Lime plastering

[Sweetpea1989]

Half the house is built circa 1700’s with a 1980’s extension.

In the old bit we’ve had a couple of plasterers quote, one said gypsum would be fine, the other said it needs to be lime.

The gypsum quote is about £300/£400 whereas lime is £850.

It’s just a re skim and it’s a standard double bedroom.

Does the higher quote seem fair? I don’t mind paying if it’s what the building needs but it’s also part of a larger project so there is a budget.

My plasterer charged £300/day plus materials and would easily get a room skimmed in a day. Not sure if it being so old makes a difference though?

Can you get another lime quote? I'd always go for lime as it allowes the walls to breathe.

It absolutely needs to be lime! Please for the love of God don't put gypsum or cement near a period property.

Link to reasons why below.
www.heritage-house.org/damp-and-condensation/managing-damp-in-old-buildings.html

What is there already?
We originally went down the heritage house, everything must be original materials, I will only wear hessian and drink mead etc etc before having some very good advice from an architect friend - you don't live in a museum.
Do you have any damp issues in or around that room now? Is there any reason to suggest you might do? What is currently there in terms of interior decorative materials?
I would be wary of switching from lime to modern unbreathable plaster. But if you already have modern materials and no issues then I'd say crack on.
Note that you will need to buy chalk based breathable paints if you go down the lime route.

I second what Cavagirl said. What are you skimming over?

If there is already gypsum on the walls, or they are sealed in some way, lime is pointless. It won’t magically turn a wall which is not breathable breathable.

Otoh if what there is is lime, you’d be mad to put modern plaster over it.

(to make things really complicated, sometimes a mix of lime and gypsum can be used, but it has to be specific types of both)

If you're redoing exterior walls, you're asking for trouble putting gypsum and plastic based paints on them. I'd use this as an opportunity to get rid of it if it's there at moment.

If you're redoing interior walls, may not be as much of an issue but would definitely steer clear of using gypsum and plastic based paints on chimney breasts as salts from soot can react with them.

the one who said Gypsum may not have liked, or been competent with, lime.

When I had some done the builders brought in a local specialist.

Lime costs a lot more per bag !