Rodent Barrier Mesh Under Decking: The Right Specification

The search term covers several different use cases. Some people want to stop rats and mice. Some are concerned about foxes or other wildlife. Some have been recommended mesh by a pest controller or builder and want to understand what to buy. And some have already tried chicken wire and found it ineffective.

What unites these searches is a common problem: an open sub-base void beneath a raised deck that is providing access for something that shouldn't be there. The answer in all cases is the same — a correctly specified welded wire mesh barrier installed flat at ground level beneath the full footprint of the deck.

The mesh itself, however, is not interchangeable. The type of mesh, the mesh opening size, the wire gauge, and the finish all determine whether the product works. This page explains what to look for. For the broader context of why sub-base barriers matter, see our complete guide to rodent access beneath raised structures.

Welded wire mesh — not hexagonal. This is the single most important distinction. Hexagonal mesh (chicken wire) has apertures that are formed by twisting wire around itself, not welding it. The apertures are inconsistent in size — the same sheet may have openings that vary significantly across its surface. The wire used is typically much lighter gauge and the product corrodes rapidly in ground-contact conditions. It is a poultry management material. It is not a sub-base rodent barrier.

Mesh opening size. The clear mesh opening — the gap inside the wire boundary — must be no greater than 8mm to exclude mice. Juvenile mice can pass through gaps of approximately 6–7mm. Rats are larger but will exploit any gap that allows partial entry if repeated pressure can widen it. A consistent 7–8mm welded aperture provides effective exclusion of both species.

Wire diameter. Minimum 0.80mm for ground-contact use. Lighter wire can be gnawed through by rats given sufficient motivation. A 0.80mm welded construction provides meaningful resistance without adding unnecessary weight or handling difficulty.

Finish. Hot-dip galvanised after welding. The critical word is 'after' — galvanising applied before welding leaves the weld point unprotected. In ground contact, unprotected weld points corrode first, weakening the mesh at its joints. Hot-dip galvanising after welding ensures that every joint and every wire surface is protected.

Mesh for under-decking use is available in cut panels and in roll format. Cut panels — typically rigid welded mesh in sheet form — must be templated, cut, and fitted around foundation details. Every join between panels is a potential gap. On a complex footprint with multiple post contacts, the number of joins increases rapidly. Each one is a risk point.

Roll format mesh is significantly faster to install and produces fewer join points. A 1m wide roll can be positioned in parallel runs across the footprint, overlapped by 100mm at joins, and secured at the perimeter without the handling difficulties of rigid sheet materials. For domestic decking installations, a single roll often covers the full footprint in one or two runs.

BaseShield™ SubBase Defence is manufactured to the correct specification for use under decking: 7.66mm clear mesh opening, 0.80mm wire diameter, hot-dip galvanised after welding, 1m × 25m roll (25m² per roll).

It is the product closest to what the search intent for 'mesh under decking' is actually looking for — a purpose-built sub-base barrier in roll format, designed for installation beneath raised domestic structures.

For installation instructions, see our step-by-step guide.