Ancient layers - Lime, cement, filler and - How to prep for plaster?

[Stubbsk]

We stripped the lining paper because it was beyond salvageable and we have some nasty surprises underneath.

So the entire house appears to have been plastered/rendered with a cement product (see the grey on the left) and although most the walls are fine, it has failed on the chimney breast and front wall, revealing lime plaster underneath (including animal hair), which would have been the finish to the old bungaroosh walls. The joys of a Georgian paupers house.

So, what do I do about cement (if it is cement)? I have holes to fill, and can I use a smoothing product on it where the walls are sound, if not how do I prep it for a skim coat? And is gypsum multi-finish ok?

And the lime, how do I prep that? I can't plaster it in lime as it's just a few square feet of the entire house, everywhere else the grey/cement has adhered fine. Is there some undercoat or bonding substance I can use? Then do I go on to gypsum?

And also, I'm sure there is still lots of wallpaper paste on the walls too, so any tips on that will help, just carry on steaming and scraping right?

I'm thinking of a DIY approach, either the entire thing, or if I'm awful at it, perhaps just get the walls prepped for a pro to skim.

Your advise is really welcome, even if I don't touch it, as I feel too clueless to trust myself to agree on anything with a plasterer just yet.

 

[Deleted member 292770]

cement and gypsum is not an option.
lime , lime and more lime. good luck.

 

[Stubbsk]

cement and gypsum is not an option.
lime , lime and more lime. good luck.

But the house is already plastered in cement...so it is an option...

 

[RandomGrinch]

Hi,

I'm only a DIY'er, so I may be wrong (...and hopefully not too wrong to feel the wrath of Godwas! )- feel free to ignore!

The problem is, cement/gypsum products and lime are usually seen as incompatible technologies!

Lime is breathable, whereas gypsum is hygroscopic. If you skim with gypsum over the top of lime (as in my Victorian terrace), the plaster can blow, destroying the underlying lime in the process.

In your case, the damage may already have been done.
You could be ok; it's possible the render could be forming a hard shell in itself, that holds everything together.
However, this won't preclude the possibility of hidden issues behind the render and damp problems.

If you re-skim with gypsum, it may fail sooner, or later.
The alternative though, would be some major work to strip everything back.

Sorry if that doesn't sound very helpful

Good luck!

 

[Stubbsk]

Thanks RandomGrinch, but I understand this, hence the questions!

If I thought they were all compatible I would have dived straight in blissfully ignorant.

You've hit the nail in the head though, 'the damage has already been done', we can't realistically take it all back to the lime and refinish, I need the best advice to make do with what we've got.

I'm non the wiser though, is there a better approach then PVA and Multifinish...

Perhaps I should reframe the question and try again.

 

[RandomGrinch]

This is where your judgement and compromise comes in!

If you haven't got the budget/time to strip everything and start again, what can you do?

Again, I'm not an expert!
Perhaps, use multifinish on the hard cement areas if they are sound, on the understanding they could fail?
May be use something like Limelite on the failed areas?

Factors such as, is this a forever home, may change the balance of the equation!

One thing to take away - and I have also learnt to my peril - don't remove any more wallpaper!