Gas membrane installation in Northamptonshire

Radon from the ironstone

The Jurassic Northampton Sand ironstone runs through much of the county, from the Daventry area through Northampton to Wellingborough, Kettering and Corby. Rock of this kind is associated with raised radon, and many plots across it need radon protection in new homes and extensions as a matter of course.

The site's radon assessment sets whether basic or full protection is needed. Full protection means a continuous barrier under the whole footprint, and that only works if every lap and service entry is sealed.

Brownfield land in the north of the county

Corby was a steel town, and the land around it was opencast for ironstone for decades. Former works, restored quarries and old tips mean made ground of uncertain make-up, sometimes with methane, carbon dioxide or oil residues. Similar questions come up on former industrial land in Northampton, Wellingborough and Kettering.

Where the ground investigation finds hazardous gas, the design follows BS 8485 and names the protection measures. We install the membrane part of that design.

What we do on the slab

We start from the specification and the gas risk assessment, then check the blinding or slab surface. Protruding aggregate or debris that could puncture the barrier is pointed out before we lay. Laps on a Northamptonshire slab are joined exactly as the product's specification sets out, by welding or by sealing, with no short cuts at corners or upstands.

Most failures we hear about start at a penetration, so on these slabs every pile head, soil pipe, cable duct and stanchion gets a purpose-made collar sealed to the sheet. If your warranty provider wants proof, we can bring in an independent inspector to test the barrier and certify it, and either way you get our own laying records for the warranty file.

• Radon barriers on housing across the ironstone
• Methane and carbon dioxide protection on made ground
• Hydrocarbon-resistant membranes on former industrial plots

Working round the frame

On housing sites the membrane often goes in plot by plot, between the groundworker's slab preparation and the bricklayers. We fit our visits to that rhythm so the barrier is laid, detailed and checked on each plot before anything else is built on it.