Bid 18-gauge studs, got told 16: how delegated design eats specialty contractors' margins

Under section 3.12.10.1 of AIA A201-2017, when the contract documents require the contractor to provide design, the owner and architect must spell out every performance and design criterion, the contractor may rely on them, and a licensed design professional must sign and seal the drawings and calculations. ConsensusDocs 200 says the constructor is not responsible for the adequacy of those criteria. Cold-formed metal framing is one of the scopes commonly delegated, lawyers at Peckar & Abramson wrote for ConsensusDocs.

Gauge follows the criteria. ClarkDietrich says curtain wall studs must resist the highest wind or seismic load for the site, with wind pressures usually listed in the general notes of the structural drawings, and that deflection limits are set by the cladding: L/240 for siding or EIFS, L/360 for stucco, L/600 or L/720 for brick or stone. Design pressures from IBC 2012 and ASCE 7-10 onward are strength-level and get multiplied by 0.6 before entering its span tables. In ClarkDietrich's line, an 18-gauge stud is 43 mils of 33 ksi steel and a 16-gauge stud is 54 mils of 50 ksi steel.

The Peckar & Abramson lawyers advise contractors to take on delegated design risk knowingly and price it, or to limit it in the contract. For a framing subcontractor that starts in the proposal: list the wind pressure, deflection limit, stud depth, spacing and gauge you priced; exclude upsizing beyond them; send an RFI when pressures are missing; and make sealed calculations part of the submittal, since A201 puts the engineer's seal on calculations as well as drawings. Where the documents never stated criteria, the A201 clause on who must specify them is where a change request starts.