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Materials & Specificationsaka: HVAC sheet metalaka: ductworkaka: flat metal

Sheet Metal

In Plain English

Thin flat metal panels used in construction for ductwork, flashing, roofing, and architectural elements.

Definition

Sheet metal in construction refers to thin, flat pieces of metal — typically steel, aluminum, or copper — used for HVAC ductwork, roofing, flashing, gutters, and architectural trim. HVAC sheet metal fabrication is a major specialty trade in commercial construction. Sheet metal thickness is measured in gauges, with lower numbers indicating thicker material.

Why It Matters in Bidding

Sheet metal is a major specialty bid package in commercial work, especially HVAC ductwork, so the GC relies on competitive sub quotes rather than self-performing the takeoff. Gauge requirements, SMACNA fabrication standards, and the split between roofing flashing and mechanical ductwork all affect scope coverage, and missing a flashing or trim line at bid time is a classic source of post-award scope disputes between the roofer, the HVAC sub, and the GC.

Example

A GC reviewing two sheet metal sub bids notices one excludes architectural coping and roof-edge flashing, so the estimator carries an allowance and flags the scope gap in the bid clarifications before award.

Related Terms

Galvanized SteelFlashingMetal StudSteel

Frequently Asked Questions

Ductwork is typically priced by the pound of fabricated metal plus installation labor, derived from a takeoff of duct sizes and lengths converted to weight by gauge. Flashing, gutters, and trim are priced by linear foot. Most GCs collect specialty sub quotes rather than self-perform, then reconcile scope across the trade packages.
Gauge indicates thickness, with lower numbers being thicker and heavier metal. Because ductwork is often priced by weight and heavier gauge costs more per square foot, confirming the specified gauge for each duct pressure class is essential, since assuming a lighter gauge can underbid the package significantly.
It depends on how the scope is bid. Roof-related flashing can fall under roofing or under the sheet metal package, so estimators must read both sub scope letters to ensure flashing, counter-flashing, gutters, and coping are carried exactly once. Overlaps inflate the bid; gaps create change orders.

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