A flood risk assessment (FRA) is a report submitted with a planning application. It explains the flood risk to the site, how the development will be kept safe, and how it will avoid making flooding worse for anyone else. Without one, when it’s required, the council can refuse to validate or approve your application.
When you need one
In England you need a flood risk assessment for a planning application if the site is:
- in Flood Zone 2 or 3 – this includes householder extensions and minor development;
- in Flood Zone 1 and 1 hectare or more in size;
- in Flood Zone 1 and less than 1 hectare, but in an area the Environment Agency has told the council has critical drainage problems;
- in Flood Zone 1 and at risk from other sources of flooding, or at future flood risk, where you’re changing to a more vulnerable use – for example, from a shop to a home.
Not sure which zone you’re in? Check the postcode for free, then confirm on the Flood Map for Planning, which can also produce the flood map extract councils ask for.
Extensions and standing advice
For many small extensions and alterations, you don’t need a consultant. The Environment Agency publishes standing advice for minor extensions, and your assessment can be a short statement showing you’ve followed it. That generally means:
- setting floor levels no lower than the existing ones, or 300mm above the estimated flood level;
- using flood resilient and resistant construction where floor levels can’t be raised;
- explaining how water will drain from the extension without increasing flood risk elsewhere.
Read our guide to extending a home in Flood Zones 2 and 3 for more detail.
Bigger projects
New homes, conversions and larger schemes usually need a site-specific FRA by a flood risk consultant. It will use flood levels for the site – which you can request from the Environment Agency – and may include modelling, a drainage strategy, and evidence for the ‘sequential test’ and ‘exception test’ that new development in flood risk areas has to pass.
Permitted development
If your project doesn’t need planning permission because it’s permitted development, there’s no planning application, so no FRA is required. It still makes sense to follow the same principles – it’s your home that would flood.
Check the government guidance on flood risk assessments or ask your council’s planning team if you’re unsure what yours needs.
Last reviewed November 2026. This guide is general information about England, not legal, financial or insurance advice. Check the Environment Agency’s own services and speak to a professional before making decisions about a specific property.
