Welded wire reinforcement (WWR) is primarily used in slabs on grade to control cracking caused by shrinkage, thermal stresses, and other effects as well as to control crack width. Heavier styles of WWR can even be used as structural reinforcement in a slab.
It's relatively simple and inexpensive for contractors to properly support WWR in slabs on grade. Products available for this purpose include wire and welded-wire supports, individual high chairs with baseplates, bolsters with plates, all-plastic supports, and concrete blocks.
Soft base materials such as loose sand require supports with baseplates or with significant contact areas. Stiffer, more stable base materials allow the use of concrete blocks or wire and plastic supports without baseplates. Compacted granular fill is suitable for a variety of supports due to the inherent strength and stability of the gravel.
Generally, support spacings of 2 to 6 feet are recommended, depending on the stiffness and weight of the WWR being supported. (It is not necessary to stagger the supports). Spacing of the individual wires in WWR sheets should be 12 to 18 inches to avoid permanent displacement caused by workers walking on the reinforcement.