Sounds like you have a light intended to mount over a flush box and it won't be very weathertight if mounted over a surface box.I have a light on a block wall that’s needs a weather box so I can run conduit up to the ceiling to feed another light. The problem is the light wraps around the weatherproof box slightly covering the 1/2 inch hole. The conduit will not fit. I was trying to find a deep box with the hopes it would work. Thanks for the reply.
Jim
or sleeve box with 4" PVC coupling cut to match depth of boxA cheat (that may be rejected by code officials) make a flat oversized plate to fit the box with wiring access hole in center, then attach luminaire to the plate.