Spray foam board feet and 2-inch lifts explained
Foam kits are sold in board feet: 1 sq ft × 1 inch = 1 board foot, so board feet = area × thickness. Spray closed-cell in ≤2″ lifts (it cures hot) and budget 70–85% of a kit’s rated yield.
What this diagram shows
How spray-foam quantity works. One board foot is one square foot sprayed one inch thick, so board feet equals area times thickness — for example 150 square feet at 3 inches is 450 board feet, which needs one 600-board-foot kit. Closed-cell foam must be applied in lifts of no more than 2 inches per pass, letting each lift cure first, because it cures exothermically; too thick in one pass chars, shrinks, and pulls away. Budget 70 to 85 percent of a kit’s nameplate board feet for real-world yield.
Spray Foam Calculator
Spray foam take-off — board-feet, kit count, R-value, IECC compliance, vapor class. Open vs closed-cell. IRC R806.5 / R702.7 callouts. Free.
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