Raised (standard) expanded metal
Supplied as it leaves the press, with strands and bonds set at an angle to the sheet plane. Strongest for its weight and naturally slip-resistant. Used for walkways, guards, fencing and partitions.
Mesh specification guide
Aluminium Expanded Metal Mesh
Aluminium expanded metal is a one-piece mesh made by slitting and stretching aluminium sheet or coil into a pattern of diamond-shaped openings, with no material removed and no welds. It is lighter than the sheet it came from, rigid, slip-resistant in its raised form and does not rust. This guide explains how it is made and specified, which alloys to choose, how to calculate weight, and where it is used.
- Alloys
- 3003, 5052, 5005, 1100, 6061
- Types
- Raised · flattened · micro
- Thickness
- 0.05 – 6 mm feedstock
- Standard
- EMMA 557 (NAAMM)
What is aluminium expanded metal?
Expanded metal starts as solid sheet or coil. An expanding press cuts a row of short, staggered slits and, in the same stroke, pulls the metal forward so the slits open into diamonds. The strands and the bonds (the nodes where strands meet) remain one continuous piece of metal. Because nothing is punched out, almost all of the feedstock ends up in the finished mesh.
Compared with perforated sheet, expanded metal gives a larger open area for the weight, more stiffness from the angled strands, and natural grip when left in the raised condition. Compared with woven or welded wire mesh, it has no joints to loosen or break, and the strands cannot unravel when the mesh is cut. These qualities explain why the same basic product turns up in facade screens, walkways, machine guards, grease filters, plaster lath and electronic shielding.
Aluminium versions add corrosion resistance without galvanising, low weight (about one third that of steel mesh with the same pattern), high thermal and electrical conductivity and an excellent base for anodising and powder coating. Metline supplies aluminium coil and sheet for expanded metal production, and expanded aluminium mesh in sheets, coils and cut panels to buyers worldwide.
Expanded metal terminology: SWD, LWD, strand and bond
Expanded metal has its own vocabulary, standardised in North America by the Expanded Metal Manufacturers Association (EMMA, part of NAAMM) in its EMMA 557 standard. Understanding these terms avoids most ordering errors.
| Term | Meaning | Why it matters |
|---|---|---|
| SWD – short way of the design | Distance from the centre of one bond to the centre of the next across the short diagonal of the diamond | With strand size, controls weight and strength |
| LWD – long way of the design | Same measurement across the long diagonal | Usually about 2 to 2.5 times the SWD for standard patterns |
| SWO / LWO – short and long way of opening | The clear opening inside the diamond, measured inside the strands | Determines what passes through: air, light, particles, fingers |
| Strand width (SW) | Width of metal fed forward per stroke, which becomes the strand width | Wider strands give more weight, strength and less open area |
| Strand thickness (T) | Thickness of the strand, usually close to the base sheet thickness | Main driver of load capacity |
| Bond | The double-thickness node where two strands meet | Gives stiffness; in raised mesh the bonds tilt and create grip |
| Open area | Percentage of the surface that is open | Ventilation, light transmission, drainage and weight |
Patterns are often written as SWO × LWO × T × SW in millimetres, for example 3.2 × 5.0 × 1.5 × 0.7, or in North America by SWD and base gauge, for example "3/4 in, 0.050 in". Because suppliers use different conventions, always state which dimensions you are quoting, and whether they are nominal design dimensions or measured openings. EMMA 557 allows a tolerance of about ±10 % on weights and design dimensions for standard mesh, tighter for load-bearing grating.
Types of aluminium expanded metal
Flattened expanded metal
Raised mesh passed through a cold-rolling mill to flatten the strands into one plane. Smooth to touch, easier to paint and frame, slightly longer in the LWD direction and thinner overall. Used for facades, ceilings, shelving and decorative panels.
Expanded metal grating
Heavy-gauge mesh from thick plate, typically 3 – 6 mm, for platforms, catwalks and stair treads where loads must be carried between supports. Usually 5052 or 6061 alloy.
Micro expanded metal
Very fine mesh from foil and thin strip (about 0.05 – 0.3 mm) with openings below 1 – 2 mm. Used for filtration, battery current collectors, EMI shielding and lightning-strike protection layers in composite parts.
Architectural mesh
Large or decorative patterns, including hexagonal, scale and custom shapes, made for facades, sunscreens, ceilings and interior features. Often anodised or PVDF coated.
Expanded metal lath
Light diamond mesh used as a substrate for plaster, render and fireproofing; the open diamonds key the coating mechanically.
Which aluminium alloy for expanded metal?
The alloy must stretch without tearing at the bonds, yet give the finished mesh enough strength and the right surface for its finish. Non-heat-treatable alloys in quarter-hard to half-hard tempers are the usual choice.
| Alloy and temper | Typical tensile strength | Character | Best for |
|---|---|---|---|
| 1050 / 1100 (O, H14) | 90 – 125 MPa (H14) | Highest ductility, conductivity and corrosion resistance; low strength | Micro mesh, filters, lath, electrical shielding |
| 3003-H14 | About 150 MPa | The general-purpose expanded metal alloy: expands cleanly, moderate strength, good corrosion resistance | Guards, screens, grease filters, decorative panels |
| 5005-H34 | About 160 MPa | Similar strength to 3003 with a better, more uniform anodised appearance | Anodised facade and interior mesh |
| 5052-H32 | About 230 MPa | Higher strength and fatigue resistance; excellent in marine atmospheres | Walkways, grating, marine and coastal installations |
| 6061-T6 | About 310 MPa | Heat-treated; strongest option but less ductile, so patterns must be chosen with care | Heavy grating and structural mesh |
Typical values for the base sheet (Aluminum Association / ASM). Expanding cold-works the bonds, so the mesh behaves as a structure rather than a sheet; load tables from the mesh supplier, not sheet properties, should be used for design.
Base sheet and coil for expanded metal is usually ordered to ASTM B209 or EN 485 / EN 573-3. If the mesh will be anodised, specify an anodising-quality alloy such as 5005 and keep the whole project on material from one source, because the anodised tone varies with composition.
Patterns, sizes and how to calculate weight
Because the press feeds forward one strand width per stroke and each stroke produces half a diamond, the weight of expanded metal per square metre (measured flat on plan) can be estimated from the pattern alone:
| SWD (mm) | Strand width (mm) | Strand thickness (mm) | Approx. weight (kg/m²) |
|---|---|---|---|
| 3.2 | 0.7 | 1.5 | 1.77 |
| 6 | 0.8 | 0.8 | 0.58 |
| 10 | 1.2 | 1 | 0.65 |
| 12.7 | 1.5 | 1.5 | 0.96 |
| 19 | 2 | 1.6 | 0.91 |
| 25.4 | 2.5 | 2 | 1.06 |
| 25.4 | 3.2 | 3 | 2.04 |
| 32 | 4 | 4 | 2.70 |
| 50.8 | 4.7 | 4 | 2.00 |
Calculated from geometry at a density of 2.70 g/cm³. Actual weight varies with the expanding process and within the tolerance of the standard; flattening does not change weight per unit length of strand but changes overall dimensions slightly.
Typical supply range
- Base thickness
- About 0.05 – 0.3 mm for micro mesh; 0.5 – 6 mm for standard, architectural and grating mesh
- SWD
- About 1 mm for micro mesh up to 50 – 75 mm for large architectural and grating patterns
- Sheet sizes
- 1219 × 2438 mm (4 × 8 ft), 914 × 1829 mm (3 × 6 ft), 1000 × 2000 mm, and cut panels such as 610 × 1220 mm
- Coil
- Widths up to about 1500 mm, continuous lengths for roll-formed and filter products
- Edges
- Open (cut through the diamonds) or bonded (cut through the bonds); framed edges on request
- Finish
- Mill, anodised, powder coated, PVDF; colours to RAL
How aluminium expanded metal is made
- FeedstockCoil or sheet of the chosen alloy and temper is inspected for thickness, flatness and surface.
- Slit and expandThe expanding press feeds the sheet forward by one strand width per stroke while a stepped knife slits and stretches it, offsetting the knife each stroke to stagger the diamonds.
- Flatten (optional)Raised mesh is passed through a cold-rolling mill to produce flattened expanded metal with a smooth surface.
- Level and cutMesh is levelled and sheared to sheet or panel size, or recoiled.
- FinishPretreatment and anodising, powder coating or PVDF coating as specified.
- Inspect and packPattern dimensions, strand size, weight per area, flatness and finish checked; sheets interleaved and packed on pallets or in cases.
Pattern choice affects strength in each direction. Expanded metal is stiffer along the LWD than across it, so in walkways and spans the LWD normally runs between the supports. State the LWD direction on the drawing for any load-bearing or framed panel.
Expanding also changes the dimensions of the sheet. A given width of feedstock produces mesh of roughly the same width in the LWD direction, but the length grows several times in the SWD direction, depending on the ratio of SWD to strand width. This is why expanded mesh covers a much larger area than the sheet it was made from, and why ordering by finished area rather than by feedstock weight is normal practice. Flattening then adds a few per cent to the LWD length and reduces the overall thickness.
Fabrication and finishing of expanded aluminium
Cutting
Shearing, laser, waterjet and plasma all work. Cuts through the bonds leave a stronger, neater edge than cuts through the strands.
Framing and edging
Edges are often captured in aluminium angle, U-channel or tube frames, or folded edging strips, which stiffen the panel and remove sharp ends.
Bending and forming
Flattened mesh in soft tempers can be folded and curved; raised mesh can be rolled into curves for facades and guards.
Welding
TIG or MIG with 4043 or 5356 filler joins mesh to frames; low heat input avoids burning through thin strands.
Anodising
Gives a hard, durable metallic finish. Use 5005 or anodising-quality 3003 for consistent colour on visible facades.
Powder coating and PVDF
Powder is economical in any RAL colour; PVDF gives the best colour retention for coastal and high-UV facades. Mesh is best coated after cutting to protect edges.
Where aluminium expanded metal is used
| Sector | Typical product | What the mesh does |
|---|---|---|
| Architecture and facades | Flattened or architectural mesh, anodised or PVDF | Sun screening, visual screening, rainscreen and car-park facades |
| Interiors | Flattened decorative mesh | Ceilings, partitions, stair infill, retail displays |
| Industrial access | 5052 or 6061 raised mesh and grating | Walkways, platforms and stair treads that drain and grip |
| Machine and equipment guarding | 3003 raised mesh in frames | Visible, ventilated guards and enclosures |
| HVAC and kitchens | 1100 or 3003 mesh | Grease filters, air filter supports, vent covers |
| Electronics and batteries | Micro expanded foil | EMI shielding, current collectors, heat spreading |
| Aerospace composites | Micro expanded aluminium foil | Lightning-strike protection layers in composite skins |
| Marine and transport | 5052 mesh | Deck walkways, trailer floors, ventilation grilles |
| Security and fencing | Raised mesh panels | Perimeter fencing and partitions that resist climbing and cutting |
Aluminium is not always the right choice. For heavy vehicular loads or high-security barriers, steel expanded metal or bar grating carries more load at lower cost; for very fine filtration, woven wire mesh gives more precise openings. Aluminium wins where weight, corrosion resistance and appearance matter.
Selection tips and common mistakes
- Confirm whether quoted sizes are design dimensions (SWD/LWD) or clear openings (SWO/LWO); mixing them changes the product completely
- Run the LWD between supports for walkway and spanning panels, and check deflection with the supplier’s load tables
- Choose raised mesh for grip and strength, flattened mesh for smooth surfaces, painting and framing
- Use 5052 for coastal or marine sites and 5005 where anodised appearance must be consistent
- Isolate aluminium mesh from steel frames and fixings with stainless steel fasteners or isolating washers to avoid galvanic corrosion
- For facades, check fire and wind-load requirements of the local building code for the whole assembly, not just the mesh
References and standards
- NAAMM EMMA 557 – Standards for Expanded Metal
- ASTM B209 – Aluminum and Aluminum-Alloy Sheet and Plate
- EN 573-3 – Chemical composition and form of wrought products
- The Aluminum Association – Aluminum Standards and Data
Aluminium (aluminum) expanded metal: frequently asked questions
What is the difference between raised and flattened expanded metal?
Raised expanded metal is supplied as expanded, with the strands angled out of plane; it is stronger for its weight and slip-resistant. Flattened expanded metal is cold-rolled after expanding so the surface is smooth and flat, which suits painting, framing and decorative use.
Which aluminium alloy is best for expanded metal?
3003-H14 is the general-purpose choice. Use 5052-H32 for higher strength and marine environments, 5005 for consistent anodised facades, 1100 or 1050 for micro mesh and filters, and 6061-T6 for heavy grating.
How do I calculate the weight of aluminium expanded metal?
Multiply 2 × strand width × strand thickness × 2.70 and divide by the SWD, all in millimetres, to get kg/m². For example, a 12.7 mm SWD pattern with 1.5 × 1.5 mm strands weighs about 0.96 kg/m².
Is expanded metal stronger than perforated sheet?
For the same weight and open area, expanded metal is usually stiffer, because the angled strands and bonds act like a truss and no material is removed. Perforated sheet gives a flatter, more uniform surface and more precise hole sizes.
Can expanded aluminum mesh be anodised or powder coated?
Yes. Both finishes are common. Anodising suits 5005 and anodising-quality 3003; powder coating and PVDF work on all common alloys and are best applied after cutting so the edges are protected.
Does expanded metal waste material?
Very little. The sheet is slit and stretched, not punched, so nearly all the feedstock becomes mesh, and the finished mesh covers a larger area than the original sheet.
Need expanded aluminium mesh?
Tell us the pattern, alloy, size, finish and quantity. We will confirm options, documents and a delivered price anywhere in the world.
