Car park lining in Birmingham

Why so many Birmingham car parks are lined

A permeable car park lets rain through the paving into a stone sub-base. Whether that sub-base can then drain into the ground depends on what lies underneath. East of the city centre the mudstone barely takes water. On brownfield plots the investigation often rules out infiltration because it could move contamination. And on a tight urban site the parking may sit hard against foundations and basements.

Faced with any of those, the engineer draws a lined pavement. The stone layer then works as a shallow reservoir under the bays, releasing what it holds through a flow control at whatever rate planning agreed.

Sites we line across the city

Each type of site brings its own programme. A retail car park may be built in phases to keep the store trading; a school one may have to be done in the holidays. We fit around both.

• Supermarket and retail park car parks
• Hospital, college and office parking
• Park-and-ride and station car parks
• School drop-off areas and staff parking
• Housing courtyards and shared parking areas

What goes under the stone

Our part starts once the groundworker has cut the formation to its falls. We walk it looking for proud stones, soft patches and any low spot that would hold water away from an outlet, and agree fixes before laying anything.

Next a non-woven cushion fleece covers the floor of the dig and climbs its walls. Over that, we unroll the impermeable sheet a panel at a time and fuse each join with a heat welder, and the day's trial weld is cut and logged. Each outlet and overflow, and any duct crossing the car park, is sealed into the sheet, the sheet's edges are lifted to the height the drawing gives, and a top fleece goes over everything to shield it from the stone.

Busy city sites

Birmingham car parks are often built next to a store, ward or school that stays open. We work inside the groundworker's fenced area, keep the welding kit and rolls tucked out of the way of site traffic, and phase the lining to suit the order in which bays come out of use.

After we hand over

Your contractor brings in the stone and then the paving. Handing over area by area means the sheet is buried quickly, and on a busy Birmingham site cover is the best protection it can have.