Do I need to prime the mud for self adhesive wallpaper?

Question

I've applied the joint compound,sanded it down. Is it necessary to prime the mud before putting self adhesive wallpaper on it? I don't plan on taking it down or painting over it in the future. Would priming the wall change how it sticks etc?

Answer 1

Defer to the wallpaper installation instructions, but absent of that, definitely it needs some sort of paint to seal the joint compound so it doesn't suck all the moisture out of the wallpaper adhesive before it has a chance to set up. In addition, even though you say you have no plans to take it down in the future, I highly suggest you take the time to also apply sizing to the bare walls, as that will also help seal the wall, provide a better surface for the wallpaper adhesive to adhere to, and make the eventual removal so much easier and hassle-free. I can almost guarantee that if you live there long enough, you'll want to take it down and replace or paint. Even if you don't do that, a future occupant certainly will, and will thank you for making their life a lot easier.

Answer 2

I'd defer to any surface preparation instructions given by the wallpaper manufacturer, but.. My experience has been that other pressure-sensitive adhesive things (post-it notes, masking tape, etc) stick far better on painted drywall than on bare drywall. Maybe it has to do with the surface of the paint; maybe (likely) it has to do with the paint encapsulating the joint compound dust particles. I'd expect primer (as opposed to finish paint) to still be a better substrate compared to bare/sanded drywall.

As always, you can test an application of the wallpaper direct to sanded drywall in a small inconspicuous area to find out whether it performs.

Answer 3

Priming has a few purposes. It seals the surface so that any liquids applied adhere better (paint), it evens the appearance of any thin films applied (again paint) by evening out absorption and background, and -this is an important one- it unarms the effect of residual drywall dust by binding it to itself.

After mudding & sanding, vacuuming and wiping or washing the walls there may still be residual dust in micro-pockets of the finishing drywall coat.

Moreover, priming can reveal any unevenness of the finishing that may previously have been difficult to see with the bare eye.

Some self-adhesive wall paper allows for repositioning, which in turns requires a non-porous and non-matte substrate like a primed or painted wall.