What is a 'wearing course' in a car park?

The wearing course is the topmost layer of a car park deck coating system. It is the sacrificial layer that takes the physical abuse of tyres, braking, and turning. It is usually heavily aggregated (with quartz or bauxite) to provide anti-slip properties. Protecting the waterproofing membrane beneath it is its primary job. When the wearing course wears down, it must be recoated to prevent damage to the critical waterproofing layer below.