Permeable Paving is a surfacing system that allows rainfall to pass through the surface and into a granular sub-base, where it is stored, filtered and either infiltrated to ground or discharged at a controlled rate. It is one of the most widely-specified source-control SuDS components in UK urban developments.
Types of permeable paving
- Permeable concrete block paving — interlocking concrete blocks with enlarged joints filled with grit. Suitable for car parks, driveways, residential streets. Most common UK option.
- Porous asphalt — open-graded asphalt mix with 20%+ void content. Used for car parks and low-speed roads.
- Grass and gravel reinforcement systems — open-cell concrete or plastic grids filled with gravel or grass. Used for occasional-use parking, fire access, overflow car parks.
How it works in a SuDS context
A permeable paving system has three functional layers. The surface layer admits rainfall through enlarged joints, the open mix or the cell structure. A filter geotextile prevents fines from migrating into the sub-base. The sub-base — typically 200–400 mm of clean angular aggregate — provides the storage volume and infiltration or controlled outflow.
Where ground permeability is sufficient (k ≥ 1 × 10⁻⁵ m/s), the system infiltrates directly. Where it is not, an impermeable membrane and a flow control outfall are added.
Design and standards
UK design follows the Interpave guide (sixth edition) and CIRIA C753 The SuDS Manual. Hydraulic capacity, sub-base thickness, infiltration testing and outflow rate are all specified per the relevant chapters.
Maintenance is critical: regular vacuum sweeping (typically 2–4 times per year) is required to prevent clogging of the surface voids.
Related ViaCon solutions
ViaCon supplies underground storage and treatment components that integrate with permeable paving schemes. See our ViaCon Storm Solutions and the broader stormwater solutions range. Related glossary entries: SuDS, stormwater attenuation, soakaway and surface water drainage.
Frequently asked questions about permeable paving
What is permeable paving?
Permeable paving is a surfacing system that allows rainfall to pass through the surface into a granular sub-base. Common types are permeable concrete block paving, porous asphalt and grass/gravel reinforcement systems.
Does permeable paving count as SuDS?
Yes. Permeable paving is recognised in The SuDS Manual (CIRIA C753) as a source-control SuDS component. The sub-base storage volume can be counted towards stormwater attenuation requirements.
Does permeable paving need maintenance?
Yes — regular maintenance is critical. Vacuum sweeping is required typically 2–4 times per year to prevent fines clogging the surface voids.
Can permeable paving be used on driveways?
Yes — permeable paving is widely used on UK domestic driveways. Since 2008, paving new domestic driveways with impermeable surface over 5 m² has required planning permission, but permeable systems are explicitly exempt.