Can Rodents Get Through Wire Mesh?

The common house mouse (Mus musculus) and the wood mouse (Apodemus sylvaticus) are significantly smaller than rats and can pass through gaps as small as 6–7mm in some circumstances. The skull of a house mouse is approximately 10mm wide at its widest point, but the animal can depress its skull bones slightly and compress its body through extremely small gaps.

This is the reason that standard hardware mesh with a 10mm or 12mm aperture — often sold as suitable for rodent exclusion — does not reliably stop mice. The critical threshold for mouse exclusion is a clear mesh opening of no more than 6–7mm. A 7.66mm opening, as used in BaseShield™ SubBase Defence, sits at the upper limit of reliable mouse exclusion for common UK species.

The shape of the mesh aperture affects exclusion performance independently of the nominal mesh size. A square welded mesh has consistent, predictable apertures that do not change under load. A hexagonal woven mesh (chicken wire) has variable apertures — the hexagonal geometry creates a range of effective opening sizes across the mesh surface, and those apertures distort further when the mesh is compressed by the weight of a structure above it.

This is one reason why chicken wire consistently fails as a rodent exclusion product despite having a nominal aperture of 12–19mm. The effective aperture at some points in the hexagonal geometry is larger, and under compression, the woven construction creates additional distortion. Mice that cannot pass through the nominal aperture find points in the mesh where the effective opening is sufficient.

Welded wire mesh with a sufficient wire diameter resists gnawing by all common UK rodent species. The critical specification is a wire diameter of at least 0.80mm. Below this threshold, rats with sustained motivation can gnaw through the wire in weeks. At 0.80mm and above, the wire is hard enough that gnawing does not make productive progress.

The welded construction also matters here. At each weld point, two wire strands are fused together — creating a junction that is harder and more resistant to gnawing than either strand alone. Woven wire products have no such reinforcement at their junctions, making them easier to gnaw and deform.

A mesh product with correct aperture size and wire diameter will still fail prematurely if the corrosion protection is inadequate. In permanent ground contact — the installation environment for a sub-base barrier — unprotected steel wire corrodes within years, reducing wire diameter and mesh strength to the point where it can be gnawed through or physically deformed.

Hot-dip galvanising applied after welding is the correct finish for sub-base barrier applications. The process coats every surface — including the weld points — with a zinc layer that provides long-term galvanic protection. Pre-galvanised wire, commonly used in cheaper mesh products, has bare metal at every weld point from the moment of manufacture. Those bare points begin to corrode immediately on ground contact.