Gas membrane installation in the New Forest

An honest picture of demand

A replacement house in a Forest village seldom has a ground gas problem, and we won't suggest one. Protection comes into play where the site investigation finds something: made ground along Southampton Water at Marchwood, Hythe and Fawley, backfilled gravel pits in the Avon valley near Ringwood, old tips and yards on the edge of towns, and land that once held fuel or chemicals.

Methane and carbon dioxide from fill drive most specifications. Close to the Waterside's industrial land, hydrocarbons may be in the risk assessment too. Your consultant sets the protection measures under BS 8485, and we install to that specification.

Installing the barrier

Before we lay, the slab or blinding is inspected. A sharp aggregate or a protruding bar under the membrane will puncture it, and we say so before work starts rather than after.

Joints in the sheet are welded or sealed exactly as the specification and product require. Piles, ducts, soil pipes and columns each get a fitted collar and a seal of their own, and the corners and steps are shaped by hand. We keep records of each area as we work.

Plots near the Waterside tend to be exposed and damp. A breeze across Southampton Water will lift a loose roll, and a wet slab ruins a sealed lap, so the membrane is laid in manageable bays and weighted as it goes. Where the weather turns, we stop and protect what is finished rather than rush a joint.

Validation and records

Warranty providers increasingly want proof on sites with a higher gas regime. We offer integrity tests and can bring in an independent validator on any job, and the installation records and any certificate are filed for the warranty provider.

• Specification review against the gas risk assessment
• Substrate check before laying
• Joints welded or sealed as specified
• Every penetration collared and sealed
• Validation available, records for the warranty provider