Plaster in a 1850's town house

[curlydog]

Can anyone advise me as to what sort of plaster was on these walls? I had assumed it would be lime based. But the plasterer who came to give me a quote said it wasn’t. He said it was just a bonding coat, and there was little point me asking him to lime plaster it. He said it would be best just to give it a new bonding coat, then dot and dab and put up plaster board! I looked at him in mild shock.
What should I put on these walls please?Under the window there is a tough cement render, obviously added later.

 

[paulc]

Well, I see hair in the thick base layer and some coarse aggregates mixed in. Then a thinner white layer and possibly a very thin top coat.
In all, looks like lime plaster to me. Certainly not a modern bonding plaster.

Methinks this plasterer needs to go away and learn a bit more about identifying lime plasters while someone else who knows about these things does the job properly.

 

[Itchinfilth]

Echo the above comment.

 

[Lacan07]

Can anyone advise me as to what sort of plaster was on these walls? I had assumed it would be lime based. But the plasterer who came to give me a quote said it wasn’t. He said it was just a bonding coat, and there was little point me asking him to lime plaster it. He said it would be best just to give it a new bonding coat, then dot and dab and put up plaster board! I looked at him in mild shock.
What should I put on these walls please?Under the window there is a tough cement render, obviously added later.

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Looks like lime, as long as that top coat is white and not pink? Why are you removing it?

If there is wall paper on top just remove that.

For replacement just do like for like on the external walls, or if you want to insulate employ wood fibre board.

 

[curlydog]

Well, I see hair in the thick base layer and some coarse aggregates mixed in. Then a thinner white layer and possibly a very thin top coat.
In all, looks like lime plaster to me. Certainly not a modern bonding plaster.

Methinks this plasterer needs to go away and learn a bit more about identifying lime plasters while someone else who knows about these things does the job properly.

Thank you. There was horse hair in it as I chipped it off. It’s very pink and coarse, and also quite sandy. I’d ideally like some sound insulation on the party wall, which is only one brick thick and it’s their shower the other side. The external wall is horribly cold throughout the winter, I’ve no idea if there's a way of insulating it in accordance with regs.
I'm getting a second opinion this morning.

 

[curlydog]

Looks like lime, as long as that top coat is white and not pink? Why are you removing it?

If there is wall paper on top just remove that.

For replacement just do like for like on the external walls, or if you want to insulate employ wood fibre board.

There was a leak from the roof above, so the alcove plaster fell away and much of it had popped. My builder said to take it back to brick or something that wasn’t crumbling off. The paper seems to be holding the ceiling up! Which is slightly worrying.
I was trying to do like for like, but was thrown when the chap said it wasn’t lime plaster.
Wood fibre board? ….I'll do some research. Thank you.

 

[Lacan07]

There was a leak from the roof above, so the alcove plaster fell away and much of it had popped. My builder said to take it back to brick or something that wasn’t crumbling off. The paper seems to be holding the ceiling up! Which is slightly worrying.
I was trying to do like for like, but was thrown when the chap said it wasn’t lime plaster.
Wood fibre board? ….I'll do some research. Thank you.

Thats the original lime under that wall paper so keep as much of it as possible

 

[paulc]

Thank you. There was horse hair in it as I chipped it off. It’s very pink and coarse, and also quite sandy. I’d ideally like some sound insulation on the party wall, which is only one brick thick and it’s their shower the other side. The external wall is horribly cold throughout the winter, I’ve no idea if there's a way of insulating it in accordance with regs.
I'm getting a second opinion this morning.

If you have removed more than 25% of the plaster on an external wall, Building Control should be informed. Some take the view that as it doesn't affect the external appearance, BC are never going to know, so just get on with it.... Even if you do go for building regs compliance, there are cop-out clauses that can be invoked. The main one is payback. If the cost of insulating a wall exceeds the savings made on heating in a 15 year period, you only need to do the best you can without making matters worse.
For a solid 9" brick wall, around 140mm of wood fibre board would get you to the required target of 0.30 W/m²K at a cost of about £20 per square metre (plus labour & plastering). If you were to use PUR/PIR (Kingspan or similar), you would only need ~65mm at a cost of £30/m² - Yes, I'm quite surprised at the difference in price, but then something like Steico-Flex would likely incur a delivery charge (£60 to £100 ?) unless you could get it from a local builders merchant.

If you do decide to insulate the external walls, don't forget to do the reveals around the windows. Obviously, 140mm is going to be impossible, but even 25mm will make a noticeable difference in terms of reducing condensation.

 

[curlydog]

If you have removed more than 25% of the plaster on an external wall, Building Control should be informed. Some take the view that as it doesn't affect the external appearance, BC are never going to know, so just get on with it.... Even if you do go for building regs compliance, there are cop-out clauses that can be invoked. The main one is payback. If the cost of insulating a wall exceeds the savings made on heating in a 15 year period, you only need to do the best you can without making matters worse.
For a solid 9" brick wall, around 140mm of wood fibre board would get you to the required target of 0.30 W/m²K at a cost of about £20 per square metre (plus labour & plastering). If you were to use PUR/PIR (Kingspan or similar), you would only need ~65mm at a cost of £30/m² - Yes, I'm quite surprised at the difference in price, but then something like Steico-Flex would likely incur a delivery charge (£60 to £100 ?) unless you could get it from a local builders merchant.

If you do decide to insulate the external walls, don't forget to do the reveals around the windows. Obviously, 140mm is going to be impossible, but even 25mm will make a noticeable difference in terms of reducing condensation.

The second plasterer who just left, is more old school and recognised the lime plaster immediately. He is prepared to do the work with the correct materials - he prefers the pre- mixed type. I now need to do some research into thermal type lime plaster.