These high-strength, accurately made spacers should be used to
ensure the joint widths required for permeable paving. Stone cannot
readily be produced with nibs as can concrete paving; these nibs both
manage the joint width and provide strength. With stone, this has to be
provided with the spacers and tuffgrit as the jointing aggregate. The
calculations for SuDS purposes are the same whether using stone or
The picture shows a selection of the types available. They can
provide joints from 5 to 50mm. Some are used at the junctions between
units and some in strips. The wide joints can be infilled with soil if a
growing medium is required.
Permeable systems with spacers are not advised for the public
highway, but some types may be used up to traffic category 5 (pedestrian
areas subjected to occasional overrun of commercial vehicles and car
parks receiving occasional commercial vehicular traffic). They are
suitable for private drives that need to be SuDS compliant.