Wallpaper – Poor Adhesion Issue Due to Dusty Walls

The existing wallpaper in this sink / vanity room of a hall bathroom is unique, because instead of coming in rolls, it came in pieces of torn paper, each about the size of a paper plate, that were placed on the wall in random ways, with the pieces overlapping each other.  This was a fairly popular wallpaper option back in the ‘90’s. 
I’m to hang new wallpaper in this room, so my first step was to remove the torn paper.  

This started out seeming easy, because the paper was literally falling away from the wall – but only around the top, and only the top 5” or so.  The lower areas were stuck nice and tight to the wall. What’s going on?

The original installer hung his wallpaper directly on new drywall / Sheetrock , with no primer and no other prep.  Turns out that, under this wallpaper, there are actually several different types of wall surfaces related to the new drywall.  

The main part of drywall is grey in color .  But here you see a band of white running along the top of the wall, under the ceiling, about 5” wide.   This is where the joint compound was applied , to smooth over joints , drywall tape , and nail heads . 

But the curious thing is that the wallpaper is adhering to the drywall – but not to this white band of joint compound below the ceiling line.
The reason?  After the drywall guys sanded this area smooth, no one wiped off the dust left over from sanding .  Thus, there was  a layer of dust on the wall, between the wall and the wallpaper.  Well, the wallpaper paste wants to bite into a solid surface, and it can’t get a grip on dust.  That’s why you see this top portion pulling away from the wall. 

I have a lot more prep to do in this room.  But before moving forward, I took a sponge and bucket of water and wiped the dust off that top portion of wall.  Now I’m assured that any smoothing compound or primer or wallcovering or other that is applied, will stick . 

For reference, here’s a shot of the un-primed drywall being uncovered as I strip off wallpaper in another area.  This picture shows the sections of drywall , joint compound , and also paint (from overspraying the woodwork ).  Wallpaper adheres to all these different surfaces in different ways.  Another reason to always use a wallpaper primer – it will adhere to just about any surface, and will create a uniform coating for the wallpaper to adhere to. 
I like Roman Pro 977 Ultra Prime.

Contractor Prepped Walls – But Left Dust

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 .