[mhannam]

I've removed all the old old tiles from the shower walls but there's a little bit of texture and some thinset left on the bed. Overall the plain is pretty flat.

Can I add new thinset and tile right on top of this? Should I add a layer of smooth thinset then tile?

Also, are big tiles or small tiles more forgiving for shower walls? (this is my first rodeo)

Thanks, Matt

 

[oh'mike]

Typically , the backer is removed when retiling a shower--so your question is not a common one.

Is the backer completely sound?

If it is--and you choose to tile over it----this is what I suggest.

First, scrape the surface as flat as possible using a flat drywall knife--

Second---paint the surface with two coats of Red Guard or other surface waterproofer.

Third--start tiling using a powdered modified thinset.

As to tile size----smaller tiles are most forgiving of an out of flat wall---the bigger the tile, the more difficult it is to prevent lippage.