Flood risk zone
What is a flood risk zone, and does it affect my extension?
What is a flood risk zone, and does it affect my extension?
Flood risk zones are Environment Agency areas describing the probability of flooding (Zones 1, 2 and 3). Development in the higher zones needs a flood risk assessment, and some types face sequential and exception tests. For most householder extensions the main effect is a requirement to assess and manage flood risk.
What flood risk zone means
The zones reflect the chance of flooding from rivers and the sea, before flood defences are taken into account.
Higher zones do not ban development, but they raise the evidence required and can steer where and how you build.
What it means for your project
In Zone 2 or 3, expect to submit a flood risk assessment and to design for flood resilience — raised floor levels, resistant materials, safe access.
Surface water drainage matters too: hard surfaces and basements change how a site handles water, which the council will ask about.
Flood risk zone is published as the “Flood risk zone” dataset on the national planning data index. A Planning Policy report reads it live for your exact address.
Where flood risk zone matters most
Does flood risk zone apply at your address?
A Planning Policy report applies the official rules to your exact property: the designations on your address, the policies that bear on your project — quoted verbatim — and what decided applications nearby show. Generated in minutes.