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Find out if you need to follow standing advice when completing a flood risk assessment and what to do.

Local planning authorities (LPAs) should use flood risk standing advice for local planning authorities to check when to consult the Environment Agency or use standing advice.

Planning applicants and LPAs should use this guide to make sure flood risk assessments (FRAs):

If your site is in flood zone 1 but your LPA’s strategic flood risk assessment (SFRA) shows it will be at risk of flooding from rivers or the sea in future, you should:

Follow standing advice for vulnerable developments for developments (including change of use) in flood zone 2 and have a vulnerability classification of:

Use the advice for minor extensions to complete an assessment for a minor extension in flood zone 2 or 3. A minor extension is a household or non-domestic extension with a floor space of no more than 250 square metres.

If your development is not covered by the standing advice in this guide:

LPAs will also consult the Environment Agency as set out in the flood risk assessments: standing advice for local planning authorities guidance.

A FRA is required for all development:

Before starting your FRA you should do the following research:

You should also check the LPA’s SFRA to find out if the development is:

In addition you need to check the Environment Agency’s flood map to find if your development is within:

Before you start a FRA, check if your development needs to satisfy the sequential test. The sequential test steers development to areas with the lowest flood risk. It compares your proposed site with other available sites to show which one has the lowest flood risk. The LPA may refuse planning permission if other, lower risk sites are identified. You need to justify and provide evidence of the search area you used. Contact your LPA early to discuss whether your development can satisfy the sequential test.

If the sequential test is satisfied you need to check if the exception test also needs doing. If it does, you need to satisfy both elements of the exception test before the LPA can permit the development.

You may need a separate permit or consent if the development:

Check if you need permission to do work on a river, flood defence or sea defence. Do this as soon as possible to make sure you can get the necessary permissions.

Flood risk permits or consents are often needed as well as planning permission. Getting planning permission does not guarantee you’ll also get a flood risk permit or consent.

For all developments covered by this standing advice, your FRA should include:

The estimated flood level is the depth of flooding anticipated on your development site in a:

If flood defences are present, the estimated flood level should account for the residual flood risk if they breached or overtopped. You may be able to get the estimated flood level from the Environment Agency or your LPA. If not, you’ll need a flood risk specialist to calculate this for you.

You need to provide a plan showing the finished floor levels and the estimated flood levels.

State in your assessment all levels in relation to Ordnance Datum (the height above average sea level). You may be able to get this information from the Ordnance Survey. If not, you’ll need to get a land survey carried out by a qualified surveyor.

Make sure the floor levels are either no lower than existing floor levels or 300 millimetres (mm) above the estimated flood level. You will also need to use flood resistant materials up to at least 300mm above the estimated flood level.

Flood water can put pressure on buildings, causing structural issues. If your design aims to keep out a depth of more than 600mm of water, you should get advice from a structural engineer.

Standards for the installation and retrofit of resistance measures are available in British Standard 851188-1:2019+A1:2021.

If you cannot raise the floor levels in this way, you will also need to include extra flood resistance and resilience measures. These measures should protect the property to at least 300mm above the estimated flood level.

Make sure your flood resilience plans follow the guidance in the Construction Industry Research and Information Association (CIRIA) Property Flood Resilience Code of Practice.

Standards for materials and design approaches that will speed the recovery of buildings after flooding are available in British Standard 85500:2015.

Standards for dealing with and preventing water from surrounding ground entering below ground structures such as basements are available in British Standard 8102:2009.

Your plans also need to show how you’re going to ensure the development is not flooded by surface water or groundwater. This could be by:

Check with the LPA to see if your minor extension is in an area with increased flood risk because of multiple minor extensions in the area. If it is, you need to include an assessment of the off-site flood risk.

Check table 3 of the planning practice guidance if your proposed minor extension is in flood zone 3b (functional floodplain). It states that development should not be permitted in flood zone 3b if its vulnerability classification is:

For all relevant vulnerable developments, you should follow the advice for:

You need to provide the:

Finished floor levels should be a minimum of whichever is higher of 300mm above the:

You should also use construction materials that have low permeability up to at least the same height as finished floor levels.

Standards for the installation and retrofit of resistance measures are available in British Standard 851188-1:2019+A1:2021. State in your assessment all levels in relation to Ordnance Datum (also known as height above average sea level). You may be able to get this information from the Ordnance Survey. If not, you’ll need to get a land survey carried out by a qualified surveyor.

If you cannot raise floor levels to meet the minimum requirement, you will need to:

When considering the height of floor levels, you should also consider any additional requirements set out in the SFRA. Flood water can put pressure on buildings causing structural issues. If your design aims to keep out a depth of more than 600mm of water, you should get advice from a structural engineer. They will need to check the design is safe.

Follow the guidance in this section for developments in flood risk areas where you cannot raise the finished floor levels to the required height. You should design buildings to exclude flood water where possible and to speed recovery in case water gets in.

Make sure your flood resilience plans for the development follow the guidance in the CIRIA Property Flood Resilience Code of Practice. Please note that the code of practice uses the term ‘recovery measures’. In this guide we use ‘resilience measures’.

Flooding can affect the structural stability of buildings. If your building design would exclude more than 600mm of flood water, you should get advice from a structural engineer. They will need to check the design is safe. Only use resistance measures that will not cause structural stability issues during flooding. If it is not possible to safely exclude the estimated flood level, exclude it to the structural limit then allow additional water to flow through the property.

The design should be appropriately flood resistant and resilient by:

Standards for the installation and retrofit of resistance measures are in British Standard 851188-1:2019+A1:2021.

Standards for speeding the recovery of buildings after a flood are in British Standard 85500:2015.

Standards for dealing with and preventing water from the surrounding ground entering below ground structures such as basements are in British Standard 8102:2009.

You will also need to comply with relevant Building Regulations in Part P. They set minimum and maximum heights for certain electrical infrastructure.

Temporary or demountable flood barriers are not appropriate for new buildings. Only consider them for existing buildings when:

If proposals involve the development of buildings constructed before 1919, refer to Flooding and Historic Buildings guidance produced by Historic England.

You need to provide details of your emergency escape plans for any parts of a building that are below the estimated flood level. Follow the Flood Risk Emergency Plans for New Development guidance.

Make sure your plans show:

You will also need to comply with relevant Building Regulations in Part B. They require you to provide suitable access for the fire service.

You should use SuDS for all:

If you do not include SuDS in these circumstances, you need to provide the LPA with clear evidence of why their use would be inappropriate.

In major developments SuDS should also provide multifunctional benefits where possible.

You should include information about SuDS in a sustainable drainage strategy or as part of your FRA. See section 6: surface water management of the site-specific flood risk assessment: checklist for the information you need to include.

Your plans for the management of surface water need to meet any requirements set out in your local authority’s:

They also need to meet the requirements of the planning practice guidance and the approved building regulations Part H: drainage and waste disposal. Read section H3 rainwater drainage.

Refer to the non-statutory technical standards for guidance on the design, maintenance and operation of SuDS. Further guidance on how to design SuDS to maximise their benefits is in the CIRIA Suds Manual.

You can follow Water UK’s Design and Construction Guidance to design and construct SuDS. This will ensure they qualify for adoption by the relevant water and sewerage company.

You need planning permission to surface more than 5 square metres of a front garden using a material that cannot absorb water.

Submit your completed FRA with your planning application to your LPA.

The LPA will review your FRA and tell you if it’s satisfactory. Planning applications that do not have a satisfactory FRA may be refused.

Clarity improved to reflect the latest National Planning Policy Framework, historic buildings guidance, the CIRIA Property Flood Resilience Code of Practice and relevant British Standards and Building Regulations. Improved links to strategic flood risk assessments. Greater clarity on the need for flood risk assessments, sustainable drainage information and sequential and exception test information. Highlight the need to check the compatibility of the proposed use with the flood zone. Clearer approach to flood risk mitigation. Highlighting that some developments may also need a flood risk activity permit.

Guidance reviewed and no changes made.

Clarity improved and links updated. Clarified status of advice for minor extensions and advice on climate change. Added ‘extra resistance and resilience measures’ section from 'Flood risk standing advice for local planning authorities' guide. Included advice for areas of flood zone 1 that will be at future risk.

Changed URL for Find out what flood zone your development is in, to the new Flood Map for Planning service. Changed URL for Check if your development is within 20 metres (m) of a main river, to the Main River map

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