Hello. I have a small half-bath with 1" tiles on the floor. When we gutted the bathroom and put in new walls they were left about 1.5" back from the floor edge, leaving that amount of exposed sub floor around the perimeter of the floor. Instead of tiling the perimeter we are going to put in a border of river rock on the floor.

What should I use to put the river rock into? Would I use the same adhesive for tiling the floor and then grout on top of the rock?

Thanks for any suggestions.

I am confuesd, by redoing a room how did the walls get set back so much? If I were to set river rock I'd use masons mortar, type N or type S cement.

The previous owner had 1/2" plywood nailed to the plaster which brought the wall out away from the studs farther than usual. He then tiled the floor up to the plywood. When I gutted the bathroom and removed the plywood, plaster, and lathe boards and then put up new drywall right to the studs, that's where the gap comes in.

When I use the mortar, should I then apply grout once the mortar sets?

Thank you.

I'd practice on a scape of plywood but you can set the rocks in the mortar and the mortar squishes up between the rock when you press them in, it kind of makes its own grout. Does this make sense to you? You could also buy a tile border or bullnose to put around the old tile making a contrasting edge.
Thanks,
Bob