Mesh Under Garden Room – Rodent Proof Barrier Specification and Installation
Installing the right mesh beneath a garden room is the most effective approach to permanent rodent proofing. But the specification matters — generic mesh from builders' merchants will typically not meet the requirements for reliable ground-contact rodent exclusion beneath a raised garden room.
Why generic mesh often fails beneath garden rooms
The mesh products commonly available for general garden or agricultural use are not designed for the specific requirements of a sub-base rodent barrier. They may have apertures that are too large for mouse exclusion, wire gauges too light to resist gnawing, or a galvanising process that will not perform long-term in ground contact.
The most frequent failure is aperture size. A 10mm or 12mm square welded mesh — sold for fencing or general purpose use — does not reliably exclude house mice, which can pass through gaps of 6–7mm. A 7.66mm clear mesh opening is the correct specification for a barrier that excludes both rats and all common UK mouse species.
The second frequent failure is galvanising specification. A pre-galvanised mesh — wire coated before welding — has bare metal at every weld point, which corrodes rapidly in ground contact. Hot-dip galvanising applied to the completed mesh covers all weld points and provides the correct corrosion protection for permanent ground-contact installation.
What mesh specification is required for a garden room sub-base
The correct specification for a garden room sub-base mesh is: welded wire construction, clear mesh opening of 7–8mm maximum, wire diameter of at least 0.80mm, and hot-dip galvanised after welding. This specification excludes mice and rats, resists gnawing, maintains aperture geometry under structural load, and provides long-term corrosion protection in ground contact.
The format of the mesh matters for practical installation. Rigid mesh panels are difficult to deploy around the pile positions common in garden room foundations, require complex cutting, and can be unwieldy to handle in a partly-constructed foundation area. A rolled product in 1m-wide runs is significantly more practical for the irregular geometry of a screw pile foundation.
How much mesh is needed for a garden room
Calculate the garden room footprint in square metres. Add 10–15% to account for overlaps at joins (minimum 100mm per join) and the perimeter fold detail. A 5m × 5m garden room has a 25m² footprint. With 15% added for installation allowance, you need approximately 29m² of barrier material — one roll of BaseShield SubBase Defence (25m²) and a small portion of a second roll, or a single roll if the footprint is smaller.
For garden rooms with irregular footprints — L-shaped, offset, or with protrusions for service connections — calculate each section independently and sum the total, then add the 10–15% installation allowance.
The installation sequence for a garden room
The mesh must be installed after the screw piles or pads are in position and before the bearer frame is assembled. Working from one end of the footprint, unroll the mesh across the first run. Thread around each pile position as required. When the run reaches the opposite end, fold the perimeter edge upward by 50–100mm and secure.
Begin the next parallel run overlapping the first by 100mm. Continue across the full footprint. At the final run, fold the remaining perimeter edges and secure. The bearer frame is then assembled directly over the completed mesh.
The right product for this application
BaseShield™ SubBase Defence is manufactured to the exact specification required for garden room sub-base protection. The 1m-wide rolled format is designed for the pile-foundation geometry common in garden room construction.
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
The rolled format of BaseShield makes it practical to deploy around screw pile positions without complex cutting. Thread the mesh around each pile as you unroll across the footprint. Overlap joins by 100mm and fold the perimeter edge before the bearer frame is set.
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.