What is the Best Mesh to Use Under Decking?

A sub-base barrier mesh must meet four criteria to be reliably effective over the lifetime of the structure. Each criterion matters independently — a product that satisfies three of the four will fail at some point, and the failure will be invisible until rodents are already established beneath the deck.

First: welded wire construction. The mesh apertures must be formed by wire strands welded at each intersection, not woven or twisted. Welded construction creates a rigid, dimensionally stable mesh geometry. The apertures are consistent across the full mesh surface and do not distort under load or over time. Woven and twisted wire products — including chicken wire — have apertures that distort with use, creating access points that were not present when the product was new.

Second: clear mesh opening no greater than 8mm. This is the dimension that determines whether mice can pass through. The clear mesh opening is the distance between wires — not the wire-to-wire centre measurement that some suppliers quote. A 10mm centre-to-centre mesh with 1.5mm wire has a clear opening of 8.5mm — sufficient for some mouse species to pass through. Always confirm the clear mesh opening, not the nominal mesh size.

Third: wire diameter of at least 0.80mm. Thinner wire can be gnawed through by rats within a surprisingly short time. A 0.80mm minimum wire diameter, combined with welded construction, provides adequate resistance to gnawing by all common UK rodent species.

Fourth: hot-dip galvanised finish applied after welding. The galvanising process must be applied to the completed mesh — not to the wire before welding. Pre-galvanised wire has bare metal at every weld point, where the welding process burns away the zinc coating. Bare weld points corrode rapidly in permanent ground contact. Post-weld hot-dip galvanising coats every surface, including the weld points, providing long-term corrosion resistance.