Sanding bathroom wall to put tile

Hello there,

I’m on a DIY bathroom renovation adventure here and I’m at the point to prepare drywalls and concrete floor for tiling.

The problem is that the wall wasn’t fully painted and there is quite a gap that I need to level. This gap seems to be really to the drywall (if it’s not the drywall itself).

My question is:
Should I sand the whole wall to level it to the gap that I think is the drywall or should fill the gap with something and sand them both to match afterwards?

I’ve attached some pictures of the walls that I’ll be preparing / tiling.

Any help is welcome 🙂 Thanks!

 

I'd use Durabond and a 12" wide plaster trowel or taping knife.
.

 

So you would fill the small area to match the other and would sand them even. Is that correct?

 

Will any of the tile be in a wet area such as a shower or tub?

 

No. It's one a half bathroom. there will be just the toilet and sink.

 

Much easier to fill the voids so they are level than sanding!

 

I agree filling and floating it out so it appears to be even is best. Latex paints don't sand well. Adding mud and then sanding is a lot less work.