Hello!
We are the new owners of a charming functionalist house built in 1940. The structure is made of brick and the walls are plastered with (what we believe is) lime plaster both inside and out. On the outside, there is lime plaster on the brick, and they have also applied lime plaster from the inside.
Inside, they have put up some kind of paper-covered thin polystyrene (about 5 mm) on the plaster on the walls facing the outside. On the polystyrene, wallpaper has been applied, which seems to have stayed well since the 80s, except for areas where it has come loose where furniture was pressed against the exterior wall.
As the enthusiastic amateurs we are, we have started renovating what will become the little girl's room, opened up the old vent (all vents in the house were sealed from the inside before they applied the polystyrene on the walls), and removed the wallpaper, but we don't know what to do with the polystyrene. Our instinct is to remove it as we can't see its purpose, but someone must have had a reason for installing it.
- Could it have been installed as interior insulation? The house is listed and cannot be insulated from the outside (the polystyrene would then be the only insulation we've found in the walls), but the listing was done in the 2000s, likely long after the polystyrene was installed, so the insulation theory seems unlikely. 5 mm shouldn't really make any difference in terms of insulation, right?
- Could it have been installed to protect the exterior walls against thermal bridges/microclimates when furniture is placed along the wall? We've seen dark spots on the wallpaper where furniture was previously placed tightly against the exterior walls. We've heard from others with similar stone houses that this can happen if furniture is placed directly against the exterior wall.
- Could it be some kind of 80s version of renovation wallpaper applied to enable wallpapering on the exterior walls? On the interior walls in the same room, they have applied the wallpaper directly on the plaster (looks fine and sticks well), but maybe it adheres less well on cold exterior walls, which is why they used the polystyrene?
This polystyrene has been applied to the exterior walls in all rooms except the bathroom, toilet, and a larger room upstairs. In that room, the wallpaper looks as fine as in other rooms. We've Googled and asked construction firms that have been here for other reasons, but no one has seen this solution before.
Can anyone help us shed some light on the polystyrene's purpose? Why is this type of polystyrene used on exterior walls, and most importantly - should we keep it? Replace it with something else? Remove it and wallpaper directly on the underlying plaster? We have no idea.
All answers and tips are welcome!
/dougue
We are the new owners of a charming functionalist house built in 1940. The structure is made of brick and the walls are plastered with (what we believe is) lime plaster both inside and out. On the outside, there is lime plaster on the brick, and they have also applied lime plaster from the inside.
Inside, they have put up some kind of paper-covered thin polystyrene (about 5 mm) on the plaster on the walls facing the outside. On the polystyrene, wallpaper has been applied, which seems to have stayed well since the 80s, except for areas where it has come loose where furniture was pressed against the exterior wall.
As the enthusiastic amateurs we are, we have started renovating what will become the little girl's room, opened up the old vent (all vents in the house were sealed from the inside before they applied the polystyrene on the walls), and removed the wallpaper, but we don't know what to do with the polystyrene. Our instinct is to remove it as we can't see its purpose, but someone must have had a reason for installing it.
- Could it have been installed as interior insulation? The house is listed and cannot be insulated from the outside (the polystyrene would then be the only insulation we've found in the walls), but the listing was done in the 2000s, likely long after the polystyrene was installed, so the insulation theory seems unlikely. 5 mm shouldn't really make any difference in terms of insulation, right?
- Could it have been installed to protect the exterior walls against thermal bridges/microclimates when furniture is placed along the wall? We've seen dark spots on the wallpaper where furniture was previously placed tightly against the exterior walls. We've heard from others with similar stone houses that this can happen if furniture is placed directly against the exterior wall.
- Could it be some kind of 80s version of renovation wallpaper applied to enable wallpapering on the exterior walls? On the interior walls in the same room, they have applied the wallpaper directly on the plaster (looks fine and sticks well), but maybe it adheres less well on cold exterior walls, which is why they used the polystyrene?
This polystyrene has been applied to the exterior walls in all rooms except the bathroom, toilet, and a larger room upstairs. In that room, the wallpaper looks as fine as in other rooms. We've Googled and asked construction firms that have been here for other reasons, but no one has seen this solution before.
Can anyone help us shed some light on the polystyrene's purpose? Why is this type of polystyrene used on exterior walls, and most importantly - should we keep it? Replace it with something else? Remove it and wallpaper directly on the underlying plaster? We have no idea.
All answers and tips are welcome!
/dougue
Know-It-All
· Västra Götaland
· 12 294 posts
It is additional insulation, keep it otherwise you'll "double" the energy consumption.
Know-It-All
· Västra Götaland
· 12 294 posts
Is it only 5mm? I thought it was foam and then 5mm gypsum or something. 5mm doesn't make much of a difference.
Thanks for the response!Ljus said:
Paper-clad polystyrene around 5mm!
Could it be a layer of 6mm renovation plasterboard?
But the fact that several companies have been on-site and haven't seen anything like it speaks against it
By several companies, I mean two, but they were here for a ceiling issue so they might not have looked much at the walls before
At first, I thought it was plasterboard because the polystyrene is clad in the same type of gray paper as plasterboard, but the paper came off a bit in a couple of seams when we removed the wallpaper, and then we clearly saw that it was polystyrene behind it. You can also feel it when you press on the wall; it's a bit soft behind the paper. I pressed a knife into the paper but hit plaster after just a few mm. When we then removed the wallpaper in the window niche, we saw the seam in the polystyrene and measured it to 4-5mm.
No, there
No, no gypsum. They've glued this paper-covered polystyrene directly onto the underlying plaster. It's 4-5mm thick (or rather thin?). But it might make a difference for the heat anyway. They probably couldn't have put it thicker without removing baseboards and replacing window sills (it's like they've put it as wallpaper on the plaster without removing baseboards or doing any extra work at all, it seems), otherwise the polystyrene would stick out above the baseboards and around the window sills. Maybe they thought 5mm is better than 0mm.
Can be a comfort-enhancing measure to remove the cold feeling from the walls.
In terms of energy, it doesn't make a difference either way.
I would have taken it down and plastered and painted, creating a nice feeling with plastered interior walls.
In terms of energy, it doesn't make a difference either way.
I would have taken it down and plastered and painted, creating a nice feeling with plastered interior walls.
Hello and thanks for your response! That actually sounds like a reasonable theory, these walls probably do feel a bit warmer in comparison.L Lutte said:
But do you mean we should paint directly on the plaster? What should we paint with in that case? Isn't there a risk of it becoming patchy/drawing differently considering there might be glue residues left on the plaster? They have also patched several smaller holes with sloppy darker cement putty about 10×10 cm per hole - is there a risk that these will show through if we paint directly on the plaster? Should we apply an additional fine layer of plaster to paint on in that case?
Sorry for the thousand questions but we are not very experienced with plaster so we're trying to learn as we go so to speak. We were otherwise thinking of putting a renovation wallpaper on the plaster and painting directly on this. Didn't even consider that we could paint directly on the plaster