Joist hangers secure the floor joists of a new deck to the beams that form the outer edge of the deck. They allow the joists to buttress up against the outer beams and attach securely. Joist hangers are strong and will keep a floor strong as the wood ages and warps over time. They make joists stronger than they would be if the joists were attached to the beams with nails alone.
Measure across the outer beam and determine the spacing for the joist that will support the decking planks. Measure across the beam and place marks at each point that a joist will be placed.
Take a joist hanger and place it straddling one of the marks with the mark at the centre of the joist hanger. Nail the hanger to the beam on both sides to secure it. Make sure that you place a piece of scrap joist material in the hanger so that you get the correct spacing before nailing the second side of the hanger to the beam.
Cut your joist and fit it into each of the hangers. Make sure that the joist fits correctly and is not short. You need the strength of the joist as well as the added strength of the hanger to form a sound, strong deck.
Nail the hanger to the joist at the two points on each side of the hanger.