Ground Screw Rodent Protection: Rodent Barriers for Screw Pile Foundations

Ground screws and screw pile systems are increasingly used as the foundation of choice for garden rooms, modular buildings, garden offices and other raised structures. They are fast to install, cause minimal ground disturbance, work on sloped or uneven terrain, and do not require concrete.

These advantages come with a structural consequence. Unlike a perimeter wall foundation, a concrete strip, or a solid pad system, ground screws leave the full sub-base area open at ground level. The structure sits above multiple point contacts — the piles — with no continuous perimeter base. The void beneath the building is fully accessible from all angles.

This creates a specific rodent risk that is distinct from other foundation types. With a concrete perimeter foundation, rodents must burrow beneath or through the wall. With a ground screw system, there is nothing to burrow beneath. The void is open from every direction, at every point along the perimeter, and the only thing preventing rodent access is a ground-level barrier installed beneath the structure.

In practice, most screw pile installations for garden rooms and modular buildings are completed without any sub-base barrier. The foundation contractor installs the piles, the building contractor sets the bearer frame and builds above. Sub-base protection is not a standard specification item for this foundation type.

The result is a building with an open sub-base that is fully accessible to rats, mice and other wildlife from the moment it is completed. The insulation in the floor structure — directly above the void — is immediately available as nesting material. Service penetrations through the floor are potential routes into the interior.

The problem does not announce itself early. Activity typically begins within weeks to months of the structure being placed. By the time signs are visible — scratching beneath the floor, disturbed soil at the base of the piles, damage to the structure — a rodent territory is established and removal is difficult without closing the access point. For more detail, see our complete guide to preventing rodent access beneath raised structures.

Sub-base protection for screw pile systems must be installed before the bearer frame is assembled — ideally immediately after the piles are set, while the full ground area between them is still accessible. This is the key installation window. Once the frame is in place, access to the full footprint is restricted.

The barrier is installed flat across the ground between the pile positions. The mesh is fed around each pile shaft and lapped to close any gap at the pile contact point. The correct overlap at joins is 100mm minimum — this is important because the mesh is penetrated by the pile shafts and must be managed carefully at each penetration point.

At the perimeter, the mesh is turned upward against the outer bearer or frame, secured before the floor is built above. For screw pile systems with a high bearer frame, the mesh turn-up height should be at least 50mm to prevent rodents exploiting the edge junction.

BaseShield™ SubBase Defence is well-suited to screw pile and ground screw applications. The roll format (1m × 25m) allows the mesh to be fed around pile positions without the rigid handling difficulties of sheet materials. The 1m width is practical for working between pile spacings typical of garden room foundations.

The 7.66mm clear mesh opening and 0.80mm wire diameter meet the specification requirements for both rat and mouse exclusion. The hot-dip galvanised finish ensures long-term performance in permanent ground contact — important for a product that will never be accessible for inspection once the structure is built above it.

See our installation guide for step-by-step instructions including notes on working around foundation penetrations.