Deck Maintenance Calculator

This calculator starts from a base re-staining interval set by material — pressure-treated pine and redwood at 24 months, cedar at 18, and composite at 0 since composite decking is sealed at the factory and never needs staining. That base interval is then scaled by sun exposure: full southern exposure accelerates UV breakdown of the stain film, cutting the interval to 75% of baseline, while a mostly shaded deck stretches it to 130%, with a 6-month floor no deck should exceed regardless of shade. Gallons needed comes from a coverage rate of roughly 250 square feet per gallon for semi-transparent stain, reduced for decks over 5 or 10 years old because weathered, more porous wood soaks up more product per pass — so an older deck of the same size needs more stain, not less.

Annual cost combines the per-application stain cost (gallons times roughly $35) spread across the year's expected number of applications, plus a flat annual cleaning charge; composite decking instead uses a simple per-square-foot cleaning-only cost since there's no stain to buy. Total lifespan is set by material (20 to 35 years) and nudged by sun exposure in the same direction as the staining interval — full sun trims 15% off expected life, deep shade adds 10% since less UV and thermal cycling means slower material fatigue. The biggest assumption to know: these are typical-conditions estimates, not a substitute for a physical inspection, and the "next stain due" figure assumes a clean, uninterrupted maintenance history rather than tracking your actual last application date.