Spot that building material

Hi all,

Anybody know what this building material is? For context you’re looking at a little hole in the plasterboard revealing the polystyrene insulation and the unknown construction material behind. It’s in the extension part of a house.

Thanks in advance!

It looks it might be this:

That’s interesting, thanks Nigel. However that seems to be some sort of plasterboard (I get gypsum plasterboard as an English translation) which suggests it’s not the main material of construction? Could it be glued directly onto, say, concrete blocks? It feels very solid when I tap it

From that picture …it looks like the back of plasterboard given colour and uniformity. But what’s on the other side and how thick is the wall. What does it feel like …
To be honest just cut a section out and see - or just poke it with a screwdriver and see if it’s obvious.

Just looks like a small hole in a polystyrene plasterboard. Yes you can dot and dab it to walls with PM1 adhesive or use low expansion foam in a can which is what I use.

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what’s underneath… looks like old cream paint, thickly applied on an old plastered wall. Most of our house looked like that, slightly glossy… and quite hardwearing.


Thanks all. Just to reiterate that the photo in my first post shows a whole in the outer (ie, room-side) plasterboard which reveals the polystyrene insulation and the mystery material behind, which when tapped/knocked feels very solid (ie. it’s not possible to cut a section out).

In this pic you can see where the interior plasterboard and insulation ends by the door (the door is open - the outside of the building is on right, the inside on the left). The end of the knife is touching the mystery material which is uniform all the way down. It’s flush with the exterior wall (white on the left).

That looks like PM1 they used to bond it to the wall?

It looks to me like an epoxy resin product, similar to what I just used about an hour ago to fix bolts into concrete steps, to fix a steel handrail securely in place. Exactly the same colour as well.

Thanks hairbear - could it be that a whole extension was constructed of epoxy resin though? Seems unlikely from what I can find online

what is the other side of the wall?? is it your property or next door???

The other side of the wall is next door (also an extension)

maybe ask them what the wall is made of… ??? perhaps get the plans from the Mairie…

Must say I’m rather with Stella on the idea that it may be a block/cement wall thickly covered in cream paint… is that possible?

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Yes I guess it could be that. And then someone came along later and added insulation and a layer of plasterboard to insulate it?

how old is the property and how old the extension??

makes sense to have some insulation between properties… sound/heat-loss etc etc… just thinking aloud…

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It looks like a plastered wall that has been painted probably more than once over the years. We had walls like this and they were constructed with red briques.

Stella’s right - it’s the original wall. Someones dabbed)dotted plasterboard directly to it.

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Looks like some kind of polyurethane spray coating.

And very common to prevent draughts to try and achieve a continuous line at the edge of a run of boards.
What makes you think tc123 its not PM1 board adhesive?