Patching old gypsum plaster after removing wallpaper

[lizziecupcakes]

Hi all, I have a 1907 Edwardian house.

Sadly, due to budget constraints I cannot apply lime plaster (yet) so it will be about 5 years or so until I do that (I literally calculated what I could save up!). I hope to do this during a bit of a “back to brick” project and also install wood fibre boards.

The situation now: Our main bedroom is having a new plastered ceiling with plasterboard and usual gypsum skim. I’m all good with this and will go ahead with this plan.

This post is about the said bedroom walls though. The wallpaper is terrible and very dated (1970s) so naturally we want to update the room and also use it. We are currently in a different bedroom to sleep in.

I’ve stripped back some of the wallpaper to the see the condition of the gypsum plaster underneath. I’ve knocked on it with my knuckles and it doesn’t sound hollow. I don’t think it’s blown at all.

However, while stripping the wallpaper, it pulled off a bit of the plaster with it (quite superficial though) so there are small patches of this on the walls. I’ve attached photos if that’s helpful (some show the whole wall and then closer up of how far apart the patches are, another shows close-up of the patch to help you see it more closely).

Where there arent patches, the plaster feels very stable, not crumbly at all and pretty good condition in my inexperienced opinion.

I was originally going to get a plasterer to skim the walls and then I’d paint on it (I only want to use paint). My mum came round yesterday and she told me that last year in her 1990s house, she stripped her wallpaper back to plaster and she also had the same random small patches pull away with the wallpaper coming off. She advised not to bother with the skim plastering and to save the money instead for the future lime plastering work. She said she patched her bits up the following way: she sanded the patches down then used something like polyfila to fill them, then sanded it down again to smooth, then she put new wallpaper again (not paint). She likes to put up wallpaper and paints on that (I don’t know why), but she thinks it’s easier to do that. She also thinks I should sand down the entire walls a bit too.

Love my mum, but we are both inexperienced and we have two different houses. But now, i think maybe the condition of my plaster is not too bad? Or is it? As mentioned, it’s not blown which I’m confident about, but I don’t know if my mum’s patching up the loose bits will be good enough to make the plaster okay for paint and leave a decent finish. I’m not too bothered about perfectly smooth walls, but something decent has to work.

The other question I have is, how do I then prepare this old gypsum plaster for paint that had wallpaper on it since the 1970s?

Thanks all!

 

[lizziecupcakes]

Above, I also circled how far apart the patches seem to be.

 

[fernicarry]

then she put new wallpaper again (not paint). She likes to put up wallpaper and paints on that (I don’t know why),

Probably lining paper. Preferable to painting directly onto the plaster. You will still need to get the worst of the defects out of the plaster by filling and sanding but a mid to heavy gauge paper will hide quite a lot. As with all decorating its 90% prep.

Its just about the least expensive material you will use so if you mess up just peel it off and try again. For small mistakes a thin skim of filler and a light sand before painting and no one will ever know.

Is the white stuff definitely gypsum? The pink repairs around the electrical sockets will be (and they look rough as a badger's...).

 

[lizziecupcakes]

Haha. Yes around the sockets is bonding plaster (appears pink) the electricians used and applied (i had a rewire). I’ll be applying a layer of polyfila or similar on top of it.

The rest of the plaster I believe is gypsum. It’s hard as nails and i did the vinegar test and there was no fizz. I believe it’s been there since the 1970s, but who knows really. It’s definitely not lime.

I’ll look into line paper, thanks for the suggestion. I really prefer to paint it directly onto the plaster though.

I’m glad it sounds like I can just patch up these bits of plaster that have flaked off with the wallpaper removal. I look forward to getting lime on the walls in the future!

So, you don’t think i need a mist coat before painting directly onto the walls after the repair?

 

[Stevers]

That is well within the scope of the gentle art of 'decorating' rather than 'plastering'.
Looks like the original lime plaster to me, and about as good as it gets prior to a bit of patching. Thistle One Coat is available in sensible size bags from the likes of Wickes and is one option for the bigger patches. It is gypsum, but I have found it remarkably tolerant of old building nastiness. In a plastic tub it will stay fresh forever.

 

[lizziecupcakes]

Thanks @Stevers !
Which bits do you think is original lime plaster?

 

[Stevers]

All but the pink! The rest looks just like all the original lime plaster I've ever seen on houses of that sort of age.

But whatever it is, why replace if it's as good as that?

 

[lizziecupcakes]

Thanks again @Stevers . I did a vinegar test where i had some vinegar and took some of the crumbled bits to see if it fizzes. Lime would fizz, but this didn’t so I think it’s all gypsum

Thanks for saying based on the photos you think it looks in good condition. I’ve never done this before so everything is a stop and check process eek

 

[Cubist]

Most of the damage seems to be separation of the skim coat from the base/render plaster. There are several possible causes but some of those shown appear to be associated with where rawlplugs may have been inserted at some stage. Once repaired though I would be nervous of painting directly onto the plaster as this could risk more of the skim coat becoming detached. You might want to consider either using a lining paper as suggested above or perhaps using a suitable stabiliser to strengthen the plaster first.

 

[Cherryburn]

I think the "fizz test" can sometimes be misleading if people are expecting a big reaction like you'd see in a chemistry classroom. In reality it's just a few small bubbles after several minutes. Regardless, you can definitely do a lot with just filler once you get the hang of it. Need to slightly overfill then sand back once it's dried. Good rule to remember is that any imperfection you can feel with your fingertips would show up on a final painted surface. Less so if you're using lining paper, but that should give you an idea of whether you'll need to or not.

 

[Stevers]

I did a vinegar test where i had some vinegar

Loss of servicable original fabric, and a lot of expense resting on a fizz test!

 

[lizziecupcakes]

I think the "fizz test" can sometimes be misleading if people are expecting a big reaction like you'd see in a chemistry classroom. In reality it's just a few small bubbles after several minutes. Regardless, you can definitely do a lot with just filler once you get the hang of it. Need to slightly overfill then sand back once it's dried. Good rule to remember is that any imperfection you can feel with your fingertips would show up on a final painted surface. Less so if you're using lining paper, but that should give you an idea of whether you'll need to or not.

I did not know this!!! Thanks for sharing, and very true @Stevers .

Can I ask what features of it makes you think it’s lime? This is really intriguing me!

 

[lizziecupcakes]

@Lacan07

i know you applied lime to your own walls yourself, so would love to know your thoughts too! Do you think the walls are lime? (Expect around the sockets, that’s defo gypsum)

 

[Kearn]

That’s not gypsum. You have a lovely lime wall there, with some very small easy fixes . Please don’t remove any more original lime plaster and replace with modern materials.

While it may sound like heresy, for small patches in lime, polyfilla can work well. It won’t impact the performance of the entire wall. Much easier, and cheaper than trying to patch in a top coat of lime and allow for cutting back angular edges in the existing, knowing where to stop and over filing to allow for shrinkage etc

 

[Lacan07]

@Lacan07

i know you applied lime to your own walls yourself, so would love to know your thoughts too! Do you think the walls are lime? (Expect around the sockets, that’s defo gypsum)

Yes, that's probably the original lime plaster. Quite a lot of people compromise on the upper floors and choose to gypsum skim the walls, with the exception of the external facing walls. But if you're intent on lime plastering / skimming this bedroom I would simply concentrate on prepping the walls - remove the wall paper, repair the small patches with Polyfilla or Easifil, (or there are lime based equivalents made with chalk dust), give it a good wipe down, and then just wait until funds are available. Its perfectly liveable imho, I've been living in far worse. To be honest I'm not sure I'd even bother with the patches, let the plasterer deal with it when the time comes.

 

[fernicarry]

I use the same skim for repairs as is used for taper edge plasterboard. Repairing the polish coat is about the right thickness for it and its really fine so sands nicely. It doesn't do well on deeper fills though tending to shrink or slump. Be careful sanding back into the existing plaster as the polish coat could be very friable and you end up with increasingly large repairs...

For making good around your electrical outlets, these are really good. Especially if you have my level of OCD and can't abide paint or plaster inside the back-box....

 

[lizziecupcakes]

Thanks @fernicarry - I’ll have a look at those in the link you sent. When I add polyfilla, do I have to detach the sockets from the wall? i might need to add a bit more bonding plaster around the edge too.

Thanks @Lacan07 for your advice. I think to preserve the current wall for as long as possible i’m going to use lining paper and paint on that, rather than directly paint on it. Knowing me, I’ll want to change the colour in a couple of years, so I think this will give me more flexibility.

I did find an area of blown plaster though in the corner and seems to be down to a leaky gutter on the external wall. It’s about 50cm x 1cm which is relatively small in the grand scheme of things. Roofer says he can’t see any problems with the roof in this area, including parapet wall looks a bit cracked but no major concerns and he will repoint it, and felt in the area looks good too… although the lead flashing needs replacing due to a lot of cracking. It looks like there has been a very slow moisture problem or damp problem here making the plaster go all powdery. I’ve already planned to have new gutters and lead flashing throughout in the next few weeks and repointing the Parapet wall.

My question is: I intend to cut out that section of powdery plaster and take it back to brick to dry out. Should I use a lime based plaster in this section or does anyone have any suggestions about what I should do with this?

Photos attached too - where you see the boggy parts in the wallpaper, it’s completely dry but when I cut into it using a Stanley knife, lots of power plaster comes spilling out. When I tap with my knuckles , this section is hollow. But to the touch, it all feels completely dry.

Thank you all

 

[fernicarry]

do I have to detach the sockets from the wall

For best results, yes.

You want to make good up to the edge of the back box thats buried in the wall and then the electrical outlet's faceplate will overlap by a few mill all around once reattached to give a nice sharp join. Same with the lining paper so that the cut edge of the paper ends up tucked under the faceplate Nothing worse than paper cut around the external edge of the outlet, but sadly all too common.

This yellow collars do rely on there being a bit of give in the cables though and yours are plastered over so that may not be the case. Best check before ordering. Given how shonky that multi-finish is I don't think you'd got much to lose by digging it out and putting the cables into conduit before making good again but that's my OCD talking again. I always ensure a bit more cable can be drawn into the back box for future changes of mind without having to disturb the decorative finishes.

 

[Apasc]

I’ll look into line paper, thanks for the suggestion. I really prefer to paint it directly onto the plaster though.

I’ve not tried yet but have been advised that Wallrock fibreliner is the way to go. Good luck and please let us know how it is going.