Expanded metal mesh

What it is

Expanded metal is made by slitting a solid sheet or plate in staggered rows and stretching it, so that each slit opens into a diamond. Nothing is punched out and nothing is welded: the mesh is one continuous piece, lighter per square metre than the sheet it came from, with strands and bonds that stay connected even when a strand is cut. In its as-made, raised form the strands sit at an angle, giving a rigid, grippy surface; passed through a rolling mill it becomes flattened mesh with a smooth face.

Expanded mesh is used wherever light, air, drainage or visibility must pass but people, hands, tools or debris must not: walkways and platform decks in heavy patterns, machine guards, fencing and enclosures, ceilings, facades and sunscreens, balustrade infill, and plaster lath. It is a close relative of perforated panels and mesh flooring; for aluminium patterns see aluminium expanded mesh.

Types and options

Every pattern is described by the short way of the diamond (SWD), the long way of the diamond (LWD), the strand width and the thickness of the base metal. Together they set weight, open area, stiffness and how the mesh feels underfoot.

Mesh is supplied as standard sheets, cut to size, or framed: World Steel welds or bolts it into angle, flat bar or channel frames to make removable panels, guard sections, handrail infill panels and security screens.

Design and compliance

Expanded metal has no single product standard that every market uses. In the US, ASTM F1267 covers expanded steel mesh and the expanded metal manufacturers' standards published through NAAMM describe patterns and tolerances; elsewhere the mesh is specified by pattern, base material and finish, with the base sheet to its own standard. Walkway mesh is checked for the imposed load and span like any floor – AS 1657, EN ISO 14122-2 or OSHA 1910 Subpart D set the access rules, and the loads come from AS/NZS 1170.1, EN 1991-1-1 or ASCE 7. Mesh used as a machine guard must keep fingers and hands out of the danger zone: opening size and distance follow EN ISO 13857, AS 4024.1 or OSHA 1910.212.

Load and span values for a given pattern come from the mill's published data or a project calculation; World Steel does not publish generic load tables for mesh.

Fabrication and finishing at World Steel

Expanded mesh stock is produced on expanding presses by specialist mills and supplied by World Steel with the project package. In the World Steel plant in Vietnam we cut the mesh to size, trim the strands at the edges, and weld or bolt it into steel frames on jigs, using qualified procedures under ISO 3834-2 and our AS/NZS 5131 and EN 1090-2 systems. Framed mild steel panels are hot-dip galvanised after fabrication by qualified galvanisers or painted to the project specification; pre-galvanised or stainless mesh can be used where welding is limited and touch-up is acceptable.

Panels are marked to the layout drawing and packed flat on timber skids for export shipping, usually with the platforms or enclosures they belong to.

Selecting and specifying

• Name the use first – walkway, guard, screen or facade – because it decides the pattern weight and orientation.
• Give SWD, LWD, strand width, thickness, raised or flattened, and the base material, or ask us to propose a pattern for the duty.
• For walkways, state the imposed load, span and slip-resistance requirement; for guards, the reach distance to the hazard.
• State the direction of the LWD relative to the span or panel length, frame type and finish.