2×6 ft blue Ground nstruction mats 100 T load capacity In the case of a deck, this would be the weight of people and pets on top of the deck. For a deck with a maximum live load of 40 pounds per square foot and a dead load of 10 pounds per square foot (for a total load of 50 pounds per square foot), the maximum span is 9 feet 5 inches for a No. 1 quality 2×6 joist spaced 16 inches apart.