Scaffold Tie Spacing Calculator

The Vertical Compliant and Horizontal Compliant checks in this calculator are drawn directly from OSHA's own tie-spacing rule for supported scaffolds, 29 CFR 1926.451(c)(1)(ii): ties must repeat vertically at least every 26 ft for scaffolds wider than 3 ft (every 20 ft for narrower scaffolds -- this calculator assumes a standard-width scaffold and applies the 26 ft figure), and horizontally at intervals not exceeding 30 ft. Total Ties Required is the product of two independent counts -- Vertical Tie Rows (from Scaffold Height, First Tie Height, and Vertical Tie Spacing) and Tie Points Per Row (from Scaffold Length and Horizontal Tie Spacing) -- so widening either spacing input lowers the corresponding count while leaving the other completely untouched: Scaffold Length never moves Vertical Tie Rows, and neither height input moves Tie Points Per Row. Vertical Tie Spacing (ft) and Horizontal Tie Spacing (ft) both move Total Ties Required in the same direction across their full 1-40 ft declared ranges -- wider spacing means fewer required tie points, monotonically, though the relationship steps rather than glides smoothly since row and point counts are rounded up (ceiling) to whole ties. Vertical Compliant and Horizontal Compliant are separate OSHA 1926.451(c)(1) threshold checks against the same two spacing inputs (26 ft vertical max, 30 ft horizontal max) -- they can disagree independently, and widening spacing past either limit flips the corresponding flag to non-compliant without affecting the other. Area Per Tie (sq ft) is simply total scaffold face area (Scaffold Height x Scaffold Length) divided by total tie count -- but whether it rises whenever Total Ties Required falls depends on WHICH input changed.

Vertical Tie Spacing, Horizontal Tie Spacing, and First Tie Height only ever move the denominator (they don't appear in the face-area calculation at all), so for those three inputs the inverse relationship holds reliably: wider spacing means fewer, more heavily loaded ties and a larger area each one must secure. Scaffold Height and Scaffold Length are different -- they move BOTH the numerator (face area) and the denominator (tie count, via the same ceiling-rounded row/point counts) at once, so the net effect isn't reliably inverse. At default inputs, dropping Scaffold Height from 60 to 40 ft lowers Total Ties Required from 15 to 10, yet Area Per Tie stays exactly flat at 280 sq ft, because the tie-row count happens to shrink in the same proportion as the height itself. Raising Scaffold Length from 70 to 106 ft raises Total Ties Required from 10 to 14 AND raises Area Per Tie from 280 to 302.9 sq ft -- both rising together, the opposite of what the spacing-input relationship would suggest.