I would like to make a corner garden bench seat with attached planters behind the bench seats similar to the attached. I intend to build a wood frame and I am sure in my research I saw recommendations for the use of fibre cement board to clad the planters (although I cannot find this info now). Would this be the best material to use? Also, would the fibre cement board be the final finish or would it require a coating or render to be suitable in the garden? Any advice would be appreciated, thanks.