"Do I need a flood risk assessment?" has a precise answer in national guidance — it depends on your flood zone, your site's size, and a handful of specific triggers. This checker looks up your zone live from the Environment Agency's planning dataset and applies the rules, telling you not just whether but why.
Check if you need an FRA
The checker needs JavaScript. The rules are in the GOV.UK guidance.
The five triggers
- Flood Zone 2 or 3 — an FRA is required for any development, whatever its size.
- Flood Zone 1 over 1 hectare — required, mainly to deal with surface water and drainage.
- Within 20 m of a main river — required, and works may also need an environmental permit.
- Known drainage or surface-water problems — councils increasingly require an FRA on Zone 1 sites sitting on mapped flow paths or in critical drainage areas.
- Change of use to a more vulnerable category — for example commercial to residential in a flood risk area.
Zones only cover rivers and the sea — surface water, which now affects 4.6 million properties in England, is checked separately on the government's long-term risk service.
What an FRA actually contains
A proportionate, site-specific FRA identifies the sources of risk, states finished floor levels and resilience measures against Environment Agency standing advice, supports the sequential test where it applies (see can I build in a flood zone?), and sets a drainage strategy — usually SuDS to CIRIA C753. For small schemes this is a document, not a drama: ours takes minutes.
How Fortress Associates can help
If any trigger applies — or you would rather close the question for good — our automated flood risk assessment is free and ready in minutes: live Environment Agency data, flood-zone screening, surface water, sequential and exception test support and a CIRIA C753 SuDS strategy, following the EA's March 2025 template, for householder extensions, new dwellings and small schemes across England. Check your zone first with the flood zone checker, or see every tool at /free-tools.
Sources & further reading
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