Ground Screw Base Protection System
Ground screw and screw pile foundation systems are excellent for raised garden structures — fast, clean, and effective on difficult ground. But they create one of the most open sub-base configurations available in garden construction. Without a specified base protection system, the void beneath is accessible to rodents from every direction at ground level.
Why ground screw foundations require dedicated sub-base protection
A ground screw foundation system consists of a series of steel piles screwed into the ground at regular intervals across the building footprint. The bearer frame sits on the pile heads at a consistent height, and the building is constructed above. At ground level, the sub-base is defined by the pile grid — with no solid base, no continuous perimeter wall, and no material between the piles.
This means the sub-base is open from all sides. A rat or mouse approaching the structure from any direction at ground level has an unobstructed path into the sub-base void. There is no physical barrier at any perimeter point to delay or prevent access. The pile positions provide some vertical obstructions, but rodents navigate these without difficulty.
The openness is actually greater than in a traditional pad-and-bearer system, where the concrete pads at least provide some physical obstruction at the support points. In a screw pile system, the piles are narrow — typically 70–90mm diameter — and present minimal obstruction to sub-base access.
The correct base protection system for screw pile foundations
The base protection system for a screw pile foundation is a full-footprint ground-level welded wire mesh barrier, deployed after the piles are installed and before the bearer frame is assembled. This is the only approach that addresses the open sub-base comprehensively.
The barrier is deployed in parallel runs across the footprint. At each pile position, the mesh is worked around the pile shaft — either by threading the roll around the pile, or by making a small cut in the mesh to allow it to pass around the pile diameter. The cut is kept as small as possible and the cut edges are overlapped where possible to minimise exposed gaps.
The completed barrier — with all runs joined, perimeter edges folded upward and secured — covers the entire ground area beneath the building footprint. Rodents approaching from any direction encounter the mesh before they can access the sub-base above it.
Ground screw installation sequence with sub-base protection
The integration of sub-base protection into the ground screw installation sequence adds minimal time and disruption. The sequence is: (1) Ground screw installation to correct depth and position. (2) Pile heads levelled and checked. (3) Sub-base barrier deployed — BaseShield™ across full footprint, around pile positions. (4) Joins overlapped by 100mm and secured. (5) Perimeter edges folded and secured. (6) Bearer frame assembled over barrier and fixed to pile heads. (7) Floor frame, insulation, and deck proceed as normal.
Steps 3–5 represent the sub-base protection installation. On a standard garden room footprint (5m × 4m), this takes approximately 30–45 minutes for an experienced installer and 60–90 minutes for a first-time installation.
Maintenance-free operation after installation
Once installed and enclosed beneath the bearer frame and floor structure, the sub-base barrier requires no maintenance. It is a passive component that functions through its physical presence, not through any active mechanism. Hot-dip galvanised steel in ground contact has a lifespan measured in decades — long enough to outlast the floor structure above it.
The only operational consideration is ensuring the barrier is not damaged during the bearer frame installation. Care should be taken not to drag heavy bearers across the mesh surface in a way that might displace or tear the mesh. In practice, this is a minor consideration — the mesh is sufficiently robust to withstand normal construction traffic.
The right product for this application
BaseShield™ SubBase Defence is specifically designed for screw pile and ground screw foundation systems. The rolled format allows the mesh to be worked around individual pile positions — something that rigid panel products cannot achieve — and covers the full footprint in a single installation session.
BaseShield™ SubBase Defence
Forti NovaA purpose-built rolled sub-base barrier system designed specifically to prevent rodent access beneath raised structures. Supplied in 1m × 25m rolls — covering 25m² per roll — with a 7.66mm clear mesh opening and hot-dip galvanised finish applied after welding.
Roll size
1m × 25m
Coverage
25m² per roll
Mesh opening
7.66mm
Construction
Welded wire
Finish
Hot-dip galvanised
Wire diameter
0.80mm
Installation
Deploy BaseShield after piles are set and levelled. Work around each pile position as you unroll across the footprint. Overlap joins by 100mm. Fold the perimeter edge upward at the structure perimeter and secure before the bearer frame is assembled.
Read the full installation guideFrequently Asked Questions
Stop access beneath your structure
BaseShield™ SubBase Defence is installed during construction to provide permanent sub-base protection. Designed for garden rooms, modular buildings, decking and screw pile foundations.