I'm working on installing hand rails in a shower. The walls are covered by = cultured marble slabs with drywall behind the marble and then a 1 inch or s= o space for insulation, and then block behind that. My plan was to drill in= to the block and use lag shields to hold the bar in place. This worked on o= ne end of the bar but it seems the block split apart when I bolted the othe= r end. What I have now is one end of the bar secure with a lag bolt and a 5= /8 inch hole in the marble and 1/2 inch hole in the block where the other e= nd is supposed to mount.
I thought about piping in a stiff mix of thinset using a grout bag and then= redrilling the hole and using a lag shield again but I just don't think it= will hold up. I can probably get a butterfly anchor in the insulation spac= e behind the drywall, but is this the best way to go?