A long terrace of brown brick houses above a white stuccoed ground floor on Ponsonby Place in Westminster, with iron railings and no-entry signs
Floor plan drawings, pencil sketches of a house, a scale rule and a protractor spread across a desk
Photo: Tima Miroshnichenko / Pexels

Flood risk assessment · London Borough of Westminster

Flood risk assessment in Westminster, from £375 fixed

Westminster needs a flood risk assessment for any development in Flood Zones 2 and 3 and also anywhere in its own Surface Water Flood Management Zone, with a signed Flood Risk and Sustainable Drainage pro forma. Bedrooms below the modelled Thames breach level are not supported, so we check every floor against it.

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 Westminster Council asks of a flood risk assessment

From the council's City Plan 2019-2040, Policy 39 (Flood risk) (adopted January 2026).

  • Policy 39 requires a site-specific flood risk assessment for developments of 1 hectare or more, all developments in Flood Zones 2 and 3, and all developments within a Surface Water Flood Management Zone. (source, checked 29 October 2026)
  • The supporting text says proposals should be accompanied by a signed Flood Risk and Sustainable Drainage pro forma. (source, checked 29 October 2026)
  • Sleeping accommodation below the modelled breach flood water level, in areas at risk if the Thames Tidal Flood Defences were breached, will not be supported. (source, checked 29 October 2026)
  • Highly Vulnerable uses will not be allowed in Flood Zone 3, and a Flood Warning and Evacuation Plan will generally be required for More Vulnerable uses in areas at risk of tidal breach flooding, especially in the Rapid Inundation Zone. (source, checked 29 October 2026)

What Westminster flood risk assessment drawings have to show

A Westminster assessment checks the Surface Water Flood Management Zone as well as the Environment Agency flood zones, because either one triggers the requirement. We complete the council's Flood Risk and Sustainable Drainage pro forma alongside the assessment and sign it off for you.

Where the house is in the tidal breach area, we set out the modelled breach level against each floor and show that no bedroom sits below it. If the property is in the Rapid Inundation Zone we say so plainly, because the council will generally expect an evacuation plan for homes there.

PS2 · at a glance

Westminster: 366 householder decisions

Westminster
Approvals, prior approvals included82%

300 of 366 granted. London: 85.8%.

Decided within 8 weeks66.1%

123 of 186 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 Westminster

  • Flood risk assessment: from £375.

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

Flood risk assessment · Westminster

What happens next in Westminster

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

Westminster flood risk assessment questions

What is a Surface Water Flood Management Zone in Westminster?
An area the council has identified as at risk from surface water flooding in its Strategic Flood Risk Assessment. Policy 39 of the City Plan says every development within one needs a site-specific flood risk assessment, even outside the Environment Agency's Flood Zones 2 and 3. We check your address against both before we quote.
Does Westminster need a form with the flood risk assessment?
Yes. The supporting text to Policy 39 says proposals should be accompanied by a signed Flood Risk and Sustainable Drainage pro forma, and that the council aligns its assessment requirements with its Strategic Flood Risk Assessment. We fill the pro forma in with the assessment so the two match.
Can I put a bedroom in a Westminster basement near the Thames?
Not below the modelled breach flood level. The City Plan says sleeping accommodation below that level, in areas that would flood if the Thames Tidal Flood Defences were breached, will not be supported. Highly Vulnerable uses, which include basement dwellings, are not allowed in Flood Zone 3.

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Measured surveyWithin five working days
£150
02
Existing drawingsThe building as it stands
£175
03
Proposed drawingsYour scheme, revised until right
£225
04
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£125
05
Submission and agent servicePortal submission, queries handled
£120
Total, planning application£795
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