Everything You Need to Know About SuDS for Extensions and Small-Scale Developments

Why SuDS?

Sustainable Drainage Systems (SuDS) are features designed to mimic natural drainage processes. Instead of directing rainwater into conventional drains, SuDS manage runoff at the source, allowing rainfall to infiltrate the ground, evaporate, or even be reused.

You may think that SuDS are only for new large housing or commercial developments, but not all SuDS need to be regionally sized ponds, wetlands or swales to be effective. For smaller-scale developments such as extensions, significant betterment can be gained by retrofitting SuDS within your property.

SuDS and Planning

While the environmental benefits of SuDS are clear, there are practical reasons to consider them for small house extensions. The main reason is compliance with planning regulations. Over the past couple of years, we have noticed a trend that Local Planning Authorities are asking for SuDS to be considered on more and more small-scale developments.

We understand that there is nothing more frustrating than a planning application being refused or delayed because SuDS/surface water drainage has not been considered. By incorporating SuDS at the earliest possible time during the planning phase of the project, it can streamline the approval process.

Are SuDS a Legal Requirement?

Not yet. But SuDS will soon be a legal requirement for all new developments. Earlier this year, it was planned for Schedule 3 of the Flood and Water Management Act 2010 to be implemented in England. However, some local authorities have chosen to take it upon themselves to implement additional policies and guidance.

What SuDS and Where?

For small house extensions, you don’t need a large budget or space to implement SuDS effectively:

• Permeable Paving: Replace conventional hard surfaces with permeable materials to allow rainwater to soak through rather than running off into a drain.
• Rain Gardens: A shallow, landscaped area that captures and absorbs rainwater from roof downpipes, driveways, or other impervious surfaces.
• Water Butts: A simple and cost-effective way to collect and store rainwater from your roof. Slow-release water butts are specially designed to gradually release stored water after storms.
• Green Roofs: If your extension has a flat or low-pitched roof, consider installing a green roof for stormwater management and energy efficiency benefits.
• Planters: Disconnecting/rerouting a rainwater downpipe to drain into a raised planter can significantly reduce overall runoff.

‘Can’t I Just Put a Soakaway In’?

In some areas, the ground conditions may comprise of clay or another soil with poor permeability, which are not conducive to soakaways. Installing a soakaway into an area with poor soakage characteristics can have the opposite effect as intended, where gardens can become waterlogged and boggy during winter months.

In accordance with British Standards, soakaways must be positioned at least 5m away from any buildings and at least 2.5m from property boundaries and underground utilities. This can be challenging to achieve in small gardens.