Z-Profiles and Z Purlins — Roll-Formed to Drawing

A Z-profile is an open section cold-formed from steel coil on a roll-forming line: the strip passes through successive roll stations until it has a web, two flanges pointing in opposite directions and a lip (edge stiffener) at each flange tip. The section is point-symmetric, and because its flanges face opposite ways, two Z-sections of the same size can nest inside each other. That is why Z-profiles are used above all as roof purlins (Z purlins) and wall girts in steel buildings, lapped over the supports along long runs.

In solar plants the same section is the purlin that carries the modules; that use is covered on our Y Solar solar purlins and rails page. Roof and wall purlins in C, Z and sigma sections are covered together on our purlin manufacturer page.

Because a Z-section's flanges face opposite ways, the end of one purlin slides inside the end of the next so that the two nest over a support (rafter, beam or column) and are bolted together. Across the lap the wall thickness is doubled, exactly where the purlin carries its largest moment, at the support. Instead of a string of separate spans, the run becomes a continuous beam over the supports.

In a continuous beam the mid-span moment and deflection are lower than in a single-span (simply supported) beam of the same span, so the same load can be carried by a lighter section or a thinner gauge. Lap length and the number and layout of bolts come from the project's structural calculation; we punch the lap holes in the same pass as the forming. In many purlin systems one flange is made slightly wider than the other so the sections nest easily; we roll the flange sizes on your drawing.

An equal-flange Z and a C of the same h × b × c × t have the same developed width and the same weight per metre; the difference is in how the section behaves. A Z is point-symmetric, so its shear centre coincides with its centroid instead of lying outside the web as in a C, and it is less prone to twisting under load. On the other hand a Z's principal axes are inclined to the web: under vertical load the purlin also tends to deflect sideways. That movement is restrained by the roof or wall cladding and, where needed, by sag rods.

For long multi-span roof and wall runs the Z purlin is the usual choice, because it can be lapped. A C-profile is the simple choice for single spans, around door and window openings and for short members, and many buildings use both. Where more bending capacity is needed at the same gauge, the stepped web of a sigma profile is the next option.

Web depth (h) sets the purlin's bending capacity about its major axis, flange width (b) the seat for the cladding and the lap as well as minor-axis stiffness, the lip (c) the flange's buckling resistance, and thickness (t) its load capacity. We roll Z-profiles from 1.0 mm to 6.0 mm thick, so 5 and 6 mm for heavily loaded purlins are within the range. Steel grade is a design lever too: with S420GD or S450GD instead of S350GD the same load is carried at a thinner gauge, lowering tonnage.

Z purlins are designed to EN 1993-1-3, where local and distortional buckling mean effective rather than gross section properties are used, and the inclined principal axes of the Z and the lateral restraint from the cladding enter the calculation. The project's structural calculation sets the final section, the lap length and the sag-rod layout. We support projects from the start with section optimisation and material and coating choice, so you do not pay for a purlin heavier than it needs to be.

The weight per metre of a cold-formed Z-profile comes from its centre-line developed width: developed width (mm) × thickness (mm) × 7.85 ÷ 1000 = kg/m. The bend radii shorten the developed width slightly; the table above accounts for that and shows equal-flange example sections. For a Z with unequal flanges, use the average of the two flange widths in the same calculation.

For example a 200×70×20 mm Z-profile in 2.5 mm weighs about 7.13 kg/m; with the same developed width, a C-profile of the same size also comes to about 7.13 kg/m. For your own size use our steel weight calculator or send us your drawing.

No. We form Z-profiles from pre-coated coil — Zn-Al-Mg (ZM120–ZM430) or galvanized (Z275–Z600) — so the profile leaves the line coated and needs no post-galvanizing bath. Zn-Al-Mg self-heals at sheared and punched edges and lasts longer than galvanizing at the same coating mass, which matters on purlins full of lap, connection and sag-rod holes. See our Zn-Al-Mg vs galvanized guide.

Z-profiles that will be painted or welded into a fabrication are also rolled from black steel. Where the specification calls for hot-dip galvanizing, we supply that too.

Decoiling and levelling, roll forming, in-line punching and flying cut-off to length all happen on one line. Lap and connection holes, sag-rod holes and slots are punched in the same pass as the forming, so hole positions are identical across thousands of parts and the holes of two lapped purlins line up on site.

Sections with no axis of symmetry, such as the Z, tend to twist and camber during forming; we compensate for that in the flower pattern (the forming sequence) and the straightening stands. Because we design and make the tooling and rolls in-house, a Z-section to your own drawing is taken from first article to series production by the same team. Design rules are covered in our guide to custom roll-formed profiles.

Profiles are packed by section and length, strapped with steel banding and labelled; we prepare the loading plan around the profile length. We ship across Türkiye and to Europe, the Middle East and North America by truck or container.

EN 10204 3.1 mill certificates and certificates of origin are provided on request; delivery terms (EXW, FOB or CIF) and the lead time are agreed at quotation. Production runs under an ISO 9001 quality management system.