Build a River Rock Shower
by Dorothy Ainsworth
I had always wanted a river rock shower...who knows why. We all have our idiosyncrasies. Maybe it just sounded like a beautiful idea. Maybe it conjured up images of two lovers washing each other's hair to Rossini's Barber of Seville, surrounded by walls of a thousand stones, and the shampoo sitting on its own little rock ledge. But whatever the reason, I knew I was a hopeless romantic and would still want one, even when I got to the age where I should be wearing a helmet in the shower!
I finally got my chance to go for it while finishing up the rebuilding of my log house after the first one burned in 1995. It would have been much easier and cheaper to use tile, but I knew that if I built what I really wanted, I'd cry only once. So I started in, not quite knowing where to begin.
Over the years I had collected a pile of small, smooth, flat river rocks, but cumulatively they were extremely heavy. Since this shower was in the loft bathroom, and even though the floor was supported by 4" X 10" beams, I'd have to consider weight.
I had heard of cultured stone (pumice and portland cement) cast from molds made from river rocks, but only half the weight. I looked in the yellow pages and found the local distributor for cultured stone products. They showed me samples, and I was delighted to see that each stone looked exactly like a real river rock but was flat on one side for ease in installation. They also gave me a leaflet of how-to instructions but warned me that they had no data on showers, so their 30-year warranty would not apply. I didn't care...I'd take the chance. Their stonework holds up outside in the rain; what's the diff?
I had already built the shower walls out of 5/8" plywood attached to 2" x 4" studs (around a 3' x 5' shower pan), so I measured the square footage and ordered 9 boxes of their smallest stones, called skimmers (each one about the size of my clenched fist). Each box, called a handipak, equaled 8 sq. ft. and weighed about 90 lbs. The total cost was $600.
Following the instructions, I installed a vapor barrier over the plywood. I chose roofer's Stormshield...tarpaper with a sticky backing...but regular tarpaper or heavy gauge (6-mil) plastic sheeting can be used instead.
Then I covered the plywood with cement board (Wonderboard) and caulked the seams and screws, then fastened sheets of metal lath (2.5 lb. galvanized diamond mesh) to the cement board with small washers and screws. The mesh creates a textured surface to grab the mortar.
I was advised by the Cultured-Stone tech line to apply a scratch coat of mortar 1/2" to 3/4" thick on all 3 walls of the shower first, texture it with a 1/4" notched trowel, and let it cure for at least 48 hours before laying up any river rocks. Using that method, I could take my time installing a few rows of rocks whenever I felt like it, by mixing up a small batch of mortar each session to butter the rocks and pressing them against the scratch coat. Sounded good to me.
I bought six 94 lb. bags of Cultured Stone company's recommended Type-S mortar and mixed up 1/2 bag at a time to the consistency of peanut butter, dyed it a terra cotta color with iron oxide powder, and troweled it on with a tremendous expenditure of energy but no real skill. A lot of it fell off and made a huge mess that included permanently staining my shoes to look like feet of clay.
Because cement starts to harden within one hour, there was no time to lollygag. I quickly developed my own technique for forcing cement into the metal mesh. Using rubber gloves of course, I scooped up balls of mortar and threw them as hard as I could at the mesh: splat, splat, splat. After splatting on a row or two, I troweled it nice and smooth to about 5/8" thick, then raked it horizontally with the notched end of the trowel. Thank goodness no one saw me in action, but the end result was great!