I am remodeling a bathroom to add a shower to a previously tub only bathroom. It is an older home (Built late 40's) and I believe the two interior walls are lathe and plaster the exterior wall I believe is cinder block with a plaster finish. The walls are not perfectly flat there is some minor bowing.
Can I apply the tile directly to the plaster without adding cement board? How much bowing is too much to fix with quick set? Any other words of advise?