Sub-Base Mesh Barrier – Technical Guide
A sub-base mesh barrier is a welded wire mesh product installed flat at ground level beneath the full footprint of a raised structure before the floor frame is set. It prevents rodents and other animals from burrowing into the sub-base void — the space between the ground and the underside of the floor — by providing a physical barrier at ground level.
How a sub-base mesh barrier works
The barrier works by interrupting the burrowing approach that rodents use to access sub-base voids. When a rat or mouse attempts to burrow beneath the edge of a structure, it encounters the mesh at ground level — before it can excavate into the sub-base space. The animal cannot burrow through the welded wire mesh and cannot gnaw through a correctly specified product within any practical timeframe.
The critical feature is that the barrier is at ground level — not suspended beneath the floor, and not fixed only at the perimeter. A perimeter-only installation can be circumvented by burrowing inward. A ground-level full-footprint installation cannot, because the entire ground area within the structure footprint is covered.
The mesh is permeable to water and air, so it does not act as a membrane and does not affect sub-base drainage or ventilation. This distinguishes it from a damp proof membrane — it provides physical exclusion without hydrological effects.
Technical specification for a sub-base mesh barrier
The specification for a sub-base mesh barrier must address four performance requirements: rodent exclusion by aperture size, gnaw resistance by wire strength, dimensional stability under structural load, and long-term corrosion resistance in ground contact.
Aperture size: the clear mesh opening must not exceed 8mm for reliable exclusion of all common UK rodent species including juvenile mice. The clear opening is the gap between wires, not the centre-to-centre dimension. Confirm the clear opening with any supplier.
Gnaw resistance: the wire diameter must be at least 0.80mm. This is the minimum dimension at which common UK rat species cannot gnaw through the wire within a practical period. Thicker wire provides additional reserve capacity.
Dimensional stability: welded wire construction — wires resistance-welded at each intersection — maintains consistent aperture geometry under the compressive load of a structure built above it. Woven or twisted wire products deform under compression and cannot maintain their specified aperture size.
Corrosion resistance: hot-dip galvanising applied to the completed mesh after welding. This process coats all surfaces including weld points. Pre-weld galvanising leaves weld points uncoated and provides inadequate long-term protection in ground contact.
Installation standards for a sub-base mesh barrier
A correctly specified mesh barrier will underperform if incorrectly installed. The key installation standards are: full footprint coverage (no gaps), minimum 100mm overlap at all joins, perimeter edge folded upward by 50–100mm and secured, and correct ground contact across the full mesh area.
Joins are the primary installation failure point. A single join with insufficient overlap is sufficient for mouse entry — particularly if the join is not secured and the mesh edges lift slightly over time. Each join must be lapped by 100mm, with the upper layer overlapping in the direction of expected animal approach (outward to inward).
Perimeter detailing is the secondary failure point. The mesh edge at the structure perimeter must be folded upward against the outer frame or foundation and secured so it cannot lift. Any gap at the perimeter edge — even a few millimetres — can be exploited by mice.
The right product for this application
BaseShield™ SubBase Defence is manufactured to all four technical specification requirements for a sub-base mesh barrier. It is supplied in rolled format specifically suited to the installation approach required for raised structure groundworks.
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
Install BaseShield before the floor frame is positioned. Deploy in parallel runs, overlap joins by 100mm, fold the perimeter edge upward and secure. The floor frame is then positioned directly over the completed barrier.
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.