I am making a raised platform for a garage for storage of heavy items. I am thinking of using 175x50 joists spaced at 600mm (area of platform is 1800 L x2700 W ) with 50mm joist hangers and 18mm T&G chipboard for the deck. I assume it would be best to use joist hangers that are designed to be cut into the wall but do the hangers need to be secured to the wall with screws or will the joists and chipboard lock everything in place ?