Sustainable drainage (SuDS) strategy
A sustainable drainage (SuDS) strategy that manages rainfall close to where it lands, using features such as soakaways, permeable paving and green roofs.
About this service
Sustainable drainage, usually called SuDS, means dealing with rain close to where it falls instead of piping it straight into the sewer. Green roofs soak it up, permeable paving lets it through, rain gardens and swales slow it down, and soakaways return it to the ground. Most London boroughs now expect new development to use SuDS wherever practical, and many will not approve drainage that relies only on a tank and a pipe.
Our SuDS strategies look at what is realistic on your site. We consider the ground, the space available, levels, nearby trees and buildings, and how features will be maintained. Then we combine options so they work together. A typical London scheme might pair a green or blue roof on a flat roof with permeable paving at ground level and a small storage tank for heavier storms.
SuDS do more than control flow. Good schemes also clean runoff, add planting and wildlife value and make spaces more pleasant. Councils and the Lead Local Flood Authority increasingly look for these wider benefits. If your scheme is simpler and only needs flows controlled, a surface water drainage strategy may be enough. Our drainage strategy guide explains the difference, and we are happy to advise which your council is likely to want.
When you need it
- Your planning authority requires SuDS
- You want to reduce runoff from a new development
- A lead local flood authority has asked for a SuDS strategy
What's included
- Assessment of SuDS options
- Runoff and storage calculations
- Proposed SuDS layout
- Maintenance considerations
How it works
- Review constraintsWe look at the site layout, ground conditions, levels, trees, basements and sewer records, and any SuDS requirements in the council's local plan or pre-application advice.
- Screen SuDS optionsWe assess each feature against the site, ruling out those that will not work, such as infiltration on low permeability clay, and shortlisting the most practical combination.
- Calculate storageWe calculate runoff and storage for the design storms, including climate change, showing how each feature contributes to meeting the discharge rate the council expects.
- Prepare the layoutWe produce a proposed SuDS layout showing the features, flow routes, overflows and connection, coordinated with the landscaping and building design so that features fit around entrances, levels and structure.
- Set out maintenanceWe explain what each feature needs to keep working and who will be responsible, which councils often require before approving the strategy or discharging conditions.
What you receive
Choosing SuDS that work on a tight London site
On small urban plots, the roof is often the most valuable SuDS space. A blue roof holds water temporarily and releases it slowly, while a green roof absorbs and evaporates a share of the rain. Both add weight, so the roof structure must be designed for the saturated build-up and any stored water. We check this alongside the drainage, which avoids late surprises when the structural design catches up.
Infiltration features need care on clay. Soakaways too close to buildings can soften the ground under foundations, and Building Regulations guidance sets minimum distances from buildings. Where a soakaway is proposed, a BRE 365 infiltration test confirms whether it will drain. Finally, think about maintenance early. A permeable paving surface that is never swept or a flow control that is never cleared can fail within a few years.
Projects that used this service
Frequently asked questions
What are sustainable drainage systems (SuDS)?
SuDS are drainage features that manage rainwater close to where it lands, copying natural drainage instead of sending it straight into a sewer. Examples include green and blue roofs, permeable paving, rain gardens, swales, water butts, soakaways and ponds. They reduce flood risk by slowing flows down and can also improve water quality, landscaping and biodiversity on a site.
Does my planning application need a SuDS strategy?
Major developments in England are expected to include SuDS, and the Lead Local Flood Authority is consulted on them. Many London boroughs also expect SuDS on smaller schemes, such as new houses or several flats, through their local plans. Requirements vary by borough, so check the council's validation list or pre-application advice. We can tell you what is likely to be needed for your site.
Can I use a green roof as part of my SuDS?
Yes, and on many London sites it is one of the best options. Green roofs absorb part of the rainfall and slow the rest, reducing the storage needed elsewhere. The roof structure must be designed for the saturated weight of the soil and planting, so check existing roofs before adding one. Our flat roof guide covers some of the structural points.
Who maintains SuDS after a development is built?
It depends on the scheme. On a single house, the owner usually maintains the features. On larger developments, a management company or the freeholder often takes responsibility, and some features may be adopted by the sewerage company or council. Councils often require a maintenance plan, and our drainage maintenance and management plan sets out who does what and when.