What Reinforcing Mesh Is For
Welded reinforcing fabric (mesh sheets) distributes tensile stress and controls cracking in concrete slabs, rafts, walls and screeds. It is supplied as prefabricated sheets of deformed steel bars welded at each intersection, which is faster to place than loose rebar. The correct designation depends on the structural demand and is normally specified by an engineer.
UK Fabric Designations (BS 4483)
In the UK and much of the Commonwealth, standard fabric types are defined in BS 4483. The 'A' series is square mesh (equal bars both ways), the most common for slabs. The number is the cross-sectional area of main steel in mm² per metre width.
| Designation | Wire size (mm) | Pitch / spacing | Cross-sectional area (mm²/m) | Typical use |
|---|---|---|---|---|
| A142 | 6mm | 200 x 200mm | 142 | Light ground slabs, blinding |
| A193 | 7mm | 200 x 200mm | 193 | Domestic / general slabs |
| A252 | 8mm | 200 x 200mm | 252 | Heavier slabs, rafts |
| A393 | 10mm | 200 x 200mm | 393 | Structural slabs, walls, rafts |
US Mesh Sizing (WWR)
In the US, welded wire reinforcement (WWR) is written as spacing x spacing – wire size x wire size. For example, 6x6 W1.4xW1.4 means 6-inch bar spacing each way with W1.4 plain wire (0.014 in² cross-section). The older steel-wire-gauge style (e.g. 6x6 10/10) is being replaced by the W/D system.
| US designation | Spacing | Wire area (in²) | Rough UK equivalent |
|---|---|---|---|
| 6x6 W1.4xW1.4 | 6in x 6in | 0.014 | Near A98–A142 |
| 6x6 W2.9xW2.9 | 6in x 6in | 0.029 | Near A193 |
| 6x6 W4.0xW4.0 | 6in x 6in | 0.040 | Near A252 |
| 4x4 W4.0xW4.0 | 4in x 4in | 0.040 | Heavier slab |
Bar Spacing, Lap & Cover
Sheets must overlap so the reinforcement is continuous. As a common rule of thumb, structural laps are at least two full mesh squares plus 50mm, but always follow the project specification and code. Maintain correct concrete cover with spacers — too little cover risks corrosion, too much reduces effectiveness.
| Item | Common guidance | Notes |
|---|---|---|
| Minimum lap | 2 mesh squares + 50mm | Follow engineer's spec / BS EN 1992 |
| Cover (ground slab) | ~40–50mm | Depends on exposure class |
| Spacing chairs / spacers | Every ~600–1000mm | Keeps mesh at correct depth |
| Position in slab | Near the tension face | Often lower third for ground slabs |
Specifying & Ordering
- Always use the designation called up on the structural drawing — do not substitute a lighter fabric.
- Standard UK sheets are commonly 4.8m x 2.4m; allow for laps when calculating sheet count.
- Support mesh on chairs or spacers; never pull it up through wet concrete by hand.
- Tie sheets at laps so they do not shift during the pour.
- Estimate sheet and reinforcement weight with our weight calculator and read designations in our how to read mesh specs guide.