How to Stop Rats Under Decking: The Structural Fix

Decking is not just a surface problem — it is a structural one. The moment a raised deck is built, it creates a horizontal sheltered void between the boards and the soil. That void is dry, warm, shaded, and almost entirely undisturbed. Rats, which are burrowing animals by instinct, recognise that environment and actively seek it out.

The access point is at ground level — not at the visible perimeter face, but beneath it. Rats burrow. They do not squeeze through gaps in skirting panels; they dig beneath the base of the structure from any angle at ground level. A garden with established decking has a permanent sub-base void that, without a barrier, will remain accessible to any rat in the area indefinitely.

The proximity of decking to kitchens, waste areas, bird feeders and compost bins makes the problem more likely. Rats are attracted by food availability near a reliable shelter. Once a colony establishes beneath a deck, they will extend their runs outward — to adjacent structures, wall cavities, and sometimes into the main building.

The most common responses to rats under decking — bait stations, foam sealants, chicken wire at the perimeter — all share the same flaw: they address the symptom without closing the structural access point.

Bait reduces a population but does not prevent re-colonisation. If the sub-base void is still accessible, rats from the surrounding area will move in once baiting pressure is reduced. Pest controllers will acknowledge that bait is a management tool, not a permanent fix.

Foam sealant is gnawed through within days. Expanding foam is not a physical barrier — it is a soft cellular material that rats remove with minimal effort. Chicken wire, which is often recommended as a cheap fix, has hexagonal apertures that are too large and inconsistent for rat exclusion, and the wire corrodes rapidly in soil contact.

Perimeter skirting — whether composite board, metal trim or timber — provides visual enclosure but no structural exclusion. Rats burrow beneath it. This is covered in detail in our complete guide to rodent access beneath raised structures.

The only method that reliably stops rats under decking long-term is a physical sub-base barrier installed at ground level beneath the full footprint of the deck. This is not a perimeter treatment — it is a full-footprint installation that removes the accessible void entirely.

The barrier must be welded wire mesh. The welded construction provides consistent aperture geometry and structural rigidity that woven or hexagonal mesh cannot match. The clear mesh opening must be no greater than 8mm — small enough to prevent rat entry without full body compression. The finish must be hot-dip galvanised after welding to resist corrosion in permanent ground contact.

Installation must happen before the deck frame is fixed, when the full ground footprint is accessible. The mesh is unrolled flat across the prepared ground, overlapped by 100mm at all joins, and secured at the perimeter before any frame or boarding is fitted above it. For a detailed walkthrough, see our step-by-step installation guide.

BaseShield™ SubBase Defence is designed specifically for this application. It is a rolled welded wire mesh product — 1m × 25m per roll, covering 25m² — with a 7.66mm clear mesh opening and hot-dip galvanised finish.

The roll format is practical for decking footprints. Long rectangular decks can be covered efficiently with parallel runs, minimal cutting, and clean overlaps at joins. No specialist tools are required. Installation adds between 15 and 30 minutes to the standard decking construction sequence.

See also: best barrier under decking and what type of mesh to use under decking.