Garden Room Base Protection: Rat Proofing the Sub-Base Void

When people talk about garden room base protection, they typically mean one of two things: protecting the structure from damp and moisture, or protecting the sub-base void from unwanted access. These are not mutually exclusive — both matter — but they require different approaches and are addressed at different stages of the build.

This page focuses on the second: preventing access through the open sub-base void beneath a raised garden room. This is the aspect most commonly overlooked during construction, and the one most likely to cause significant problems over the lifetime of the building.

A garden room built on screw piles, adjustable feet, bearer rails or concrete pads sits above ground level. The space beneath the floor is a sheltered, enclosed void that is accessible from ground level. Without a physical barrier installed across the full footprint, that void is open to rodents, wildlife, and other unwanted access for the full lifetime of the structure.

The sub-base void beneath a garden room is not only a rodent risk. Any open void at ground level in a domestic setting is an access point. Foxes may use the space for denning. Cats — feral or domestic — may shelter beneath the floor in cold weather. Hedgehogs, slow worms and other wildlife may nest in the undisturbed ground beneath the structure.

Some of this may be tolerable. Rodents — rats and mice in particular — are not. They cause structural damage to insulation and timber floor members, create contamination through droppings and urine, and present potential routes into the interior of the building through service penetrations and floor junctions. The consequences of an unaddressed sub-base rodent problem in a garden room used as a habitable space are significant.

A ground-level mesh barrier addresses all of these access concerns simultaneously. It does not need to be targeted at a specific species — it closes the void to anything attempting to enter at ground level or by burrowing.

The correct time to install a sub-base barrier for a garden room is during the construction phase, before the floor frame is set. At this point the full ground area beneath the building footprint is accessible, the mesh can be positioned flat across the prepared surface, overlapped at joins, and secured at the perimeter before any superstructure is in place.

Retrofit installation beneath a completed garden room is significantly more difficult. Access to the full footprint is restricted by the floor frame. Achieving proper mesh coverage at joins and penetration points is harder. For a structure that is already built, a perimeter barrier — mesh secured to the base frame around the full perimeter — provides partial protection, but cannot replicate the coverage of a full footprint installation.

Full installation details are provided in our step-by-step installation guide. For context on why this matters, see our complete guide to preventing rodent access beneath raised structures.

BaseShield™ SubBase Defence is a purpose-built rolled sub-base barrier system designed for installation beneath garden rooms and other raised structures. The 7.66mm clear mesh opening excludes all common UK rodent species. The hot-dip galvanised finish is designed for permanent ground contact. Each roll covers 25m² — sufficient for most garden room footprints in one or two rolls.

BaseShield is a construction component, not a pest control product. It is specified at the build stage and installed in 15–30 minutes as part of the standard foundation sequence — not retrofitted after a problem is discovered.