What type of mortar is under the plastic paint I have sanded down?

[Daniel Johnsson]

Hello!

I've sanded down plastic paint from the inside of a brick wall and am trying to figure out what type of plaster/mortar is behind it. Is it gypsum plaster? It feels very "fine" in the hands.

The house is from 1850 but has been renovated in stages later on, and since one wall has been damaged by the plastic paint used, I want to use something vapor-permeable instead (how does gypsum plaster work in this context?).

Since I need to even out the wall after sanding, I'm pondering what's behind it. If anyone with a keen eye has any tips, I'd appreciate it.

There are also some individual holes, and the mortar behind the finer layer is quite porous. We had an inspector on site who measured, and other walls (including this one) are supposed to be "dry."

Best regards, Daniel

 

[cpalm]

What we see is probably some kind of spackel.

 

[Daniel Johnsson]

What we see is probably some sort of filler.

Thanks for the answer! I wouldn't be surprised, but is it common to use?

By the way, is it appropriate to apply plaster on this, because I assume lime mortar won't adhere?

 

[cpalm]

Thanks for the answer! It wouldn't have surprised me, but is it common to use?

If it's common to putty the whole surface before painting? Yes. But I assume that's not what you mean?
It appears there are a number of paint (and potentially putty) layers there on top of the plaster.

What is your end goal?

 

[Daniel Johnsson]

If it is common to skim coat before painting? Yes. But I assume that's not what you mean?
It looks like there are a number of paint (and potentially skim coat) layers there on top of the plaster.

What is your end goal?

Of course, I understand that it's common to skim coat before painting, I meant whether it's common to choose skim coat over some kind of plaster.

In any case, I've sanded down three layers of paint, so what you see is some form of finer plaster or skim coat as you mentioned, and a more porous coarse mortar behind it.

What I want to achieve is to remove all the plastic paint from the exterior walls. I have milled it down with carbide discs to "only" take off the paint; I want to avoid sanding/chipping off all the existing plaster due to the work involved (as there are quite a lot of wall areas in the house). So now I'm unsure which mortar I should choose. I want to smooth plaster everything anew and create a diffusion-open wall. The plastic paint has caused problems on one of the walls, as mentioned.

 

[cpalm]

Of course, I understand that it's common to fill before painting, I meant whether it was common to choose filler over plaster of some sort.

No, you simply haven't gotten down to the plaster yet, and are still working on the paint/filler layers that lie on top.

If you are going to smooth plaster with plastering mortar, you need to work your way down to the plaster; preferably, it should be completely free of even small paint residues for a good result. It's not a fun job, sometimes it can work better with a shearing scraper, like Olfa.

 

[Daniel Johnsson]

Is it that bad, then just go for it again. Will try with the scraper as well, have used it in some places. But it's definitely a tedious job.

Which plaster did you use? A finer lime plaster or gypsum plaster?

 

[cpalm]

Which plaster would you have used? A finer lime plaster or gypsum plaster?

1 mm lime plaster

 

[Daniel Johnsson]

1 mm kalkputs

Thank you for the answer. Have a nice evening!