Mesh basics
What is welded wire mesh?
Welded wire mesh is a prefabricated grid of cold-drawn steel wires joined by electrical resistance welding at each intersection. Placed in concrete, it holds shrinkage cracks tight and preserves load transfer across joints. In Canada and the US, standards designate it as welded wire reinforcement (WWR), previously called welded wire fabric (WWF) or remesh.
One product, many names
| Name | Who uses it |
|---|---|
| Welded wire reinforcement (WWR) | Current standard term in ASTM A1064, CSA G30.5, and modern engineering drawings |
| Welded wire fabric (WWF) | Older drawings, legacy specifications, and trade references; still widely used |
| Remesh, concrete mesh, slab mesh | Job sites, flatwork crews, and building supply distributors |
| Weld mesh | Common in Australia, the UK, and international trade; often includes fencing mesh |
ASTM A1064 and the Wire Reinforcement Institute adopted "welded wire reinforcement" in place of "welded wire fabric" because it more accurately describes the material's structural performance in reinforced concrete (ASTM A1064).
Be careful with the broad search term "wire mesh" on its own. In industrial and hardware catalogs, it often refers to light woven wire cloth, hardware cloth, or boundary fencing, none of which meet concrete reinforcement specifications.
How it is manufactured and specified
Reinforcing mesh starts as hot-rolled steel rod that is cold-drawn through precision dies to its final wire diameter. Cold drawing increases the steel's tensile yield strength from approximately 275 MPa (40 ksi) up to 450 to 550 MPa (65 to 80 ksi).
The longitudinal and transverse wires are positioned automatically in an orthogonal grid and joined by electrical resistance fusion welding. No welding wire, flux, or filler metal is added. Heat is generated solely by electrical resistance at the wire contact points under mechanical pressure, creating a clean metallurgical weld.
ASTM A1064 unified four historical ASTM standards into a single specification:
- ASTM A82: Plain cold-drawn steel wire
- ASTM A185: Plain welded wire fabric
- ASTM A496: Deformed cold-worked steel wire
- ASTM A497: Deformed welded wire fabric
In Canada, the corresponding material specification is CSA G30.5 (Welded steel wire fabric for concrete reinforcement), referenced within CSA A23.1 and CSA A23.3. Under ASTM A1064, plain wire requires a minimum yield strength of 450 MPa (65 ksi), while deformed wire requires 485 MPa (70 ksi). Modern design standards, including ACI 318-25 Table 20.2.2.4(a), permit yield strengths up to 550 MPa (80 ksi) for welded wire reinforcement.
How cross wires anchor in concrete
Unlike hot-rolled rebar, which relies primarily on surface deformations along the bar shaft to bond with concrete, plain welded wire mesh anchors through its welded intersections.
Decades of bond testing showed that the welded cross wires act as positive mechanical anchor lugs bearing directly against the surrounding concrete matrix (Becker, 1949). To guarantee this mechanical anchorage, ASTM A1064 Section 7.4 mandates a strict weld shear test: the weld between the wires must resist a minimum shear force of 241 MPa (35,000 psi) multiplied by the area of the larger wire whenever the smaller wire's area is at least 40% of the larger wire.
What it does in concrete
Concrete has high compressive strength but relatively low tensile capacity, roughly 10% of its compressive strength. As the concrete cures, loses moisture, and cools, it shrinks. When subgrade friction or structural boundaries restrain this shrinkage, tensile stress accumulates until the concrete cracks (Weiss, Yang & Shah, 1998).
Steel reinforcement cannot eliminate internal shrinkage forces or stop cracks from initiating. Mesh does not prevent cracking. What it does is bridge cracks as they form, distributing stress and keeping crack widths tight (under 0.5 mm or 0.02 in). Narrow cracks maintain aggregate interlock, prevent vertical offset between adjacent slab sections, and keep water, dirt, and de-icing chemicals out of the joint.
Where welded wire reinforcement is used
- Slabs-on-ground: Driveways, garage pads, basements, commercial warehouse floors, exterior aprons.
- Composite steel deck: Structural concrete slabs on corrugated metal decking in multi-storey buildings.
- Precast concrete: Utility boxes, drainage pipes, retaining wall panels, barrier rails.
- Underground support: Welded wire mesh screening for mine openings, tunnel linings, and civil rock stabilization.
- Structural walls and foundations: Shear reinforcement, tilt-up wall panels, and continuous strip footings.
Mesh compared with alternatives
Builders typically choose between welded wire mesh, tied rebar mats, and synthetic fibres:
- Wire mesh sheets: Rapid placement. Field studies show welded wire sheets reduce placement labour by 30% to 50% compared with placing and tying individual rebar grids (Bernold & Chang, 1992).
- Rebar: Thicker cross-sections and higher steel areas for heavy concentrated loads or structural members. Higher on-site tying labour.
- Synthetic fibres: Mixed into the concrete batch. Microfibres help with early plastic shrinkage during the first 6 hours; macrofibres provide post-crack toughness, but do not provide the continuous structural yield strength of steel mesh.
For detailed comparisons, see wire mesh vs rebar and fibre vs wire mesh.
How to read a mesh designation
A standard designation such as 6x6-W2.9xW2.9 communicates:
- 6x6: Wire spacing of 6 in (152 mm) between longitudinal wires and 6 in (152 mm) between transverse wires.
- W2.9xW2.9: Wire cross-sectional area of 0.029 in² (18.7 mm²) in both directions, where "W" denotes smooth plain wire. This corresponds to 6 gauge steel wire.
See the complete welded wire mesh sizes chart for gauge, W-number, and metric conversions.
- ASTM A1064/A1064M, Standard specification for carbon-steel wire and welded wire reinforcement for concrete. Link
- CSA G30.5, Welded steel wire fabric for concrete reinforcement. CSA Group.
- Wire Reinforcement Institute (2026), Manual of Standard Practice: Structural Welded Wire Reinforcement (WWR-500-R-26). Link
- Wire Reinforcement Institute, Tech Fact TF 101-R-14: The Architecture of ASTM A1064. Link
- Becker (1949), Transverse anchorage and adhesive bond in welded wire reinforcement. Link
- Bernold & Chang (1992), Potential gains through welded-wire fabric reinforcement, J. Construction Engineering and Management. Link
- Weiss, Yang & Shah (1998), Shrinkage cracking of restrained concrete slabs, J. Engineering Mechanics. Link
Questions
Is welded wire mesh good for concrete?
Yes. Held in the upper third of the slab, it keeps shrinkage cracks tight, preserves aggregate interlock, and stops slab edges from shifting out of level.
What are the disadvantages of welded wire mesh?
It does not stop concrete from cracking initially, and thin wire can sag to the bottom of the pour if not held on chairs at 600 to 900 mm (24 to 36 in) spacings.
Does wire mesh make concrete stronger?
It does not increase the compressive strength of the concrete mix itself, but it adds tensile capacity and holds fractured sections together once shrinkage cracks occur.
What is the difference between WWF and WWR?
They are the same product. ASTM A1064 and CSA standards adopted "welded wire reinforcement" (WWR) to replace "welded wire fabric" (WWF) because it better describes its structural role.