Lime plaster skim over original lime plastered walls

[lizziecupcakes]

Hi all
I am about to start a new bedroom (including removing old 70s wallpaper). I know there’s lime plastered wall beneath it as I removed small patches before. There does seem to be paint on it though (not sure the period it is from, so concerns about lead and I will just assume it is lead going forward ).

My question is, Can I skim these walls with lime plaster?

Me and my partner are keen on working with lime plaster for at least one bedroom and thought this would be a good start with it.

In our main bedroom, when we stripped the wallpaper, some of the lime plaster beneath it came off so we just patched it up with polyfilla. Tbh it’s been a pain doing this and although we smoothed it down as well as we could, there is still a bit of bumpiness in those poyfilla areas which are only slightly noticeable at night with a lamp on which casts shadows in those places.

We think skimming this second bedroom will also make the wall smoother and nicer to work with. Perhaps we can also paint on it directly instead of using lining paper?

Overall, the lime plaster wall appears in good condition, but we think patches will appear as we take off the wallpaper (1mm or so thick, not deep holes).

Does anyone have experience with this?. @Lacan07 ? Also, I’m not sure about the painted areas too and if I can skim over that directly.

I would also prefer to use the least time-consuming lime plaster method and product if at all possible.

Thank you in advance

 

[Kearn]

No. A skim won’t work, unless you use nasty non breathable primers to adhere. Rendering the lime pointless.

If you’ve got old lime, leave it be and patch where needed.

Limewash over will help smooth out the gaps, cracks, bumps etc all, as it’s just think coats of plaster effectively.

 

[fernicarry]

there is still a bit of bumpiness in those poyfilla areas

Did you sand the filler? I go over with an orbital with 180 paper and dust extraction. Be careful not to burn through the polish layer in the adjacent original plaster. If you find low spots (put a straight edge over it) then fill again and repeat. Good prep at this point is the key to the overall finish.

Another reason not to skim an existing wall is that you'll half bury the joinery with the extra thickness.

 

[lizziecupcakes]

Did you sand the filler? I go over with an orbital with 180 paper and dust extraction. Be careful not to burn through the polish layer in the adjacent original plaster. If you find low spots (put a straight edge over it) then fill again and repeat. Good prep at this point is the key to the overall finish.

Another reason not to skim an existing wall is that you'll half bury the joinery with the extra thickness.

Thanks @Kearn and @fernicarry - ok, will leave this then. I was really hoping we could but if it’ll add problems, it’s not worth it.

Yes, we used an orbital sander. To be fair, it looks good and pretty smooth, but in lanp low light, you can see some shadows. Maybe we are being perfectionists, I don’t know.

I’ll post pics soon!

 

[lizziecupcakes]

Btw what is the polished layer in original lime plaster?

 

[fernicarry]

Btw what is the polished layer

The top layer of a three coat system. It has a very fine aggregate to give a very smooth finish as opposed to the first two coats that are building up the thickness and getting the wall flat. Here its only a couple of mill thick so its not hard to sand right through it and then you're into coarse crumbly stuff and have to do another pass with the filler.

To be fair an oblique light source will make even the best finish look like the surface of the moon. Holding a work light at a low angle against the wall is a great way to spot areas that still need prep work. The original plaster here has surprisingly large depth variations if you put a long straight edge across the wall. Aim to have your filled areas follow the local curvature and avoid any sudden changes in gradient.