Mesh (or fabric) reinforcement is a convenient way of using pre-assembled sheets of reinforcement bars. It is made up of wires, welded together. The wires are usually ribbed type 2.
The relevant standard is BS4483:2005 “Steel fabric for the reinforcement of concrete”. This BS gives the preferred range of fabrics as below. It should be noted that many of the types are rarely used and availability should be checked before specifying. It should also be noted that the traditional A98 is no longer in the range, although the identical D98 still remains.
 The decision whether to use mesh instead of loose bars is largely dependent on the shape of the precast unit.
Stock size of standard meshes is 4.8m x 2.4m.
If a unit is larger than a stock sheet, then lapping will be necessary. Lapping requirements for two sheets of mesh is covered by BS8110 cl 3.12.8.5. If the lap occurs at the middle of a panel, then the minimum lap length for an ‘A’ mesh must include 4 welded cross wires. This infers a minimum lap length of (3 @ 200 + 100) = 700mm. Care should be taken at laps since the overall space required for several sheets could become excessive. If the quantity merits it, consideration should be given to special sheets, (see below for detailing rules.)
An alternative to lapping sheets of mesh may be to ‘lap’ using loose bars. In this case the lap length will be determined by the standard ‘rules’ based on bar diameters.
 The normal edge detail for ‘A’ mesh sheets is as shown left. If the sheet is cut then the overhang may be even higher, up to nearly 200mm. In these cases, if this occurs at a face of the concrete, a loose edge-trimming bar should be added to the end of the cross wires with (typically) 50mm cover. The diameter of this trimming bar should be as the adjacent wire.
Mesh reinforcement is also available in stainless steel, although checks should be made on availability and delivery times. Typically available standard sizes in stainless are A393, A252, A142, D98 & D49. A 100 x 100 x 5mm mesh is also available.
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