Labor costs depend on a contractor's specific rates and fees, but a good estimate is $4,200 to $8,400* total on a 14x20 deck. How Much Does it Cost to Build a Composite Deck? - Trex trex.com https://www.trex.com � planyourdeck � deck-cost-landing trex.com https://www.trex.com � planyourdeck � deck-cost-landing Labor costs depend on a contractor's specific rates and fees, but a good estimate is $4,200 to $8,400* total on a 14x20 deck.