When applying reinforcement, often lapping length must be taken into account. Lapping length is the piece that one bar overlaps with another bar. This is necessary constructively to ensure that the tensile stress in the concrete is absorbed by the reinforcing steel.
Only when making completely prefabricated reinforcement, lapping length is no issue on the construction site, but due to transport (im)possibilities, workspace and price this is difficult to realize.
As a result, the reinforcement ( rebar cages , reinforcing mesh and rebar ) is often applied in separate parts on the construction site and these separate parts have to be linked by means of reinforcing steel with the correct lapping length.
In case of rebar cages, lapping bars are used or rebar cages with flying ends at one end. In case of reinforcing mesh there are several options: overlaying the mesh, use BEC mesh (with flying ends), coupling with joint mesh or applying lapping bars.
Every option has its advantages and disadvantages. The overlapping of the mesh creates unnecessary reinforcement, but goes quickly. BEC mesh are large and difficult to transport, but work very efficiently. When applying lapping bars there is no superfluous reinforcement, but it is time-consuming. The joint mesh are efficient and quick to apply and work well in small spaces.
To determine the correct lapping length, the Vereniging Wapeningsstaal Nederland (VWN) has developed a useful brochure, which takes account of the latest building standards / regulations (Eurocode).
In this diagram the most common diameters at good adhesion conditions. Check the brochure of the VWN for the exact conditions and other diameter.
