Proper sizing and spacing of the deck joists will support the decking without sagging or failure.

• Maximum floor joist spans are determined using the size and species of the wood, the live load, and the on center spacing of the joists.
• Maximum cantilever is determined using the size and species of the wood, the live load, and the back span of the joists.
• Ends of the joists must bear 1-1/2″ on wood or metal, and 3″ on masonry.
• Joists bearing on top of a single ply beam or ledger need to be attached with a mechanical connector.
• Joists attached to the side of a beam or ledger needs to be supported by an approved hanger.
• Lateral restraint needs to be provided at joist ends and bearing locations to prevent rotation.
• On center spacing of the joists is determined by the thickness of the wood decking, the number of joist spans, and the orientation of the decking.
• For plastic composite decking, the on center spacing of the joists needs to be in accordance with the manufacturer’s instructions.