Message text written by "BP - \"Is this the list with all the ivy haters?\"" >could I pour low cost walls for the garden lets say using acetic acid and this unstable Gypsum (sulphur % said to be low) then waterproof the walls...or is this a waste of time.....and go back to the cement....< Given the probability that there will be contact with damp soil, and more than light moist exposure, I'd recommend using the cement. Find a nice dry interior use for the gypsum. Mike E.