Car park lining in Manchester

Why the sub-base gets a liner here

Permeable paving lets rain through the surface into a deep stone layer. On free-draining ground the water would carry on down. Across most of Greater Manchester it can't: the till takes water too slowly, and on former industrial land the engineer won't let runoff wash through contaminated fill. A welded membrane under the stone turns the sub-base into an attenuation store that empties to the drain through a controlled outlet.

Planning conditions across the conurbation cap discharge rates, and the 2025 national SuDS standards favour surface features like this over pipes and tanks alone. Lined permeable paving gives the storage and the SuDS treatment in the same footprint as the car park.

The car parks we line

Retail parks along the A6 and the Trafford corridor, supermarket extensions, hospital and university car parks, Metrolink park-and-ride sites, and the yards and staff parking at logistics parks near the M60 junctions. Where the stone layer alone falls short of the design volume, the engineer may add crates beneath one corner; we build those as well, so a single team and a single record set cover the lot.

On site, layer by layer

Excavation and grading to falls are handled by your groundworks team. Before we unroll anything, we check it for level, loose stones and a steady fall towards each outlet.

• Fleece over the base and side walls
• Membrane panels, heat-welded
• One logged test weld per job
• Outlets and crossings sealed in
• Upper fleece to guard the sheet

Handover and covering up

Each finished area comes with its weld log and handover sheet. On a busy retail scheme we line in sections that match the paving sequence, so no area of membrane sits exposed to traffic or weather for long, and the stone can be tipped onto it the same week.

Manchester rain helps nobody on an open formation. If water has ponded in the dig, we ask for it to be pumped out and the base checked again before welding resumes.

Old foundations in the dig

Excavating a car park on former mill or works land in Manchester often turns up old footings, brick rubble and redundant pipes. They need to come out, and the formation needs to be trimmed smooth, before any fleece goes down. A snapped brick edge left in the base can push through a membrane once a loaded stone layer and cars sit on top.

We walk the formation with your site manager and mark anything that has to go. It is far quicker to deal with it then than to cut out and patch a welded sheet later.