Does a permeable sub-base (load-bearing layer) need to be installed with a slope?

A permeable sub-base (technically, a permeable load-bearing layer) can generally be constructed without a slope, as rainfall in this case naturally percolates into the ground. This is not only significantly more cost-effective than artificial drainage via a rainwater sewer system, but also ecologically sound, because the infiltration surface supports the natural water cycle and groundwater formation. However, it is essential that the wearing surface also exhibits high permeability, so that the entire system enables effective infiltration. Rubber granulate tiles are particularly well suited for this purpose, being available for terraces, playgrounds, and many other outdoor areas. Suitable rubber granulate floorings typically offer a permeability of 200 litres per hour per square metre or more.