A SuDS statement costs from £295 at Fixed Fee Plans. It is the short drainage document for an extension or a single new home: how much roof and hard surface the scheme adds, where that rainwater will go, and how the design follows the London Plan's drainage hierarchy. Where you also need a flood risk assessment, we write the two together.
For a block of new homes, the fuller drainage strategy is the right document.
Why does a council want a SuDS statement for an extension?
Because in much of London the rain from your new roof goes into the same pipe as the toilets. Hammersmith and Fulham says much of the borough is at risk from sewer and surface water flooding for exactly that reason: foul and surface water drain into a combined sewer, which overwhelms in heavy downpours. Every extension and patio adds to the load, so councils ask small schemes to keep some water on site.
The London Plan backs them. Policy SI 13 says proposals for impermeable surfacing should normally be resisted unless they are unavoidable, including on small sites, and Southwark asks development that must provide sustainable drainage not to increase the area of non-permeable surfaces.
What goes into a SuDS statement?
The areas, the hierarchy and the features. We measure the new roof and paving from the drawings, then work down the London Plan's six-step drainage hierarchy for your plot: use the water, let it soak away, hold it in green features, send it to a watercourse, a surface water sewer, and only last the combined sewer. For a house that usually means water butts, a permeable drive or patio, a rain garden, or a green roof on a flat-roofed extension.
Do councils have their own forms?
Some do. Westminster asks flood-affected proposals for a signed Flood Risk and Sustainable Drainage pro forma, and other councils have their own templates. We complete the council's form where there is one, and write the statement in its order where there is not.
What does it cost with a flood risk assessment?
The statement is from £295 on its own. Written together with a flood risk assessment it shares the same plan measurements and site data, and we quote the pair in writing before you commit. A soakaway needs ground testing and an engineer's design, which is separate, and we tell you if your site needs one.
Frequently asked questions
Do I need a SuDS statement for a rear extension?
Some London councils ask for one with householder applications, especially where the extension adds roof area or paving in a surface water risk area. We check your council's list before quoting.
What counts as a sustainable drainage feature?
Anything that keeps rainwater on site or slows it down: water butts, permeable paving, a rain garden, a soakaway where the ground allows, or a green roof.
Is a SuDS statement the same as a drainage strategy?
No. A drainage strategy covers foul and surface water for new homes and larger schemes. A SuDS statement is the shorter document for an extension or single home.
