Lined permeable car parks across Warwickshire

Clay underneath, rivers downstream

The Mercia Mudstone and Lias clays that cover most of the county drain too slowly for an unlined permeable car park to empty between storms. Downstream, the Avon and the Leam pass through Warwick, Leamington and Stratford, so the outflow from a new car park is usually limited. A lined sub-base solves both: it holds the storm under the bays and lets it go through a flow control chamber at whatever rate the consent allows.

Warwickshire's towns also have a lot of history underground. In Warwick, Stratford and Kenilworth, old foundations, cellars and buried services turn up whenever a car park is dug, and the formation often needs extra trimming and making good before it is ready. We look at it with the groundworker on the day rather than lining over a problem.

Where these car parks go

Tourism brings large visitor and coach parks to Stratford, Warwick and Kenilworth. Market towns are adding supermarket, health centre and station parking. In the north, logistics and manufacturing sites have staff car parks next to their yards, and where a site sits on old coalfield or filled ground, lining keeps rainwater away from it. National planning policy and England's 2025 SuDS standards each lean towards storing rain at surface level like this.

• Visitor and coach parks in tourist towns
• Supermarket, retail and health centre parking
• Staff car parks on logistics and industrial sites
• Station and park-and-ride sites

What we install

The groundworks team cuts the formation to the levels and falls on the drawing. Our first job is to confirm it: no ponding, no sharp hardcore, every area running down to its outlet. Then comes a non-woven geotextile over the base and up the edges, followed by the impermeable sheet in panels, fused with hot-wedge welders. A trial seam is peeled and logged before the main welding.

Outlets and overflows get welded collars, any services crossing the car park are booted through, the perimeter is turned up to the engineer's level, and a top geotextile shields the sheet from the stone that follows.

Programming the cover

An exposed liner is at risk from plant and weather, so we line in areas your contractor can cover with sub-base soon after. On a large visitor or staff car park that may mean several visits as each section is formed. Every visit adds to the weld records, which you receive at handover. If crates are built in under the parking for extra storage, we install those too.

On a town-centre site with shoppers and deliveries around it, we also agree working hours and a fenced area with the site manager so the lining isn't disturbed.