Flooring Tile - prep for tub surround

A question about tiling a tub surround...

We're doing the finish work on a bathroom remodeling project The contractor hung cementboard for the tub surround. Around the plumbing locations--faucet, showerhead, 2 hot/cold controls--he left 2-1/2 inch holes where the much smaller piping protrudes through the wall.

Should I be concerned about water flowing or seeping around those holes? It's been suggested that I need to use fiber-mesh, thinset, and some sort of vapor barrier around the pipes. Do you think I ought to do this? And how would you recommend doing it?

Why such big gaps?Are there escucheons going on after the tile?Try and get him to make these holes smaller if possible,and how big are the tile ?if small tile then i would be a little concerned about the coverage,meaning the amount of tile that will be stuck to the cementboard with nothing behind it for support.If a larger format tile then i would be less worried but see if you can get him to fix the holes :cool: