Open-textured Soil or Granular Material
These are gravel or similar surface on a sub-base. These are typically used in locations where low volumes of light weight traffic, such as cars, will be present and a low cost solution is required. There is little design and the use is restricted to locations such as pedestrian areas, driveways on private properties and temporary car parks.
Geo-synthetic Gravel/Grass Protection Systems
These are modular interlocking plastic paving systems which are in-filled with gravel/grass/aggregate and bedded on a free-draining structural sub-base layer. These are typically used for light to medium loadings such as car parks, or locations where occasional heavy vehicular loadings occur (i.e. refuse collection vehicles, removal lorries etc.)
Small Porous Elemental Surfacing Blocks
Precast blocks formed of low-fines concrete or other materials, which result in the blocks having many small, interlinked internal voids throughout their section.
These are laid on a recommended sub-base which has in the past varied from Type 1 sub-base (which is actually relatively impermeable) to clean gravel and crushed rock; or other open-textured support. Typical uses would be for public, engineered surfaces carrying high frequency, light loads such as shopping centre car parks.
Continuous Laid Porous Materials
This is porous asphalt, porous concrete or resign bound aggregate, laid on a recommended sub-base of free draining granular material. It will remain free-draining provided regular surface maintenance limits the deposit of debris in the surface void spaces. Typical uses are for public, engineered surfaces carrying high volumes of heavy and/or light loading, such as shopping centre car parks and service roads.
Continuous-laid Permeable Material
In situ cast concrete systems are available that provide a surface with large voids for infiltration, whilst offering hard standing for vehicles. The surface is unsuitable for small-wheeled trolleys and pedestrian use over large areas and has limitations aesthetically. Typically used in car parking areas.