A terrace of pastel-painted Regency villas along Greenwich South Street, with a red post box, a bus stop and a brick clock tower behind
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Photo: Tima Miroshnichenko / Pexels

Flood risk assessment · London Borough of Greenwich

Flood risk assessment in Greenwich, from £375 fixed

Royal Greenwich asks for a flood risk assessment not just in Flood Zones 2 and 3 but wherever surface water is 0.3m deep or more, within 100m of recorded sewer flooding or 250m of groundwater flooding. It treats surface water extents as Flood Zone 3, so we check every one of those maps for your address.

Flood risk assessmentfrom £375
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A red clad outbuilding with a white window standing in brown floodwater among bare trees
Flood-resistant materials are specified to a height above the estimated flood level. Photo: Serge Lavoie / Pexels.

What Greenwich Council asks of a flood risk assessment

From the council's Local Validation Requirements List 2025, Flood Risk Assessment (adopted 2025 edition, read 29 October 2026).

  • Greenwich asks for a flood risk assessment for all developments in Flood Zones 2 and 3, including domestic extensions and changes of use to residential, and for sites of 1 hectare or more in Flood Zone 1. (source, checked 29 October 2026)
  • An assessment is also required for all developments where surface water flooding is shown as 0.3m or deeper, within 100m of a sewer flooding incident, or within 250m of a groundwater flooding incident. (source, checked 29 October 2026)
  • Surface water flood extents from the Environment Agency's modelling and Royal Greenwich's SFRA are to be treated the same as Flood Zone 3. (source, checked 29 October 2026)
  • The estimated flood level should use a 1 in 100 river flood or a 1 in 200 tidal flood plus climate change, and where defences are present it should account for the residual risk if they were breached or overtopped. (source, checked 29 October 2026)

What Greenwich flood risk assessment drawings have to show

Greenwich is one of the few councils to put numbers on its local triggers. Before we quote, we check the surface water map for depths of 0.3m or more at your address, and look for recorded sewer flooding within 100m and groundwater flooding within 250m, because any of them brings an assessment even in Flood Zone 1.

For a house near the river, the flood level is taken from the 1 in 200 tidal event with climate change and the residual risk behind the defences. The assessment follows the Environment Agency standing advice for minor extensions, which the council asks applicants to use.

PS2 · at a glance

Greenwich: 624 householder decisions

Greenwich
Approvals, prior approvals included77.1%

481 of 624 granted. London: 85.8%.

Decided within 8 weeks94.7%

469 of 495 applications, prior approvals excluded.

Source: MHCLG PS2, 1 July 2025 to 30 June 2026. Dark tick: London.
Two hands holding a printed floor plan over a desk of drawings, with a pen and notebook beside it
Checking the drawings with you before anything goes to the council. Photo: Tima Miroshnichenko / Pexels.

What it costs in Greenwich

  • Flood risk assessment: from £375.

Flood risk assessment across London · Greenwich planning rules · every price

Flood risk assessment · Greenwich

What happens next in Greenwich

We check your address on every map the council uses, take the flood level with climate change, set the floor level and resilience measures, and mark them on the drawings.

Photo: Helena Jankovičová Kováčová / Pexels

Answers

Greenwich flood risk assessment questions

Does a house extension in Greenwich need a flood risk assessment?
In Flood Zones 2 and 3, yes: Greenwich's Local Validation Requirements List 2025 names domestic extensions specifically. In Flood Zone 1 it is still needed where surface water flooding is shown 0.3m deep or more, or within 100m of a sewer flooding incident or 250m of a groundwater flooding incident.
Why does Greenwich treat surface water risk like Flood Zone 3?
The council's list says surface water flood extents from the Environment Agency's modelling and its own Strategic Flood Risk Assessment are to be treated the same as Flood Zone 3. For a minor extension that means following the Environment Agency standing advice, with floor levels and resilience measures set against the surface water depth.

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