Welded Wire Fabric Specifications
Welded wire fabric, also called welded wire mesh, is a grid of metal wires contact-welded where they cross. While they may resemble the way fabric is woven, mechanically, they don't rely on a weave to stay together; they rely on the welded connection. There are two categories of welded wire fabric: the kind used for fencing and the kind used for concrete reinforcement.
Fencing
Welded wire mesh fencing comes in a wide variety of designs, grid sizes, wire gauges, lengths and heights. The typical wire mesh fence is used as a non-permanent fence. For example, it might be used to fence in small dogs or to keep deer out of a garden. Where permanent residential fences tend to be high enough to obstruct the view of a standing person, wire fence tends to be low -- 3 or 4 feet -- and does not serve as a visual barrier. It is usually lighter in construction than the concrete reinforcement type.
Concrete Reinforcement
Welded wire concrete reinforcement is similar in function to rebar. However, where rebar is designed to keep major structural concrete elements from displacing in case of cracking, mesh is designed specifically to reinforce monolithic slabs. When slabs are poured, like those in garages, the wire mesh is often installed before the pour so it becomes suspended in the concrete. The wire isn't as strong as rebar, but the mesh design will stop vertical displacement should the slab crack. It can also provide tension to hold a crack together.
Construction Grade
Like other construction materials, there is a very long list of specific sizes and configurations of welded wire mesh. If it is used as a key structural feature, the engineer or architect will specify the exact type of welded wire fabric to use -- or at least a range -- which falls within the strength requirements of the plan. In some residential applications, engineers or architects may not specify details on blueprints. They may simply call for its use in certain areas, meaning any construction-grade mesh will fill the need. If this is the case, however, it is important to use wire mesh intended for concrete reinforcement, not a lighter-duty fencing material. It sometimes comes in straight lengths or sheets. It also comes in rolls and will be sold with other concrete-related supplies at building centers.
Dimensions
Typical sizes of the mesh's square grids are 12 inches and 6 inches, though 4-, 3- and even 2-inch grids are available. The wire size or wire gauge is also available in a variety of sizes with larger grids tending toward the larger wire gauges. Sizes range from 16 gauge to 0 gauge, with the smaller numbers being larger diameters. Welded mesh is usually galvanized to resist corrosion once suspended in concrete. When you use welded wire mesh, the size should fit the size of your project, with larger mesh being used in large slabs. Installation may be even more important than size, as the mesh must be suspended properly in the concrete to provide proper counter-forces to fight displacement.
