As best practices, we would recommend having a space of at least 1/2” behind the boards. This can be achieved via joists. You are welcome to therefore use anywhere from 1/4 to 3/4 inch thickness joist. A 1 by 3, 1 by 4, wood, aluminum, or hat channel would all fit this requirement. The AW08 siding clip would then add another 1/4 inch of space from the wall. This system is required to allow for air flow, which prevents the buildup of moisture on the siding boards.