Aluminium Z Bar & Zed Section

What is an aluminium Z bar?

A Z bar has a web and two flanges, one turned each way. That simple geometry lets one flange fix to a wall or frame while the other sits a fixed distance away to carry a panel, a sheet edge or a second structure. It is the standard way to create an offset or a step in a single piece of metal.

In Britain and much of the Commonwealth the section is called a zed; in North America it is usually a Z bar or Z channel. The names describe the same family, which ranges from 10 mm trim profiles that hide a joint to heavy structural sections that support rainscreen cladding.

Two everyday uses explain most demand. In cladding and roofing, rows of Z bars fixed to a wall create a ventilated cavity and a flat plane on which panels are mounted; the depth of the web sets the cavity and insulation thickness. In panel hanging, two interlocking Z profiles (one on the wall, one on the back of a panel, mirror, sign or cabinet) act as a cleat: the panel is lifted on, self-locates and can be lifted off again.

Aluminium suits these jobs because it does not rust, is light enough to handle at height, extrudes into exact shapes with integral grooves or knurled faces, and can be anodised or powder coated to match the visible finish.

Alloys and tempers for Z sections

Single values are maximums. Others 0.05 % each, 0.15 % total; aluminium is the remainder. Limits follow the Aluminum Association registrations and EN 573-3.

For 2024 the main alloying addition is copper (3.8 – 4.9 %) with magnesium (1.2 – 1.8 %) and manganese (0.30 – 0.9 %); that copper is what gives its strength and also its lower corrosion resistance compared with the 6xxx alloys.

Strength of Z bars by alloy and temper

Specified minimums for extruded profiles; thicker walls fall into different bands. Typical values run 10 – 20 % higher (6061-T6 typically 310 MPa tensile, 276 MPa yield). Design to the minimums and the actual figures on the mill certificate.

2024-T3511 extrusions are specified to considerably higher minimums (tensile around 400 MPa or more, depending on thickness) under aerospace specifications such as AMS-QQ-A-200/3; they are ordered against that specification rather than general commercial standards.

All of these alloys share a density of about 2.70 – 2.78 g/cm³ and an elastic modulus near 69 – 73 GPa. A Z bar therefore weighs about one third of a steel zed of the same shape and is about three times more flexible, which matters for cladding rails spanning between brackets.

How a Z section carries load

A Z section is point-symmetric: its shear centre and centroid coincide, so, unlike a channel, it does not twist when loaded through the centre of the web. Its principal axes, however, are inclined to the web. Load it vertically and it bends partly sideways as well as down. In cladding and purlin systems this is controlled by the panels or sheeting fixed to the flanges, which restrain the sideways movement.

For a free-standing member with no such restraint, a channel, angle pair or box section is usually more predictable. Where Z bars are used as rails, check deflection with the section properties about the principal axes, or rely on the supplier's tested span tables for proprietary cladding systems.

Z bar and zed section sizes and weights

Weight per metre equals area × density. For a square-cornered zed, area = t × (F1 + F2 + H − 2t), and weight in kg/m = area in mm² × 0.0027. The table gives figures for common UK, metric and inch-derived sizes.

Calculated for 6063/6061 at 2.70 g/cm³ without corner radii. Inch sizes are shown converted (25.4 mm = 1 in).

Finishes for Z sections

Most cladding and hanging zeds are hidden and can be left mill finish. Visible trims and display profiles are usually anodised (clear, satin, bronze or black) or powder coated. For exterior anodising, specify film thickness, for example AAMA 611 Class I (≥ 18 µm) or Qualanod class 20 or 25; for military or aerospace parts, anodising to MIL-A-8625 (Type II sulphuric or Type III hard) is common. Powder coatings are typically 60 – 80 µm and can be specified to Qualicoat or AAMA 2604 / 2605.

• Mill finish: economical; for concealed rails and parts finished after fabrication
• Clear or satin anodised: durable, metallic look for trims and shop fittings
• Colour anodised: bronze, black or champagne to match window and façade systems
• Powder coated or painted: any RAL colour for signs, cabinets and panels
• Brushed: satin texture for furniture and retail displays

Processing, tolerances and inspection

Where aluminium Z bars are used

• Façades and roofing: sub-frames for rainscreen panels, ACP and fibre-cement boards, and spacers over insulation
• Interiors: hanging cleats for wall panels, mirrors, artwork, headboards and acoustic panels
• Shop fitting and displays: slatwall, shelf supports, poster rails and signage frames
• Cabinets and enclosures: door stops, panel stiffeners and frame members
• Transport: stiffeners on truck and trailer side walls, caravan body framing
• Aerospace: fuselage and wing stringers and frame members, typically in 2024 or 7075
• Doors and windows: rebate and weather-stop profiles, thresholds and step trims

Related profiles and guides

How to order Z bars from Metline

1. Describe the sectionFlange, web and wall dimensions, corner type and a sketch or drawing; or a sample to match.
2. Choose material and finishAlloy, temper, finish and any specification (ASTM B221, EN 755, aerospace AMS).
3. QuoteWe confirm die availability, tolerances, processing, certification and EXW, FOB, CIF or DAP terms.
4. Produce and inspectExtrusion, cutting, drilling and finishing, followed by dimensional and surface inspection.
5. ShipFilm-wrapped bundles or crates with EN 10204 3.1 certificate and packing list, by sea or air.

Aluminium Z bar and zed section (aluminum Z channel): FAQs