Cold-Formed Z and C Sections: Purlins and Girts

Cold-formed Z and C sections form the secondary framing of a pre-engineered building. Purlins span between rafters to support the roof sheeting, and girts span between columns to support the wall cladding. Together they collect loads from the envelope, deliver them to the primary frames and help stabilize the frame flanges.

The sections are roll-formed at room temperature from steel strip, usually galvanized or otherwise metallic coated. Z sections are commonly used for roof purlins because they can be nested and lapped over the supports, which makes them act as continuous beams and improves efficiency. C sections are often used for girts, door and window jambs, headers and framing around openings, where a flat back is convenient.

Depth, flange width and thickness are selected by the project engineer for the span, loads and bracing conditions, then checked against the cold-formed steel code for the project. Bridging or sag rods may be added to restrain the sections, and the sheeting itself often provides lateral support, depending on the roof system.

Holes for bolts and fixings are punched during roll-forming, so the sections arrive ready to bolt to the clips welded on the main frames. Each piece is marked and bundled for its location to simplify erection.

World Steel supplies Z and C sections as part of complete building packages and as separate supply for projects designed by others, in profiles and coatings suited to the code and environment specified for the project.

When ordering, state the profile, depth, thickness, coating, lengths, hole pattern and design code, or provide the loads and spans so that the sections can be selected by design. Lap and bracing details should be confirmed on the drawings.