Exterior lime render

[PinkCamelias]

How can I tell if my house is externally plastered (rendered?) with lime? I'm wondering about that, because I'm thinking about externally insulating the back and I would like to know this before I speak to the builder. The house is from 1908, and not in the UK, if that matters?

The back is painted white and the plaster is not chipping, so I could not find a bigger sample. What I see is that it's certainly sandy. I took photos of a small hole above the window sill, and a line where the house wall finishes and red brick garden wall starts (I dug out some pointing from the brick wall and it crumbled easily).

Thanks for any advice!

From the age it’s likely to be lime.

But if you’re getting a builder in to insulate the outside, they should know how to approach- if they don’t they’re probably not a very experienced builder.

The test for lime is to chip a piece off and put into white vinegar- if it starts to bubble and react fairly quickly, it’s lime.

Thank you, @Lonelycrab , I will test it with vinegar!

I don't know what the builder's experience is regarding lime plasters, he certainly has experience with insulation. I would like to know what to tell him when I ask about this job, to be clear what I'm expecting. He's used to modern building materials, so that's his default.

You sound like you have done some research already but in case you haven't, be careful insulating old houses as it can cause issues with damp if the breathability of the building isn't taken into account.

That’s exactly what I have in mind, @Geneticsbunny . I want to do my research so when I speak to the builder I can see if he is on the same page! I think we need to insulate because the back rooms, including the bathroom, are quite cold. Roof insulation was not enough, and one room has new windows, so there is nothing else left. House is very dry, no damp at all, and I am aware how important it is to be careful with that.

I would be interested to hear what insulation you go with in the end. We have a similar issue.

Join the group Repair and Conservation on FB for advice from those in the know:
www.facebook.com/share/g/1DHACy5Z5Y/?mibextid=K35XfP

I will let you know, @Geneticsbunny ! However, it is not going to be soon - next year hopefully, depending on the builder's availability, and the quote :) (we have to save!). But I will speak to him to ask about the quote, and this will also mean discussing the technique.

Its hard to tell from the photo but as others have said, as its 1908 construction it is likely to be lime. It looks like thats plastic paint which will need to come off which may cause some damage. I'd look at using a doff machine for removal. Where are you based?