Barrier Under Garden Room: How to Rodent Proof a Raised Floor Void

The specification requirements for a garden room sub-base barrier are the same as for any raised structure: welded wire mesh construction, clear mesh opening no greater than 8mm, wire diameter minimum 0.80mm, and hot-dip galvanised finish applied after welding. All four criteria must be met.

For garden room applications, the format of the product matters as much as the specification. Rigid mesh panels are difficult to deploy around screw pile positions and require complex cutting and joining around irregular pile spacings. A rolled mesh product can be fed around pile positions, lapped at joins, and adjusted to the site geometry without complex cutting.

The 1m width of BaseShield™ SubBase Defence is well-suited to garden room footprints. For a typical 5m × 4m garden room, five parallel runs of the 1m-wide mesh cover the full footprint with joins overlapped at each run edge.

The barrier must be installed before the floor frame is assembled. This means before the bearer frame is positioned over the pile or pad foundation, and certainly before any floor deck material is laid. Once the floor structure is in place, the full footprint is no longer accessible from above.

In a standard garden room construction programme, the correct installation point is after the piles are loaded and checked for level, and before the bearer frame is delivered to site. This typically adds 30–60 minutes to the groundworks programme — an investment that protects the full value of the building above.

For garden rooms supplied as a complete kit with delivery and installation by the manufacturer's team, the sub-base barrier should be specified in advance and included in the groundworks specification. Many manufacturers do not include it as standard — it must be explicitly requested.

If the garden room is already in place and you are looking to add sub-base protection retrospectively, full footprint coverage is not achievable without lifting the structure. However, a perimeter barrier — mesh dug in to at least 150mm depth and folded flat beneath the perimeter frame — provides meaningful secondary protection, particularly against burrowing rodents. This approach does not cover the full footprint but prevents the most common entry route.

For existing garden rooms where rodent activity is already suspected, address the active infestation before installing any exclusion barrier. Sealing animals inside the structure accelerates damage and creates additional problems.