Skim-Floating to Smooth a Heavily Textured Wall

Texture looks bad under wallpaper, and in interferes with good adhesion. The walls must be smoothed before the paper can go up. Very similar to popcorn texture but not as thick, this sand type finish still sticks out from the wall in some spots as far as 1/4″. That leaves a lot of space between those grains of grit for me to fill in with smoothing compound.

Here I’ve used a putty knife to knock off the tops of those grains of sand. At the top half of the photo I am applying the smoothing compound. I use a trowel to do this. It’s slow and labor-intensive, but it gets my eyes close to my work, and it gives me the best control. This had to be applied so thickly that it will take probably two days to dry. Having the air conditioner or heat running helps pull moisture out of the material. Once it’s dry I will sand it smooth, and then prime it for wallpaper.

I like Sheetrock’s Plus 3 lightweight joint compound for this task. It adheres well and sands easily. The regular version (in the red, white, and green box) is very difficult to sand. Hot mud or quick dry or 20 minute mud should not be used, as primers and pastes don’t stick well to them.

Danger Signs of an Unstable Wall Surface

These nails were holding picture hooks to the wall. The hooks had an adhesive backing. When they were removed from the wall, chunks of latex paint stuck to them and pulled away from the wall, revealing a crumbly sub-surface. This is bad news for wallpaper that might be hung on top of this.

Other spots. What happens is, this is a 90 year old house. Over the years, many coats of paint and other surface treatments have been applied to the walls of this dining room. These coatings are not necessarily compatible with each other. Plus they may have been applied without the proper surface preparation. Oil based paint, then latex, then someone rolls on a gloss paint, the next guy follows with latex but neglects to de-gloss the previous layer so the new layer doesn’t really stick well.

Somewhere along the line, something got chalky. Here you see I have wiped crumbly chalky substance from inside the wall. This is why the latex paint is not adhering well and pulled away so easily. Nothing sticks to dust or grit or chalk.

Gardz is cool stuff. It’s a penetrating sealer that soaks in and actually binds crumbly materials together, drying into a hard, solid mass. The problem here is, it won’t penetrate the paint that is on top of the unstable layer, so we’re still dealing with a wall that has potential to come apart (delaminate).

Gardz applied. You can see how it has soaked into the porous areas, but is sitting on top of the latex paint.

The problem with an unstable wall and wallpaper, is that, as wallpaper sits on a wall and the paste dries, the paper shrinks just a tad, and this shrinking puts tension / torque on the wall beneath it. Sometimes this is actually powerful enough to pull the layers inside the wall apart, resulting in seams that split open.

These are not “loose seams,” but the paper actually taking layers of paint and dust along with it. Really can’t be repaired.

So best to find a way to prevent it from happening in the first place. More on that later.