I just started my bath renovation and have been trying to take the room down to the studs. The first layer is an icky fake tile paneling. I got that removed on the first wall and removed a heavily wallpapered sheetrock wall to expose the studs. I'm now working on the second wall; something is different here. Under the fake tile paneling is a layer of green board and under that, something like cement. I believe it is plaster. The window is flush with this material. The wall is an exterior-facing wall and the house, which was built in the 1940s, is made of some kind of masonry block. All the walls in the front of the house and all of the other exterior-facing walls are plaster.

I'm concerned that if I try to remove the plaster or cement layer that I've encountered I will eventually find lathe but no wood studs on which to install new drywall. So far, the plaster or concrete appears to be in good shape. The green board was only glued on.

This wall also composes one of the short ends of the tub surround. I had initially planned to install Go Board in the shower surround area and drywall elsewhere, but now I have a dilemma. If I replace the drywall that was on the wall outside the tub area and around the window, it will be 1/2 inch higher than the window and there will be no way to frame it. Since I need a waterproof shower and tub surround, I will need to install Go Board or a similar product in that area. I'm thinking the best thing to do with the plaster is to skim-coat it and try to make it look like the plaster elsewhere in the house. Or I could try adding a top layer of plaster, but if I go with one of those options, the Go Board will leave a 1/2-inch raised edge from the plaster, and even more of a raised edge after it is tiled. Would this pencil tile be a good option to make the raised area look intentional? I am using white 3 x 6 subway tile in the tub/shower surround and this mosaic tile for the niche and trim edged with the black pencil tiles, which I also planned to use to trim the exposed edges of the subway tile where the shower surround ends.

I was thinking about laying the pencil tile with the bottom against the Go Board since all sides except the bottom are finished. Or would a Schluter edge be a better option? (I'm not a fan of Schluter edging but this might be a good use for it.) Or does anyone have another suggestion that would accommodate framing the window and tiling the shower surround?

Yes, I know it's ugly! That's why I'm trying to renovate.