Most composite and PVC decking brands, like Trex and Azek, recommend a maximum joist spacing of 16 inches OC. Some brands, like WearDeck, let you get away with more – reinforced with a layer of fiberglass on both the top and bottom, WearDeck boards easily allow for spans of 24 inches OC.

How far apart should Trex deck boards be?

Important points about gapping All deck boards must always be installed with a 6mm side-to-side gap. The Trex Hideaway Hidden Fasteners automatically measure the 6mm gap between grooved edge boards but you must still ensure the 6mm gap with the square edge boards.

How far can composite decking overhang?

Overhanging composite decking is an important element to the deck’s design for aesthetic reasons and protection of the deck’s substructure. Most composite decking should overhang the deck’s substructure ¾” (18mm) but may be limited to only a 1/2″ (12mm) or as great as a 1 ½” (38mm).