Looking for help with creating new installation guidelines. Chicago Public Schools is trying to create new guidelines for the installation of outdoor mosaics. 

They want to project the brick walls of the schools so they want a 1/2" gap between the mosaic and the wall so the brick can breathe.  

Does anyone have guidelines used by their institution? 

Their plan involves using marine grade wood planks, then 5/8" Dens Element Fiberglass Gypsum Sheathing, then Wedi board, then the mosaics. 

We are thinking of an aluminum frame and Wedi board but are not sure what to use in-between. Plus, it is a free form shape and we are not sure what edging to use. 

Any advice would be appreciated.