I've been asked to help install grab bars in an (E) tiled shower stall.
What is the best way to do this? Ordinarily I'd drill a hole through the
tile and whatever is behind it -mortar, greenwall, or backer board and
install the grab bar with toggle bolts.

I got to wondering though that if I drill a hole large enough for a
toggle bolt to go through, I might be weakening the wall enough that
holding onto the grab bar might pull some tiles loose, leading to
additional work.

Additionally, the house is an older one, having been built in late 50's
or 60's so it's likely there is a mortar bed - it looks to be the
original tile. If the mortar crumbles around the hole, the toggle bolt
will be pulling on the tile, maybe.

--
charles