Crumbling Plaster

20 Sep 2016
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United Kingdom
Hi, I am new to the forum.
I have very little DIY Experience but I have just inherited a 1920's semi detached so trying to fix it up.

This room once had damp/mould I think due to lack of ventilation.
I have kept it ventilated for a while now but when I came to strip the wallpaper. The plaster is loose and crumbling.
They are both upstairs exterior walls in the corners. I have removed most of the loose plaster.
My questions are.
1. How do I know if the damp has fully gone.
2. What's my best course of action on the plaster.

Pictures attached.


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Hi and welcome, Wardy!
Always expect old plaster like this to come off in abundance......that's just what happens!
As for the damp situation, obviously we can't tell from here, although it would seem to be fine.
What's the condition of the roof, guttering, and so on above the suspicious area?
John :)
Thank you for the reply.
I did have a look at the brickwork and tiles and my although inexpert eye didn't see anything wrong. I think the Guttering has recently been cleared out too.
So will it be ok the progress onto replastering?
Is it best to do it in patches or re do the whole wall?
Is it a easy job or is it best to get an expert in??
Last edited:
For sure, speaking as the worst plasterer in the entire world I'd get a pro spreader in.
Ask one to call and maybe you can do the prep work like hacking the old stuff off - again, he should be able to advise but it sounds like the whole wall will need doing.
Any current damp should be evident.
Good luck with your project!
John :)
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The walls I think will be lath and plaster. I would get all the old plaster off down to the laths| It will be very dusty and a lot of mess so wear a good quality mask and try to not break or pull the laths off .After you have done that see what the laths are like and if they are wet and loose rip them all off so you are left with just the stud work. You will have to take the skirting off aswell .The studs will probably be either 14" or 16" apart and will need all the old nails taken out. Usually you can drag the claw end of an hammer down the studs and the nails should break off, the ones that dont just pull them out. Then you have a blank canvas to reboard and skim. (This is where you bring a few plasterers in to give you a quote, also while the wall is all stripped off you can check if there is any rot or damp in the stud work, I think the window wall and around the window might be letting water/damp into that corner and tracking back onto the stud wall. I have had the same problem in my old Victorian house and have addressed the problem. If you look in my albums you will see what I did in my bedrooms.If you think it might be too much for you then you can get a few builders/ plasterers around and see what they say and how much they will charge. Then come back on here and let us know what they propose to do and how much...Hope this helps a bit....
"that's just what happens!" - no it isn't, what nonsense to say such a thing.
And "the damp situation ... would seem to be fine." more rubbish, pretending to be knowledgeable advice.

The background plaster is crumbling - possibly due to excessive moisture.
You have indications of condensation (or perhaps damp penetration) where the ceiling meets the wall(s).
On the lower wall(s) you have skim finish over polystyrene.
In pic ...175 - If the crack in the upper corner is opened up and followed it might reveal a crack running down the inside corner of the walls.

OP, Go into the loft & investigate above the area in question. Look for damp.
External view photos of the two walls would help.
On the gable wall you might be best hacking off all plaster back to bare brick & then posting photos of any cracks.
Without seeing a photo of the window wall its hard to say what you should do.

Is the ceiling firm, smooth & crack free?

OP, Its not enough to just look up from below - someone has to go up to the roof & photo whats existing on the roof, chimney stack(s) and eaves, fascia & guttering.
Thanks Roy c. How long can I leave the laths exposed for? Not sure when I'd be able to get a plasterer in. But also wouldn't mind getting on with the job.
Good post Roy.....on the occasions I've been faced with this, I've removed the old laths and boarded over.
Thankfully the mess didn't matter.
I then made contact with the spreader - I've so much respect for those guys.
John :)
Thanks for the reply vinn. The loft is converted into a bedroom. Some years ago and has been plastered. There is a lot of mould but no damage to plaster up there. I presumed this was due to ventilation again as the window and been shut for a few years. The ceiling in the bedroom is solid with no cracks.

What specifically should I look for on the exterior that could cause damp?
Doesn't look like polystyrene to me , looks like previous repairs a 20s house wouldn't have originally been plastered with gypsum plaster.
But I disagree, plaster that old does fail without there being damp involved but if they are exterior walls then they won't be lath and plaster and can be very susceptible to failing due to damp. Look outside for signs of water staining to the walls , leaking gutters etc and see if the walls are actually damp.
Either way it looks as if its time to strip that lot back to brick and start again, you will then know for sure whether there are any damp issues
I have come to realise that what I posted last night was completely different from what you have.I automatically thought of what I had done to my own property and I had it in my head that you had the same scenario but you havent,:( But what the lads have said is more appropriate to your problem, but you will know what to do if you come across any lath and plaster walls!!
Sorry I forgot to mention! Seems a lot going on in this room and I've slept since then. But on the other side of window the plaster was crumbling even worse than the pictures. I broke off all the plaster and it is wooden laths behind the plaster.

I need to get hold of some ladders to inspect the roof and walls for pictures. I'm also getting a friend who's a plasterer to give his opinion. Will keep u all posted.
OP, would you post a photo of this new exposure of "wooden laths behind the plaster"?
Vinn unfortunately and somewhat embarrassingly I tried replastering it myself with some b&q ready mixed plaster( this was a while a go!) But the laths seemed dry and in good condition. Would it help if I removed the plaster that's loose to show u the condition there before I get some propper ladders!!
Haha blushing here!

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