I live in an attic, and the head part of my bed is in a corner where the roof slope, an outer wall and the wall to the neighbour's unheated attic meet. After a few winters of waking up to the feeling of the roof slope sucking the warmth out of me, I got a pack of polystyrol inner wall insulation. Unlike traditional styrofoam, it is a homogenous foam on the inside, similar to polyurethane foam. On the outside, it has a matte finish with a very fine paint-like structure.
I nailed the plates to the wall, right over the existing structured wallpaper. Then I filled the seams and the nail heads with acrylic caulk. Now I'd like to give it a finished look.
I feel adventurous enough to try a wallpaper. I have never applied wallpaper before, but it seems that the new cellulose-fleece-backed type is very easy to work with.
The problem is that the Internet tells me that regular wallpaper glue won't stick to regular styrofoam. I didn't find information specific to the glue for cellulose-backed wallpaper, or about this finished styrofoam. I also found the information that wallpaper can be applied to styrofoam in the following order:
- a layer of styrofoam glue, left to dry out
- a layer of underwallpaper soaked in normal wallpaper glue
- a layer of standard wallpaper, applied in the standard soak-in-glue method
This information came from the site of Henkel, manufacturers of styrofoam glue which costs 7 Euros per kg, an amount which only suffices for 1-2 square meters of wall.
Before I pay for glue two times as expensive as the styrofoam below it and three times as expensive as the wallpaper above it, I'd like to know:
- Is a base layer of styrofoam glue the only way to get wallpaper to hold to the styrofoam?
- Do I really need an underpaper layer if I am using a cellulose-fleece wallpaper as opposed to a standard one? Does it help hold the real wallpaper to the styrofoam, or is it just to give a nicer look?
- All articles I read agree that it is possible to paint over styrofoam using regular water-based inner wall paint. Could I paint over the styrofoam and apply wallpaper to the paint? It would cost three times less than the styrofoam glue.
This is what the caulked styrofoam looks like right now:
Best Answer
You should not do this. Foam insulation (EPS, XPS, etc.) needs to be covered with drywall in order to protect it (extend the amount of time before it melts) from fire. Otherwise you are risk of being exposed to toxic fumes and melting foam should you ever have a fire. Imagine molten foam dripping from your ceiling onto you - not a situation you want to find yourself in.
The correct "solution" is to drywall on top of the foam (using furring strips, or long screws into the studs), mud/tape the drywall, prime, and then apply wall paper using standard wall paper adhesives.