Formwork Stud / Wale Maximum Spacing
What formwork-tie-load says is sized separately. A form member is a continuous beam over three or more supports, so the span comes from three exact continuous-beam results - M = wL^2/10, V = 0.6wL, and deflection wL^4/145EI - each inverted and the smallest governing. A 2x4 stud under 600 psf at 12-in tributary allows 24.7 in by bending and 41.0 by deflection but only 21.0 by SHEAR, which is the one that governs short deep form members and the one people skip.
Formula and source
w = pressure x tributary / 144; bending L = sqrt(10 Fb S / w); shear L = (2/3 Fv b d)/(0.6 w); deflection L = cbrt(145 E I/(w x denominator)); the smallest governs.
Formwork members analyzed as continuous beams over three or more equal spans, the standard ACI 347 formwork-design approach, by name.
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