but the dark paint colour seems to show up more imperfections than the lighter colour.

 

[Lacan07]

In answer to Lacan07 answer, I'm 95% certain the patches are where the filler was applied.
I'm also uncertain why I was using this filler also!!
The point where I used the filler was the joint between the new lime plaster and the old plaster and there was a small step which was too much to ignore.
I also thought the Solo plaster was too course to get a good finish.

I don't think it will be to much effort to remove a millimetre of filler and get back to the new plaster and re-do it with a smooth breathable filler and re-paint over.
I didn't notice any patches previously but the dark paint colour seems to show up more imperfections than the lighter colour.

Well it must be the filler thats causing the issues then, what rotten luck! I wonder if the clay paint has reacted differently to the gypsum background?

The point I was trying to make was I don't know why you were going in after the final skim to make repairs // fill joints, etc. I would have thought it should have been addressed when the wall was being plastered.

If you wanted to scrap away the filler and start again I'd use the same lime plaster you used for the final skim to make the repairs. Obviously I don't know what you used but if it were Solo, for example, I'd apply the plaster, wait a while for it to harden, then float (smooth over) with a damp sponge and shortly after that flatten with a flex trowel. The same process would apply to lime putty finishing plaster.