Do You Need A Flood Risk Assessment? The 8 Conditions That Trigger An FRA In England

Checked against the Environment Agency's Flood risk assessments: applying for planning permission (last updated 28 May 2026) and the National Planning Policy Framework (published 17 August 2026). This page covers England; Wales, Scotland and Northern Ireland use different rules.

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When Do You Need A Flood Risk Assessment?

You need a flood risk assessment in England for development, for all development (including minor development and changes of use), in any of the eight situations below. The list is the Environment Agency's, updated on 28 May 2026; if one applies, an FRA must go with the planning application.

The National Planning Policy Framework states the same rule more broadly. In Flood Zone 1, policy F4 requires an FRA for sites of one hectare or more; land identified by the Environment Agency as having critical drainage problems; land identified in a strategic flood risk assessment or the Flood Map for Planning as being at risk of flooding from any source, whether now or in the future. The site's zone, surface water risk and future risk are all shown on the Environment Agency's Flood Map for Planning, and what each zone means is explained in Flood Zones explained.

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Do You Need An FRA For A House Extension?

Yes, you need an FRA for a house extension in Flood Zone 2, 3 or 3b, or where any other trigger applies, but for a minor extension you follow the Environment Agency's shorter standing advice. A minor extension is a household or non-domestic extension with a floor space of no more than 250 square metres.

For a minor extension in Flood Zone 2 or 3, the standing advice asks for:

1. Your site address and a description of the extension.
2. The estimated flood level, taking account of climate change. The design flood is a river flood with a 1 in 100 annual probability plus an allowance for climate change; a tidal flood with a 1 in 200 annual probability plus an allowance for climate change.
3. Finished floor levels. We recommend floor levels are set at least 600 millimetres (mm) above the estimated flood level; You may be able to reduce this to 300mm if there is a high level of certainty about your estimated flood level.
4. Flood resistance and resilience plans if floor levels cannot be raised.
5. Supporting plans and drawings.

A 40 m² rear extension in Flood Zone 3 needs an FRA, but a short one based on this standing advice, not a full modelled study. An extension in Flood Zone 1 with no other trigger needs no FRA. Householder development is also exempt from the sequential test, explained in the sequential test.

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Do You Need An FRA In Flood Zone 1?

You do not need an FRA in Flood Zone 1 unless one of five things applies: the site is one hectare or more, it is in an area with critical drainage problems, the Flood Map for Planning or the council's strategic flood risk assessment shows risk now or in future, or the use raises the vulnerability classification and the site is exposed to other sources of flooding.

If a Flood Zone 1 site will be at increased risk from rivers or the sea during its lifetime, the Environment Agency says to treat the site as if it were in Flood Zone 2 when deciding which advice you need to access. Surface water is easy to miss, because it is not part of the Flood Zone; see surface water flooding.

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What Must A Site-Specific Flood Risk Assessment Contain?

A site-specific flood risk assessment must show the flood risk to the development from all sources, now and with climate change, and how the development will be safe without increasing flood risk elsewhere. The Environment Agency's standing advice lists the core contents.

For development covered by standing advice, the FRA should include: your site address; a description of your development; the estimated flood level for your development, taking into account the impacts of climate change over its lifetime; details of the finished floor levels; details of your flood resistance and resilience plans; any supporting plans and drawings. For vulnerable development it should also assess flood risk from all sources and residual risk from defences being breached or overtopped.

Key technical requirements:

The Environment Agency also publishes a site-specific FRA checklist, and NPPF policy F4 says site-specific assessments should be appropriate to the scale, nature and location of the development.

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Do You Need A Sustainable Drainage Strategy As Well?

You need a sustainable drainage strategy as well as an FRA if your development which could affect drainage on or around the site in an area at risk of flooding such as Flood Zones 2 or 3, or at risk of surface water flooding. The strategy can be part of the FRA or a separate document, and it must follow the national standards for sustainable drainage systems.

What to check:

1. Whether the development could affect drainage on or around the site.
2. Whether the site is at risk from rivers, the sea or surface water.
3. Local requirements from the local planning authority or lead local flood authority.
4. Major development: the NPPF expects sustainable drainage to take account of advice from the lead local flood authority.

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Can You Write Your Own Flood Risk Assessment?

Yes, for a simple, low-risk development such as a house extension, you may be able to write your own flood risk assessment. The Environment Agency states: "You will usually need to pay a flood risk specialist to carry out a FRA for you. An exception to this may be if it is for a simple, low risk development, for example, a house extension. In this case you may be able to do it yourself." For anything larger, a specialist is usually needed.

Cases closest to the Environment Agency's example:

• A minor extension following the standing advice, where the estimated flood level can be obtained from the Environment Agency.
• A change of use covered by standing advice, with no change in floor levels.

Signs the assessment needs a specialist:

• The estimated flood level is not available and must be calculated.
• Hydraulic modelling is needed, or the site is in Flood Zone 3b.
• The sequential or exception test applies.
• Levels must be surveyed relative to Ordnance Datum and no survey exists.

The Environment Agency publishes an FRA template and guidance, and gives pre-application advice. What a specialist typically charges is set out in flood risk assessment cost.

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What Happens If You Submit A Planning Application Without An FRA?

If you submit a planning application without a required FRA, the council can refuse it. The Environment Agency warns: "Your local planning authority (LPA) may refuse your application if you do not include a FRA or if it is not satisfactory."

Other consequences to plan for:

• Delay while the FRA is prepared and the application re-consulted.
• An objection from the Environment Agency where it is a statutory consultee.
• Separate permissions. The Environment Agency tells applicants to check whether the development is within 20 metres of main river or flood defence, and whether they need permission to do work on a river, flood defence or sea defence.

If the site is in Flood Zone 2 or 3, check early whether the sequential test applies, because failing it can lead to refusal even with a good FRA. What different types of building work need is set out in building in a flood zone.

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Sources (Verified 17 Sep 2026)