Hey all   My architect has spec’d edpm but talking to some roofers they say that’s the wrong way to do it and should be grp ..   So I’m not sure now !   My flat roof can be parked on and has 4 skylights .   so bottom up structure is :   reinforced concrete  high compressive insulation  osb ? If using edpm or just grp  reinforced poured concrete  chippings  sand  driveway blocks    I guess the risk with edpm