: : I will be replacing my bathtub soon and have been looking at some books on the topic. Some show metal flashing around the top edge of the tub. How necessary is this step, and is this what pros do? Also, should the wallboard sit right on the edge of the tub, or should there be a slight gap between the tub and the wallboard?

: Brian,
: You will want to have a tile flange at the edge of the tub where it meets the wall. The tile backer goes over the flange or in some cases above the flange depending on how far out the flange sets. If the tile backer is allowed to touch the tub deck, it will "wick" water up the wall.
: Leaving a small gap between the hard surface and the tub will allow Silicone to be used as the "go-between" joining tub and wall. There will be some movement, so the flexible sealant is a good way to go.