What is permeable paving and how does it improve SuDS on patios and driveways?

The risk and devastating effect of floods in the UK is growing, and permeable paving is being put forward as one of the solutions.

Permeable paving allows water to soak into the ground beneath it, instead of pooling like it would on a solid surface. It is one of many sustainable drainage systems, or SuDS, which will become a legal requirement for new homes from next year.

We spoke to flood expert Graham Brogden MBE, of the BeFloodReady Centre in Oxfordshire, about this important aspect of home construction.

What is permeable paving?

Permeable paving provides a surface that supports pedestrians and vehicles but allows rainwater to pass through the surface and soak into the structure or ground underneath, rather than running off into drains. It is increasingly used as part of SuDS – or sustainable drainage systems.

There are various types of materials used in permeable paving, including gravel, porous concrete or asphalt, and even permeable interlocking concrete pavers. You may have seen these used on drive ways and car parks, as they provide a solid surface for cars to drive on, yet the open joints facilitate water drainage.

Permeable paving surface coverings helps to manage water runoff following rain, and therefore helps to reduce the risk of surface water flooding. It can also treat some of the pollutants in runoff and aids the recharging of groundwater, which can have several environmental benefits. Options to buy include special grates to strengthen gravel surfaces like this Ecobase porous paver base from B&Q as well as permeable block pavers themselves like these options from Simply Paving or these paving packs from Travis Perkins.

While the two can be used hand-in-hand on driveways, permeable paving is different to a soakaway, which is a type of SuDS comprised of underground structures, made of stone and rubble, that collect and disperse surface water into the surrounding soil, boosting natural drainage. 

We cover them in greater detail in our ‘what is a soakaway’ and ‘how to build a soakaway’ articles.

How permeable paving prevents flooding

Permeable paving allows rainwater to infiltrate into the ground rather than accumulate on the surface.

When heavy rainfall occurs, a permeable surface will absorb and store the water temporarily, which then gradually infiltrates into the soil below or slowly drains into drainage and sewers.

This reduces the build-up of significant volumes, not to mention the velocity, of surface runoff. We frequently see ‘rivers’ of runoff rushing down roads and pavements following a heavy downpour in urban areas as the water has nowhere to go.

Instead, permeable paving minimises the risk of flooding and relieves the pressure on the drainage infrastructure.

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Why permeable paving is a SuDS solution

Permeable paving works differently from regular paving in that it allows water to pass through the surface rather than running off it. 

Regular paving, such as concrete, is impermeable which means water cannot penetrate it and instead flows over the surface. This has the potential to cause flash flooding when significant rain occurs.

Permeable Paving offers several benefits over and above flood prevention, including groundwater recharge and pollution control. It is important to mention that its effectiveness does depend on proper design, installation, and maintenance.

It may not also be suitable for every situation but it is a valuable tool in the SuDS toolkit and should be considered wherever possible.

The adoption of permeable paving can contribute to meeting the legal requirements for SuDS in new developments.

How SuDs are becoming a legal requirement

SuDS are becoming a legal requirement from 2024 due to the Flood and Water Management Act of 2010. This legislation was introduced in response to significant flooding events, such as the widescale floods of 2007, which caused extensive damage to properties and infrastructure.

The act aims to improve flood management and reduce the risk of surface water flooding and sewage pollution.

By making SuDS mandatory in new developments, the government aims to ensure more resilient and sustainable drainage systems that can effectively manage rainwater runoff and mitigate flooding risks.

It is certainly considered a good SuDS technique because it addresses the objective of managing stormwater on-site close to the source of rain and on the surface as well as promoting responsible water management practices overall.