No, you don't need to fill in the spaces between the tile and shower fixtures. Since you've stated that the escutcheons / flanges will completely cover the gaps, all you have to do is caulk the escutcheons and flanges all the way around after installing them. You'll also want to caulk around the spout where it meets up against the tile.
Answer from JACK on Stack ExchangeSo I completed my tile around my bathtub, however I am trying to determine if I should of left a bigger opening for my shower valve. I the trim pieces I have 'dry fitted' appear to be away from the wall.
Before moving forward, should I remove the tile around the pipe to make a bigger hole for the valve, trim. My thinking is in the attached image around the circle.
If so, any advise on how to remove. I have a grinder, but not sure it that would tear this apart or not.
Trim piece added.. for sizing.
The pencil circle is where the inner part is on the trim piece (other picture). NOT the otter circle.
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The shower valve trim will always go over the tile.
Usually the trim will have a foam backing ring that should compress against the tile and prevent water from getting behind it. If the tile is uneven or you do not feel comfortable with the seal of the valves built in foam gasket you can caulk around the trim with a latex caulk. we usually use white or clear for the caulking but it depends on your tile/ grout colors. If you ever need to access the ports on the valve behind the trim you simply cut the caulking with a razor knife and remove the trim.Simply clean off the caulking and re-seal the trim again after you make your adjustments to the valve.
The trim goes over the tile and covers the hole. Caulk around the edge to seal it from the water. Leave a little spot at the very bottom uncaulked as a weep hole.