Is this blown lime plaster?

[lizziecupcakes]

Hi all, I am in the middle of figuring out what to do with my main bedroom in my Edwardian 1906 house. The previous owners lived here for about 40 years and didn't do much with it (this century). The main bedroom is wallpapered (probably from the 1970s). On a few corners of the room, the wallpaper has come away from the wall a little (there is no obvious damp or anything; t's just old wallpaper coming off a bit). So, I've pulled it off a bit more, but then some plaster (??) came off with it.

I scratched the plaster with my nail and it's quite crumbly and chalky. There's also some weird dark-grey material behind the plaster (i don't know what this is). It's not mould - it looks like some material the plaster is sitting on.

I've attached some pics. One of them shows some of the crumbly bits that fell onto the floor and the dark grey stuff. Does anyone know what any of this is?
Is it just blown lime plaster?

I imagine the plaster is like this on every wall and I have no idea what to do from here.

Thank you

 

[DampedOut]

Ooooh very interesting! Watching this thread.

How do you feel about doing damage or exploring a bit? I'm afraid I'm a bull in a china shop, but not everyone wants to tear walls open to find out what's going on underneath. What's your tolerance level for digging into it?

 

[lizziecupcakes]

in all honesty, i'm probably going to replaster the whole house with lime putty, and use wood fibre boards for insulation
After a bit of googling, I think this plaster is cement + sand mix

I guess my question really is: has this plaster gone all crumbly and getting pulled off with the wallpaper because of damp/moisture?
I'm worried there's another problem beneath all of it.

 

[aockenden]

Judging by the colour of the main plaster (flecked white) I would guess that’s lime, especially if you are scratching it off with a fingernail and it looks chalky. If I try to scratch off the Portland cement render on our walls it would be liable to rip my fingernail off as it’s so hard, and it’s all iron grey anyways which doesn’t fit what you’re showing here.

What those dark grey / black sections would be, I’m not sure. It certainly appears darker than your typical Portland cement render.

 

[DampedOut]

If you're willing to dig into it, you could take a standard claw hammer, and try to pry some off with the claw (assuming you don't have specialist tools yet). Then drop a chunk into vinegar.

If it doesn't fizz, it's straight up cement. If it fizzes slowly or like an ice cube in soda, you may be looking at a mix of cement with some lime or more likely stone dust in it. If it fizzes like alka seltzer, then it's lime.

Why it's gone crumbly, I'm sorry, I wish I knew. I think once it's super clear what the material is – or what the layers of material there are – then it'll be easier to figure out what could have happened with the top layer.

Don't want to jinx it, but I'm hoping for lime.

 

[malcolm]

If that is vinyl wallpaper then it will be waterproof. In the summer water will be drawn towards the colder interior and make the surface of the lime wet, which after a while that makes the surface a bit crumbly.

If that is the case then you should be good just filling in the cracks, adding lining paper using a cold water starch paste, then painting in something breathable. It's a bad idea to paint directly onto the lime as at some point someone will use a modern emulsion paint which will be impossible to remove without removing the lime.

 

[lizziecupcakes]

Oohhh the vinegar test! I'll do this and update you all with results. Thanks for this!

I also think it's lime, now that you've reminded me that cement would break my nail! haha

@malcolm that's a very good and reasonable explanation. It could be vinyl wallpaper and it's trapped all the moisture behind it all these years.

I can't wait to strip it back to brick, but also quite nervous about what i'll find. My funds aren't great, so thinking about living with a few things for a bit before tackling them, in order to save up.

I just really love the house. My first