Solving permeability problems

Duncan Andrews of SureSet looks at how cellular paving systems can offer the ideal solutions for SuDS requirements, in particular in sites with restricted space

Permeable paving solutions are a hot topic at the moment with an ever increase range of products and systems being brought to the market. Often it’s not the top surface that restricts permeability but the sub bases beneath it that ends up being the most restrictive factor. Some of the most widely available sub bases come from variations of asphalt and concrete, where the manufacturer will remove ‘fines’ from the mix and increase the ratio of larger aggregate particles to create a product with small voids, in that allows water to pass through in much the same way that resin bound paving performs.

For most applications this type of sub base is the best performing and most cost effective option when specifying permeable paving areas, but what about those projects with heavily restricted access such as roof terraces, courtyards or pathways between buildings, and those areas that require special attention such as tree pits and tree protection zones? Cellular grid structures offer strong, free draining and eco friendly solutions for areas with special requirements and are available in a wide variety of depths and materials.

Once laid they can be filled with a crushed and compacted aggregate or, in certain applications, a soil/planting mixture and sown with grass seed. This can then be left exposed as a finished surface, or used as a sub base to then install a permeable wearing course over, such as resin bound paving. Cellular paving is a rapidly expanding paving option due to its relatively low cost and simple installation process requiring minimal specialist tools and its low skill installation process.

Due to the simple installation methods, most cellular grid structures are available as supply only or supply and installation by the manufacturer/retailer. This allows onsite contactors the ability to complete the installation along with any other groundworks and landscaping before specialist teams come in to complete the final surface course works.

An example of when a cellular grid structure was the perfect solution to a project that required a permeable paving solution but had issues with access was on an installation at St Peter’s Church, in Battersea, London. The project involved the resurfacing of an enclosed courtyard and footpaths as part of a larger regeneration project of the whole building. The brief was to provide a permeable, low maintenance, attractive surface that could be enjoyed all year round by the members of the church community.

Access into the courtyard was restricted due to a low overhanging arch and pillars, meaning traditional sub base options such as tarmac or concrete were inappropriate. This meant the SureCell cellular grid structure could offer would provide the permeable sub base solution they required. The surfacing works were completed in June 2018 and included the supply and installation of both the cellular grid structure and the resin bound paving. Another benefit of using resin bound paving as a permeable surfacing solution is the wide range of colours and creative design possibilities that it allows.

For this project there was a requirement to differentiate the pathways and steps from the open courtyard area so two natural aggregate blends were chosen, a lighter shade for the courtyard and a darker shade for the paths and steps – which also matched the walls and brickwork of the courtyard.

Duncan Andrews is marketing communications manager at resin bound permeable paving manufacturer SureSet