The Permeable Paving Manual

The Permeable Paving Manual provides the comprehensive, detailed information on Concrete Block Permeable Paving (CBPP) necessary to satisfy National Planning Policy Framework (NPPF) and National Standards for SuDS: 2025 requirements. It covers all aspects and stages relevant to the various professions constituting the project design team, from master-planning through to engineering design and construction, and finally maintenance. Its primary aims are to ensure that CBPP delivers predictable, robust solutions and to minimise costs, maintenance and adoption issues. It encourages the use of pavement construction materials that are widely available. Early sections of the Manual provide a basic understanding of CBPP and Sustainable Drainage Systems (SuDS), essential for the effective use of detailed technical guidance later.

Essential Source Control

SuDS comprise a variety of physical structures that mimic natural drainage features and variously collect, clean and store runoff from development before release to the wider environment, in contrast with traditional piped drainage. A critical concept in SuDS - highlighted in the National SuDS Standards - is ‘source control’ that ensures relatively clean water flows onward along a ‘management train’ to an outfall from development.

The management train ensures that water continues to be cleaned as it passes from one SuDS feature to the next and is stored in a way that provides benefits for people and wildlife. Open basins, wetlands and ponds should always be protected from pollution and silt by being used at the end of the management train for the benefit of both people and wildlife.

The main generators of polluted runoff within housing developments are trafficked surfaces. Vehicles contribute tyre waste, hydrocarbons, metals and microplastics to road runoff which, with current conventional drainage regimes, washes directly into gully pots and pipe conveyance to watercourses, combined sewers and treatment works, or ultimately to the sea. Of course, safe, accessible hard surfaces are essential in all developments. Here, source control is the most important requirement in SuDS design, to ensure that clean water travels at the surface through the development landscape.

The only source control structure designed to collect, treat and store rainfall where it falls on trafficked hard surfaces, together with runoff from adjacent surfaces, is CBPP. It delivers a controlled flow of clean water for infiltration or as a source of clean water for amenity and wildlife enhancement. The importance of this technology to the successful roll-out of SuDS across developments is endorsed by independent SuDS experts.

Multifunctional SuDS Technique

The ability of CBPP to collect, clean and store large volumes of water from roads and parking sets it apart from other SuDS techniques. CBPP reduces the overall storage requirement for the site, freeing up space, and avoids the containment, risks and management issues of open SuDS features where silt and oil are collected. The multifunctionality of CBPP goes further, including efficient use of land and long-term maintenance of street trees – both current NPPF requirements – as well as enabling biodiversity and BNG. Removal of rainwater straight off the surface also avoids puddles and potholes.