Composite vs. pressure-treated decks: true lifetime cost and ledger board safety

Composite decking costs more upfront, but pressure-treated wood demands continuous staining. Here is the true 20-year cost breakdown.

Ledger board flashing: The #1 cause of deck failures#

Over 85% of deck collapses stem from improper ledger board attachment to the house. When bolted through siding without stainless steel Z-flashing and waterproof membrane, water rots the house rim joist unseen.

Finished raised composite deck with aluminum railing — 20-year cumulative ownership cost (400 sq. ft.): pressure-treated lumber vs. capped composite.

Decking materials 20-year comparison#

Deck Material	Upfront Cost (300 ft²)	20-Year Maintenance	Expected Lifespan
Pressure-Treated Wood	$19,500–$26,500	$6,000–$9,000 (stain + repairs)	15–20 years
Western Red Cedar	$21,500–$29,500	$7,000–$10,000 (oil & seal)	20–25 years
Capped Composite (Trex/TimberTech)	$27,000–$36,500	< $1,000 (wash only)	30–50 years