Sub-Base Barrier System for Builders and Garden Room Installers

The sub-base barrier is installed as part of the groundworks programme, after the foundation elements (screw piles, concrete pads, or adjustable supports) are set and before the bearer frame or joist frame is delivered to site. This is the natural installation window — the ground is clear, the foundation positions are known, and the full footprint is accessible.

For screw pile foundations: piles are drilled, set, and checked for level. The barrier mesh is then deployed across the footprint, threaded around each pile position, overlapped at joins, and secured at the perimeter before the bearer frame is assembled over it.

For pad foundations: pads are set and levelled. The barrier mesh is deployed across the full footprint between and around the pad positions. The mesh may need to be slit at pad positions to lay flat around the pad edges.

For adjustable steel feet: the barrier is deployed before the feet are locked at their final position. The mesh is slit at each foot position if required. The bearer frame is then set onto the feet over the barrier.

Calculate the structure footprint area in square metres. Add 15% for installation allowance (overlaps, perimeter folds, waste). Divide by 25 to get the number of BaseShield rolls required. Round up to the nearest whole roll.

Example: a 6m × 5m garden room has a 30m² footprint. Add 15%: 34.5m². Divide by 25: 1.38 rolls. Round up: 2 rolls. Standard residential garden rooms typically require 1–2 rolls. Larger modular buildings and multi-section decking installations may require 3–5 rolls.

A correctly installed sub-base barrier should be documented as part of the build handover. Key installation standards to confirm: full footprint coverage verified (no gaps or unbridged sections), all joins overlapped by minimum 100mm, perimeter edges folded upward and secured, mesh in consistent ground contact across full area.

Photographic documentation of the installed barrier before the floor frame is set provides a clear record for the homeowner. This demonstrates due diligence and provides confirmation if the specification is ever queried.