The inclusion of wire mesh must be considered on a case-by-case basis, depending on the thickness and orientation of the shotcrete. Thin sections may well not have any wire mesh. In aggressive environments, at least 2 in. (50 mm) of shotcrete must cover the mesh. The mesh size should be at least 2 x 2 in. (50 x 50 mm) and preferably 4 x 4 in. (100 x 100 mm) to allow for proper encapsulation. Overhead shotcrete usually includes wire mesh for thicknesses greater than 2 in. (50 mm) in case the shotcrete debonds from the substrate. The mesh must be mechanically anchored.
Some designers are eliminating wire mesh and relying on synthetic fiber reinforcement for shrinkage crack control. The use of synthetic fiber eliminates the concern over cover and corrosion in aggressive environments. Specific recommendations on the amount and type of fiber should come from the manufacturer.