Welded wire mesh in Canada is sized by wire spacing and wire area, written as a style such as 152x152 MW18.7xMW18.7 (the metric name for the old "6x6 6/6"). The common construction styles have 152 mm (6 in) spacing each way, with wire from MW9.1 (10 gauge) up to MW25.7 (4 gauge). Mesh comes in flat sheets, where 2.44 m (8 ft) is the standard width, and in rolls, commonly 30 m or 60 m long.
How a mesh size is written
A mesh "style" tells you four things, in this order: the spacing of the longitudinal wires, the spacing of the transverse wires, the size of the longitudinal wires and the size of the transverse wires.
Take 102x152 MW18.7xMW25.8 as an example:
- Longitudinal wires every 102 mm.
- Transverse wires every 152 mm.
- Longitudinal wires of 18.7 mm² area.
- Transverse wires of 25.8 mm² area.
Most construction mesh is square, with the same spacing and wire both ways, so you will usually see styles like 152x152 MW13.3xMW13.3.
The prefix tells you the wire type:
- MW: plain (smooth) wire, metric.
- MD: deformed wire, metric.
- W and D: the imperial versions, where the number is the wire area in hundredths of a square inch. W2.9 is 0.029 in².
The number is area, not diameter. MW18.7 wire has 18.7 mm² of area, which works out to a diameter of about 4.9 mm. This trips people up because rebar names (10M, 15M) roughly track diameter.
You will still hear the old gauge names on site: "6x6 10/10" or "6x6 6/6". The first pair is the spacing in inches; the second pair is the wire gauge each way. Gauge numbers run backwards, so 6 gauge is heavier than 10 gauge. Our post on wire mesh vs rebar for slabs explains how to compare a mesh designation with a rebar grid.
Common welded wire mesh sizes
These are standard construction mesh styles listed in the Reinforcing Steel Institute of Canada (RSIC) Manual of Standard Practice, with steel area per metre of width in each direction and the approximate mass of the mesh.
| Metric style | Imperial / gauge name | Steel area each way (mm² per m) | Mass (kg/m²) |
|---|---|---|---|
| 152x152 MW9.1xMW9.1 | 6x6 10/10 | 59.9 | 1.02 |
| 152x152 MW11.1xMW11.1 | 6x6 9/9 | 74.3 | 1.22 |
| 152x152 MW13.3xMW13.3 | 6x6 8/8 | 88.7 | 1.46 |
| 152x152 MW18.7xMW18.7 | 6x6 6/6 | 124.5 | 2.05 |
| 152x152 MW25.7xMW25.7 | 6x6 4/4 | 171.5 | 2.83 |
| 102x102 MW18.7xMW18.7 | 4x4 6/6 | 186.8 | 3.02 |
| 102x102 MW25.7xMW25.7 | 4x4 4/4 | 257.2 | 4.14 |
Heavier styles exist too, including 152 mm mesh with larger wires, 305 mm (12 in) spacing styles with heavy wire, and deformed-wire styles for structural use. Calculated values can differ slightly between sources because 152 mm and 6 in are not exactly the same spacing.
For comparison, a grid of 10M rebar at 300 mm each way gives about 333 mm² per metre, and 10M at 400 mm gives 250 mm² per metre. Even the heavier common mesh styles carry less steel than a light rebar grid. That does not make one better than the other; they do different jobs, and the choice belongs to the designer. Our slab-on-grade rebar post covers when a slab needs engineered reinforcement.
Wire gauge to metric conversion
If a drawing, an old spec or a store label uses gauge or W numbers, this table translates them. Values are from the RSIC wire size tables.
| Old gauge | Imperial wire size | Metric wire size | Approx. wire diameter |
|---|---|---|---|
| 10 gauge | W1.4 | MW9.1 | 3.4 mm |
| 9 gauge | W1.7 | MW11.1 | 3.8 mm |
| 8 gauge | W2.1 | MW13.3 | 4.1 mm |
| 7 gauge | W2.5 | MW15.9 | 4.5 mm |
| 6 gauge | W2.9 | MW18.7 | 4.9 mm |
| 4 gauge | W4.0 | MW25.7 to MW25.8 | 5.7 mm |
Some tables round the metric areas slightly differently (MW9.1 vs MW9.2, for example). They refer to the same wire. If a supplier offers a style that is close to but not exactly what is specified, check the steel area per metre against the drawings and ask the designer before accepting it.
Sheet and roll sizes
Mesh is supplied two ways, and the choice affects handling, laps and waste.
Sheets. Flat sheets are furnished to order. According to the RSIC manual, 2.44 m (8 ft) wide sheets are the standard width, with other sizes available on request, and the maximum sheet size is often set by truck or rail limits rather than by the mesh machine. Sheet lengths should be a multiple of the cross-wire spacing. The RSIC style chart lists sheet sizes such as 4x8 ft, 5x10 ft, 8x12 ft and 8x20 ft, depending on the style; lighter styles come in the smaller sheets and heavier styles in 8 ft wide sheets.
Rolls. Rolls can be made to almost any length within each producer's limits, but 30 m and 60 m are the commonly accepted standard lengths. Rolls are convenient for light mesh over large areas, but they want to curl, which makes it harder to keep the mesh flat and at the right height. The RSIC manual limits:
- Mesh with longitudinal wires larger than MW50 is always furnished as flat sheets.
- Where the mesh must lie substantially flat in the work, rolls should be limited to styles with longitudinal wires no larger than MW35.
Finish. Mesh is supplied bright (uncoated) unless galvanized is specified. Some styles are available galvanized; check availability early, because not every style is stocked that way.
Availability varies. Wire sizes, spacings and sheet sizes depend on each producer's equipment, so RSIC advises specifiers to check with a local supplier that a style can be readily produced and shipped. Retail stores usually carry only a few light styles in small sheets.
Standards and grades
Welded wire reinforcement in Canada and the US is specified to ASTM A1064/A1064M, which covers carbon-steel wire and welded wire reinforcement, plain and deformed, for concrete. The RSIC manual notes that mesh is available in higher-strength grades than ordinary rebar, so an engineer converting a rebar design to deformed mesh may be able to use less steel area. That conversion is a design calculation, not something to do on site.
Design rules for development and splices of welded wire fabric are in CSA A23.3, and placement and cover are covered by CSA A23.1 and the project specification. If your slab is designed by an engineer, the mesh style, laps and position come from the drawings.
Ordering the right amount
A few points from standard practice that help when ordering:
- Add for laps. Sheets and rolls overlap at their edges, so you need more mesh than the slab area. RSIC suggests allowing at least 10% extra for rolls and 15% for sheets, or whatever the specification's lap requirements work out to.
- Know your lap rule. Laps for mesh depend on the wire type and on how many cross wires fall within the overlap. Follow the specification or ask the designer; do not guess.
- Plan the supports. Mesh needs chairs or blocks to sit at the right height. Mesh laid on the ground and "pulled up" during the pour is not acceptable practice, and it usually ends up at the bottom of the slab. Our post on where rebar should sit in a slab explains why position matters.
- Count the edge overhangs. Transverse wires normally stick out past the outside longitudinal wire by up to about 25 mm on each side. Account for this where sheets meet walls or forms.
When a slab calls for rebar instead
Mesh is mostly used as light temperature and shrinkage reinforcement in slabs. Where a slab carries heavier loads, spans soft ground, or the drawings call for a specific steel area, the reinforcement is often a rebar mat instead. Our post on rebar mesh pricing covers what drives the cost of each, and wire mesh vs rebar for a garage floor works through a common residential case.
If your drawings call for a rebar mat, we can detail it, cut the bars and deliver them tagged and ready to place. Send us your drawings for a free take-off and quote. We don't supply welded wire mesh itself. See our rebar products for the bar sizes and fabricated shapes we supply.
Frequently asked questions
What size does rebar mesh come in?
Construction mesh in Canada is most often 152 x 152 mm (6 x 6 in) spacing with wire from MW9.1 to MW25.7. It comes in flat sheets, with 2.44 m (8 ft) the standard width, and in rolls, commonly 30 m or 60 m long. Exact sheet and roll sizes vary by producer and supplier.
What does 6x6 10/10 wire mesh mean?
Wires spaced 6 in (152 mm) apart in both directions, each wire 10 gauge. In current metric terms that is 152x152 MW9.1xMW9.1, where 9.1 is the wire's cross-sectional area in mm².
What gauge is 152x152 MW18.7 mesh?
MW18.7 is the metric equivalent of W2.9, which is the old 6 gauge wire. So 152x152 MW18.7xMW18.7 is the same mesh as 6x6 W2.9xW2.9, often called 6x6 6/6.
Is the MW number the wire diameter?
No. The number after MW (plain wire) or MD (deformed wire) is the cross-sectional area in square millimetres. MW18.7 wire is about 4.9 mm in diameter.
What standard covers welded wire mesh in Canada?
Welded wire reinforcement used in Canada and the US is specified to ASTM A1064/A1064M, which covers carbon steel wire and welded wire reinforcement, plain and deformed, for concrete.
