Concrete Reinforcement Mesh: Designations, Spacing & Lap
Quick answer
For most ground slabs use A142 or A193 welded reinforcing fabric (BS 4483); use heavier A252 or A393 for structural slabs, rafts and walls. UK fabric is designated by cross-sectional steel area per metre, while US mesh is sized by bar spacing and area (e.g. 6x6 W1.4/W1.4).
By the WireMeshQA editorial team · Independent wire mesh reference
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.
Figure 1: Welded Mesh vs Loose Rebar for this application (indicative).
Figure summary: For concrete reinforcement, welded mesh sheets place fast with pre-set, consistent spacing that spreads crack control evenly across slabs and pavements, while loose rebar is tied by hand and suits beams and heavy structural work. Mesh saves labour on flat work; rebar handles concentrated loads.
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.
For a typical domestic ground slab, A142 or A193 welded reinforcing fabric to BS 4483 is common, with A193 giving a useful margin. Heavier loads, rafts and structural slabs need A252 or A393. The reinforcement, cover and position should be confirmed by a structural engineer for anything load-bearing.
What does A142 mesh mean?
A142 is a UK reinforcing fabric designation under BS 4483. The 'A' means a square mesh with equal bars both ways, and 142 is the cross-sectional area of main steel in mm² per metre width. It uses 6mm wire at 200mm spacing and is typically used for light ground slabs and blinding.
What is the equivalent of 6x6 W1.4 mesh in the UK?
US 6x6 W1.4xW1.4 welded wire reinforcement has 6-inch spacing each way with a 0.014 in² wire area, which is light fabric roughly comparable to UK A98–A142. Exact equivalence varies, so for structural work always match the cross-sectional steel area per metre to the engineer's specification rather than relying on a rough conversion.
How much should reinforcing mesh overlap?
A common rule of thumb is a lap of at least two full mesh squares plus 50mm so the reinforcement remains continuous, but laps must follow the project specification and code (such as BS EN 1992). Tie the sheets at the lap so they do not move during the pour, and keep the lap within areas of lower stress where possible.
Where should mesh sit in a concrete slab?
Reinforcing mesh should sit near the tension face, supported on chairs or spacers at the correct depth — often the lower third for a ground-bearing slab, or top and bottom for suspended slabs. Maintain proper cover (commonly around 40–50mm depending on exposure) so the steel is protected from corrosion.
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