Rodent Barrier Under Shed Base: Specification, Timing & Installation

Garden sheds, log stores, bike stores, and small outbuildings sit on a raised base — timber bearers, paving slabs, or pressure-treated runners. Even where the clearance beneath the floor is minimal, the gap between the base and the ground is sufficient for mice to enter. A gap of 6–7mm is enough for an adult mouse to pass through.

The access point is almost always at the base perimeter — where the bearer or floor frame meets the ground surface. Over time, this gap widens as the structure settles. Timber bearers shrink and move. Gaps that did not exist when the shed was first placed open up at corners and along frame runs, creating entry points that are invisible from the outside.

Sheds are particularly vulnerable because they are typically positioned over garden soil — soft, easy to excavate — with food nearby. Bird seed, pet food, fertiliser, grass seed and garden chemicals stored inside provide an additional incentive. Mice will establish nests in insulation, stored materials and within the floor structure itself.

A sub-base barrier beneath a shed is not a perimeter seal — it is a full-footprint ground-level mesh that prevents burrowing access from any direction. The barrier is installed flat across the soil before the shed is positioned, extending slightly beyond the shed footprint at the perimeter.

This approach works because it removes the accessible void. Rodents cannot burrow beneath a correctly installed mesh barrier. They cannot gnaw through correctly specified welded wire mesh of the right gauge. And because the barrier is beneath the structure rather than around it, it does not degrade when the shed settles or the perimeter gap changes.

This is very different from applying foam sealant to the base perimeter or fitting a rubber draught seal to the door threshold. Those measures address a single access point. A sub-base barrier addresses all access points simultaneously. See our full guide to preventing rodent access beneath raised structures for the complete picture.

The most effective time to install a sub-base barrier is before the shed is positioned — at the point when the ground beneath the building footprint is fully accessible. This takes approximately 15–20 minutes for a standard shed footprint and requires no specialist tools.

For existing sheds that cannot be moved, a perimeter barrier — mesh secured tightly to the full base frame and pressed flat into the soil around the perimeter — provides meaningful reduction in access, though it cannot deliver the same level of protection as a full footprint installation. If the shed is being relocated or replaced, that is the correct moment to install a full sub-base barrier.

The barrier should extend 50–100mm beyond the shed footprint at the perimeter and be turned upward against the base frame. This prevents rodents exploiting the edge junction where the barrier meets the structure.

The barrier must be welded wire mesh — not hexagonal chicken wire, woven wire or plastic mesh. The clear mesh opening must be no greater than 8mm to prevent mouse entry. The wire must be of sufficient diameter to resist gnawing — a minimum of 0.80mm. The finish must be hot-dip galvanised after welding to withstand ground-contact conditions without corrosion.

BaseShield™ SubBase Defence meets all of these requirements. With a 7.66mm mesh opening, 0.80mm wire diameter, and hot-dip galvanised finish, it is designed for permanent ground-contact installation in exactly this application. Each roll covers 25m² — sufficient for most domestic shed footprints in a single roll.