Applies to contractors engaged in the installation or repair of sheet metal work in building construction, not covered by another classification (N.O.C.). Work contemplated by this classification applies to interior and exterior sheet metal work for residential or commercial buildings; this includes sheet metal work on wood frame, pole buildings, and nonwood frame buildings. This classification includes the installation of metal siding, gutters and downspouts, nonstructural sheet metal patio covers/carports, metal industrial shelving, stainless steel counter tops, and interior wall panels (such as the back splash behind stoves or sinks). Contractors who operate a sheet metal fabrication shop or prefabricate the gutters, downspouts and posts in a shop away from the construction site are to be assigned classification 3404 for the shop operations. When a contractor's business is assigned classification 3404 for shop operations then classification 5206 "Permanent yard or shop" is no longer applicable to the contractor's business for the storage of materials or repair to equipment.

This classification excludes sheet metal work as part of heating ventilation and air conditioning systems installation which is to be reported separately in classification 0307; the installation of aluminum or sheet metal as part of roof work which is to be reported separately in classification 0507; the installation of light weight sheet metal tool sheds which is to be reported separately in classification 0516; and the installation of commercial metal carports and service station canopies which is to be reported separately in classification 0518.