Reinforcement
Mesh sheets for an area, with laps
- where
- sheets along the length
- length of area to reinforce (m)
- lap between sheets (mm)
- sheet length (m)
- sheets across the width
- width of area to reinforce (m)
- sheet width (m)
- total sheets
- total mass of mesh (kg)
- mesh mass (kg/m²): A142 2.22, A193 3.02, A252 3.95, A393 6.16
Explain this equation
Works out how many sheets of fabric mesh cover an area with laps, and their total weight.
Each sheet after the first only adds its length less the lap, because it overlaps the previous one. So the length to cover, less one lap, is divided by the sheet length less one lap, then rounded up; the same across the width. At least one sheet is always needed each way. The weight is sheets times sheet area times the mesh's mass per square metre.
The same laps arithmetic as underlay or roofing felt.
Sense check: a 10 × 5 m slab with 4.8 × 2.4 m sheets and 350 mm laps needs 3 × 3 = 9 sheets; in A193 that is about 313 kg.
Watch out: laps should be as specified by the designer (often 300 to 400 mm for A-mesh). Use chairs to keep the mesh at the right cover.
Works out how many standard mesh sheets cover a rectangular slab with laps at the joints, and their total weight.
Enter your values to see the result.
Good to know
BS 4483 A-meshes are square meshes at 200 mm centres: A142 (6 mm wires) 2.22 kg/m², A193 (7 mm) 3.02, A252 (8 mm) 3.95 and A393 (10 mm) 6.16 kg/m². The standard sheet is 4.8 × 2.4 m (11.52 m²); some merchants stock 3.6 × 2.0 m. Enter the area the mesh covers, which is the slab size less the edge cover at each side. Lap length comes from the design; a merchant minimum is 350 mm, and Eurocode 2 gives at least 200 mm and 15φ.
Common mistake
Dividing the slab area by 11.52 m², which ignores the laps and the part-sheets at the edges and leaves you short.
Limits
Rectangular areas with sheets laid all in one direction. The total mass counts full sheets bought, including offcuts. Lap length for structural slabs must be set by the designer.
Sources
- BS 4483:2005 Steel fabric for the reinforcement of concrete
- CR Steel, Shape code / steel calculator sheet (BS 8666 bar masses; BS 4483 meshes A142 2.22, A193 3.02, A252 3.95, A393 6.16 kg/m²)
- Reinforcement Products Online, Reinforcement mesh (standard sheet 4.8 × 2.4 m = 11.52 m²; overlap at least 350 mm; 50 mm cover with spacers)
- Reinforcement Products Online, Lapping mesh reinforcement (EC2 lap l0 = α1α2α3α5α6·lb,rqd ≥ max(0.3α6·lb,rqd, 15φ, 200 mm))
Results are calculations from the published methods and figures shown, and depend on the data you enter. Follow BS 8500, BS EN 206, BS EN 752, Building Regulations Part H, manufacturers’ data and your engineer’s design. Structural concrete and foundations need a competent designer.