Determine the shower's size and location on the rear or side of the house. Mark out the back wall of the shower on the side of the house using a measuring tape, pencil and level. Use a circular or reciprocating saw to remove the siding or shingles and expose the house's interior walls. Hire a plumber to run hot and cold plumbing to the site.
Cover the exposed wall area with cement board, which acts as a moisture barrier and provides a masonry surface for the tile and thinset to bond to. Make sure to mark and cut openings for the plumbing hardware. Secure the cement board to the side of the house with screws. Cover seams with mesh tape and a skim coat of thinset.
Plot out the dimensions of the concrete pad using stakes. Excavate the area to a depth of 8”. Use 1" x 4" boards to create forms to hold the wet concrete. Pour gravel to a depth of 4” and tamp down to a level surface. Prepare pre-mixed concrete according to manufacturer’s instructions and pour it into the form. Work the concrete with a trowel until it is smooth and has the desired pitch. Let it cure for several hours.
Mix latex modified thinset according to manufacturer’s instructions. Using the flat edge of a notched trowel spread a thick coat of thinset up the wall of the house to a height of 12". Use the notched side of the trowel to even it out. Start setting stacked river rock tile at the bottom corner and work up. Make sure to push the stones securely into the thinset. Continue setting thinset and laying tile until the wall is completely covered. Be sure to work around the holes for the plumbing fixtures.
Spread a coat of thinset around the perimeter of the dry concrete pad. Leave a gap if you desire an entranceway flush with the pad. Begin setting glass blocks into the thinset at the corners. Butter the side of subsequent blocks on one side before setting in place next to previous block. When setting the blocks always check for level and plumb. Continue until the block has been laid all around the base. Let dry before moving onto river-rock floor.
Starting in one corner, apply a layer of thinset across the top of the concrete base. Gently push the first river rock mesh square into the thinset. Continue setting thinset and laying tile squares until the surface is completely covered. After all the tiles have set up for four to six hours, mix grout and apply with a float. Push down firmly to ensure that the grout gets in between all of the individual pebbles. Immediately wash off excess grout with a damp sponge. Have a bucket of clean water handy to rinse the sponge frequently.