Gas membrane installation in Hampshire

Where the protection is specified

The need comes from the ground investigation, not from a map. In Hampshire it tends to follow the county's working history: reclaimed land and port estate around Southampton, the waterfront and former defence land in Portsmouth and Gosport, old gasworks and railway land in the larger towns, and landfill and backfilled pits on the edges of settlements.

Methane and carbon dioxide from made ground and fill are the usual triggers. Former fuel depots, garages and industrial yards can add hydrocarbons, which need a membrane rated to resist them. Your consultant sets the characteristic situation and protection measures to BS 8485, and we build to that design.

What makes a gas membrane work

A gas barrier fails at its joints and holes, rarely across the open sheet. Laps are welded or sealed to the specification, following the manufacturer's method and only in weather that suits the product. Piles, columns, drainage pipes and service entries are each collared and sealed individually.

Reclaimed land by the docks is soft, so buildings there are usually piled, and a slab spread over many piles is mostly detail. Ground beams, pile caps, lift pits and service trenches all step the membrane up and down. We work through those details in order, so nothing is left to be sealed in a hurry once the steel fixers arrive.

• Laps welded or sealed as the manufacturer specifies
• Preformed or site-made collars at each penetration
• Top hats and corners formed and sealed by hand
• Protection laid over the membrane where the design calls for it
• Records of every area and detail for the warranty file

Fitting into a Hampshire build

Most of the work is housing and commercial units on regeneration land, often on tight urban plots with piled foundations. We need the slab or blinding ready and clean before we lay: anything sharp or loose underneath can puncture the barrier, and we tell you on the day if the surface isn't fit to take it.

On higher-risk sites in Southampton and Portsmouth, warranty providers and building control often expect the membrane to be checked by someone independent. We can arrange integrity testing and a third-party validator to inspect it before it is covered. Our crews come south from Tamworth and fit around the frame and services trades.