On Oct 8, 6:21*pm, wrote:
I have a retaining wall outside that I've been modifying lately, it's
about 50' long and 3' high. Currently it's constructed out of just old
pressure treated 2x12. I would like to build a faux rock wall. I think
that would look much better. My questions are, is faux rock the
correct term? Second, what do I use for backing? Can I mortar the rock
to the pressure treated wood then grout? Any good websites where I can
find more info? I Googled faux rock, but didn't come up with too much.

First what you have is a fence not a true retaining wall, so you are
trying to face a fence with synthetic rock. I may last a couple years
but eventually the wood will flex/swell/shrink/bow/cup/pushout and if
the rock doesn't fall off the morter will crack out. I cant think of
anything good coming out of what you want here nor a "good" way to do
it, anything you do here is a compromise.