Do I need to use a lime plaster?

[Daj117]

I have a semi detached 2.5 bedroom house built in the 1890's. The walls are of cavity construction and I believe bricks have been laid with lime mortar. Having removed the wood panelling covering the bottom half of the walls in the smallest first floor bedroom I found the lime plaster underneath falling off the walls so I have removed that and the plaster from the top half of the wall that looks like it was skimmed with gypsum plaster at some point in the past.
My question is... do I need to replace the lime plaster with a lime product?
Thanks for your help.

 

[Ambergreen45]

It's all to do with damp, mould and mildew. There are rules for graded listed properties, but it's unlikely yours fall into that category. Lime plaster and it's associated products such as breathable paints can be expensive. Traditional lime plastering is done slightly differently than Hardwall and Multifinish. In my case I re-plastered my fireplace with lime plaster because it's heat resistant and breathable, gypsum is not. But if you have a damp course, the work is to be done inside the building and the bedroom being on the first floor, if there are no damp issues, even though it's best to replace like for like, I personally think you might be ok using gypsum plaster.

 

[vinn]

It might be best for you to hack off all the plaster on the affected walls - from floor to ceiling.
Come back here If you have a picture rail or coving or expose any unusual growths under the old render.
Remove any skirting as well.
Then render the walls with a 3:1 sand & lime mix and Limelite finish.

Bagged lime is not expensive.

Dont ever use gypsum plaster where there is or was a damp problem.

What condition are the walls in on the outside - are they rendered?
Is there a chimney breast in the bedroom?

 

[Daj117]

Thanks Ambergreen.

Vinn, all the walls have been taken back to brick. I see no evidence of any damp. The old lime plaster (along with a few layers of wallpaper and ghe original skirtingboard) had been covered up by panelling halfway up the wall.

As for a chimney breast I discovered the remains of one that must have been taken out over 25 years ago by a previous owner. This was the most difficult plaster to remove as it turns out it was sand and cement.

There is no rendering on the outside of the walls

 

[Ambergreen45]

I thought I might give you a bit more info which you may find useful before you make a decision.

The plaster on my walls is made up of sand/cement. Most plasterers, I believe go for gypsum Hardwall on brick/stone as a base coat and then Multifinish as a final coat. It dries very quickly but the plaster would need to be fully dry possibly for a few months if applying lining paper and an acrylic paint. If no damp problems, cheaper option.

If you fancy going the traditional route, you may have to buy the products online. Usually Builder's Merchants only seem to sell Hydrated Lime which is normally used to mix with sand and cement to make it more workable I believe. I don't know much about Limelite. Online suppliers can give you some good advice and some are cheaper than others.

Maybe an easier way to apply the plaster would be to mix Natural Hydraulic Lime (NHL) with Plastering Sand as a Scratch coat and then as a Base coat. A 25 kg bag of NHL with a strength rated at 2 or 3.5 should cost you about a tenner each, to be be mixed with 2 to 3 parts of plastering sand. It would be like applying a sand/cement internal render, but lime is not as rock hard and would be breathable. NHL can be white or light grey. Non Hydraulic matured lime plaster is the real traditional stuff dating back as far as the Romans, but can be a bit more tricky to work with, though it is a little more soft and breathable then NHL, but takes a lot longer to dry. That's how I plastered most of my lounge and fireplace, with NHL and then applied non hydraulic matured ready mixed Finishing Lime Plaster. Once fully dry, natural breathable paint.

If a plastering amateur you will need a bit of practice, unless you have done it before.

Hope that helps.