Car park lining in Leicestershire

A storage layer under the paving

On free-draining soil, a permeable car park can let rain soak straight through. Most Leicestershire sites sit on mudstone, Lias or boulder clay instead, so the design captures the water in the sub-base and releases it slowly through an outlet. The lining is what makes that sub-base watertight, turning the whole car park into a shallow attenuation store.

Where the paved area can't hold all the design volume, crates often go in underneath. We install both, under one set of records.

Retail, campus and park-and-ride sites

Large car parks attract the closest attention from drainage engineers and planners. In Leicestershire that means the retail parks on the edge of Leicester, the city's park-and-ride sites, university campuses in Leicester and Loughborough, hospitals, and business parks at Hinckley, Lutterworth and along the A42.

Smaller jobs come up too: a surgery or village hall extension, or a school adding staff parking, where the same clay rules out a soakaway.

Working on a clay formation

Clay is unforgiving once it's wet. A formation that was firm in the morning can be rutted by plant after a shower. Your groundworker trims it to the design falls; we check it's firm, smooth and running to the outlets before laying anything. If it has softened, we'll ask for it to be put right first.

• Non-woven fleece over the clay and turned up the edges
• The impermeable sheet laid in panels and hot-air or wedge welded
• A trial weld cut and logged on the same day
• Outlet pipes, overflows and crossing ducts booted into the sheet
• A covering fleece laid ahead of the stone

Handing back to your programme

Our weld log goes to the site manager on the day, and from there the stone and blocks are in your groundworker's hands. Getting cover on quickly protects the membrane from site traffic, so we plan our visit around the day the sub-base can follow, rather than leaving a finished liner exposed over a weekend.

On a long retail or campus car park we can line in bays, leaving each edge protected so the next bay can be welded on when the groundworker reaches it.