Rodents Under Decking: Rats, Mice, Foxes & Prevention with Barriers

Raised timber and composite decking creates a sheltered horizontal void between the deck surface and the ground. That void is protected from rain, shaded from sun, insulated by the boarding above, and almost completely undisturbed by people. For a wide range of animals — rats, mice, foxes, hedgehogs, frogs and cats — it is an appealing place to shelter or nest.

The access point is almost always at ground level. Decking sits on bearer joists above the soil, with a gap of anything from 50mm to 300mm beneath the frame. There is no sealed perimeter in the structural sense — just a visible fascia at finished deck height, which does nothing to prevent animals burrowing or squeezing under the frame edge.

Most decking in domestic gardens is positioned close to the house, near a kitchen door or patio area. That proximity to food sources — waste bins, composting areas, bird feeders — compounds the attraction. A sheltered void adjacent to reliable food is exactly the kind of environment rats in particular will actively seek out and defend.

The first signs are often heard rather than seen. Scratching, rustling or movement beneath the boards — particularly in the evening or early morning — is the most common early indicator. Rats are most active around dusk and dawn; foxes may be heard at night.

Visual evidence at the perimeter is usually the next sign: disturbed soil, scraped earth at the frame edge, or small entrance holes excavated beneath the bearer or frame. Rats will establish defined runs along the inside edge of the frame, compacting the soil into visible tracks.

Droppings near or beneath the decking, damage to irrigation pipework, gnawed cabling or insulation, and scattered nesting material at the perimeter are all indicators of established activity. By the time these are visible, the problem is usually well-established.

The instinct is to treat the symptom — bait stations around the decking, blocking visible holes with expanding foam or rubble, fitting skirting at the perimeter. Each of these may temporarily reduce activity but none of them closes the structural vulnerability.

Foam sealants are gnawed through by rats within days. Rubble can be shifted by burrowing animals with moderate effort. Perimeter skirting, however solid it looks, is fitted at finished ground level. Animals burrow beneath it — the soil beneath is soft and undisturbed, and rats in particular will excavate beneath a skirting panel in hours if there is harbourage on the other side.

Bait programmes reduce populations but will not prevent re-colonisation. If the sub-base void remains open and conditions remain attractive, animals will return. The structural access point is the problem that needs to be addressed — not the individual animals.

A ground-level physical barrier installed across the full footprint of the deck is the only reliable solution. The barrier must be positioned flat at soil level beneath the entire structure — not just at the visible perimeter edge. This is because animals, particularly burrowing species, will enter from any direction and at any point along the perimeter. A perimeter-only barrier leaves the full interior of the sub-base void open to access via burrowing beneath the barrier edge. For the full technical picture, see our guide to preventing rodent access beneath raised structures.

The material must be welded wire mesh — not hexagonal chicken wire, which has inconsistent apertures and corrodes rapidly in ground contact. The mesh opening must be small enough to exclude the target species. For rats and mice, that means a clear mesh opening no greater than 8mm. For the product to last in permanent ground contact, it must be hot-dip galvanised after welding.

The correct installation window is during construction, before the deck frame is fixed. At that point the full ground footprint is accessible, the mesh can be positioned flat across the entire area, overlapped at joins, and secured at the perimeter before any superstructure is in place.

BaseShield™ SubBase Defence is a rolled welded wire mesh barrier with a 7.66mm clear mesh opening, 0.80mm wire diameter, and hot-dip galvanised finish. Each roll covers 25m² (1m × 25m) — a format that is practical for decking installations of any size.

The roll format means faster installation with fewer joins than cut-to-size mesh panels. For long rectangular decking footprints, a single roll laid lengthways often covers the full area in two runs. Rolls are overlapped by 100mm at joins, with the perimeter edge turned upward against the frame before the deck boards are fitted.

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