

Top photo: A small circle of paint had been pulled away from the wall. When I picked at it, I was able to easily detach more paint.
Second photo: When I removed the light switch plate, some paint had stuck to it, and pulling the switch plate off the wall took some of the paint underneath along with it.
The exposed wall underneath the paint was gritty and dusty. I could not tell if it was a layer of old paint, drywall, dust, residue from ancient wallpaper paste, or other. I had the feeling that if I had tried, I could have peeled all the paint off the dusty subsurface.
This is not good.
This is an old house, and many layers of paint and other treatments have been added to the walls over the decades (100 years!). Many of these substances are not compatible with each other, and especially not if the walls were not prepped properly before applying another coat of paint.
Latex paint won’t stick to oil based paint. New paint won’t stick to a glossy paint. Nothing sticks to a dusty surface.
All these various materials will adhere to one another – for a while. But when a stressor is added to the formula, there is the potential for the layers to delaminate (come apart). That’s what happened in the two areas above, when a bit of a tug was all it took to peel several layers of paint away from the wall.
The issue here is that wallpaper comes with its own stressors. Wallpaper gets wet when it’s pasted, expands a bit, and then when the paste dries, the paper shrinks a tad and puts tension on the walls. Over time, with changes in temperature and humidity, foundations shifting, and just plain old passage of time, this tension could cause the paint to give way from the walls – this usually manifests at along a seam.
I use a wallpaper-specific primer, and among its attributes is the ability to withstand this type of tension.
Let’s hope that over the years, the many layers of paint, the new coat of primer, and the wallpaper all work together to stay nice and tight to the wall.
Note: If I had known about the wall condition earlier, and if the homeowners’ budget had allowed, a liner would have been a good option in this case. A liner is a special type of paper that is applied to the primed wall the day before the paper goes up. It serves several purposes, but one is to distribute tension across the wall. Because the seams of the liner do not line up with the seams of the wallpaper, drying and shrinking wallpaper puts tension on the liner, and not onto the unstable wall itself, thus pretty well eliminating the chance that the wallpaper seams could cause the wall to delaminate.
The downside is that using a liner adds an extra day (or more) of labor, plus the cost of material.