I usually insist on prepping the walls for wallpaper. But we had a time crunch here, and the homeowner asked her paint contractor to strip the old wallpaper and smooth the walls. He did a good enough job of skim-floating and sanding the walls smooth. Unfortunately, he neglected to wipe residual dust off the walls. The problem is that nothing sticks to dust. Not paint, not primer, and not wallpaper. Over time, stress, humidity, and other factors can cause the wallpaper to expand and contract, which puts tension on the seams. This tension tugs at the seams , and if the wall surface underneath is unstable ( dusty ), the layers can pull apart ( delaminate ), and you end up with failing seams. So I wiped down every square inch of wall, using a sponge and bucket of water. I rinsed the sponge frequently, to prevent build up of dust on the sponge. Here’s drywall dust wiped off in just a few swipes. In the background, you can see tracks of my damp sponge along the wall. These damp areas will need to dry thoroughly before I can apply my wallpaper primer. A heat gun helps speed that process along. One fear that I have is because, as you see in the photo, the contractor spray painted the woodwork, and in so doing, got a lot of overspray onto the wall. This can be painted over without much problem. But, as mentioned above, putting wallpaper over this can open a can of worms. Even with a good wallpaper primer underneath, the drying / shrinking wallpaper can put stress on the seams. If the wall underneath is dusty, the layers may let loose of one another and result in a popped seam .
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