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

• contain the correct information
• follow the standing advice

If your site is in Flood Zone 1 but the LPA鈥檚 strategic flood risk assessment (SFRA) or the show it will be at increased risk of flooding from rivers or the sea in future, you should:

• complete a flood risk assessment (FRA)
• apply this guidance as if the site were in Flood Zone 2

Check if your site will be at increased risk of flooding from rivers or sea in future. Do this by referring to the LPA鈥檚 strategic flood risk assessment (SFRA).

When to follow standing advice

Follow standing advice for vulnerable developments for developments (including change of use) in Flood Zone 2 that have a vulnerability classification of:

• 鈥榤ore vulnerable鈥� - except for landfills, waste facility sites, caravan or camping sites where the Environment Agency should be consulted
• 鈥榣ess vulnerable鈥� - except for waste treatment sites, mineral processing sites, water treatment plants and sewage treatment plants where the Environment Agency should be consulted
• 鈥榳ater compatible鈥�

You should 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 householder or non-domestic extension with a floor space of no more than 250 square metres.

Also follow local flood risk standing advice for development (including change of use) if your site is in an . These are currently only designated in and . Contact the LPA for a copy of the local standing advice.

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

• read flood risk assessment for planning applications and the flood risk assessment check-list
• consider asking the Environment Agency for pre-application advice on flood risk

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

Advice for minor extensions

For all relevant minor extensions (see when to follow standing advice), you should follow the standing advice for:听

• what to include in your FRA听
• floor levels听
• extra flood resistance and resilience measures听
• other permissions or consents

What to include in your FRA

驰辞耻谤鈥�FRA鈥痵hould be:听

• appropriate to the scale, nature and location of the development听
• proportionate to the degree of flood risk听

Your FRA should appraise the suitability of the flood risk datasets it has used. This should take account of:听

• when the dataset was produced听
• why the dataset was produced听
• the limitations of the dataset

Your FRA should contain the information set out in the site-specific flood risk assessment check-list.听听

For all development covered by this standing advice, your鈥�FRA鈥痵hould include:听

• your site address听
• a description of your development听
• the estimated flood level for your development, taking into account the impacts of climate change over its lifetime听
• details of the finished floor levels听
• details of your flood resistance and resilience plans听
• any supporting plans and drawings听
• any other information the relevant standing advice tells you to include听

The estimated flood level is the depth of flooding anticipated on your development site.

For a river flood, this is a 1 in 100 annual probability event plus an allowance for climate change.听For a tidal flood, this is a 1 in 200 annual probability event plus an allowance for climate change.

You may be able to request the estimated flood level and information about residual risks through the Environment Agency鈥檚 . If not, you will need a flood risk specialist to calculate this for you.听

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

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

Check table 2 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:听

• 鈥榟ighly vulnerable鈥櫶�
• 鈥榤ore vulnerable鈥櫶�
• 鈥榣ess vulnerable鈥�

Floor levels

We recommend floor levels are set at least 600 millimetres (mm) above the estimated flood level. You will also need to use flood resistant materials up to at least 600mm above the estimated flood level.听

You may be able to reduce this to 300mm if there is a high level of certainty about your estimated flood level. If there is a particularly high level of uncertainty it may need to be increased.听

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.听

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 600mm above the estimated flood level.听

Your plans also need to show how you are going to make sure the development is not flooded by surface water or groundwater.

This could be by:听

• diverting water away from buildings but safely managing it within the site
• raising floor levels above the estimated flood depths of surface and groundwater flooding

Extra flood resistance and resilience measures

Follow the guidance in this section where you cannot raise the finished floor levels to the required height. Your building design should:

• prioritise excluding flood water where possible
• speed recovery in case water gets in

Make sure your flood resilience plans follow the guidance in the .听

Standards are available for:听

• the installation and retrofit of resistance measures - 听
• speeding the recovery of buildings after a flood - 听
• dealing with and preventing water from the surrounding ground entering below ground structures such as basements -

Other permissions or consents

You may need a separate permit or consent if the development or any associated works such as site preparation or construction:听

• is within 20 metres of a main river (including culverted main rivers), a flood defence or flow control structure听
• directly affect a watercourse that is not a main river听
• involve activity in the floodplain of a main river which could divert or obstruct floodwaters, damage any river control works or affect drainage, and potential impacts are not controlled by a planning permission听
• are covered by regional flood defence and land drainage byelaws, where these are applicable听

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.听

You can check if your development activity and location are covered by regional flood defence and land drainage byelaws by referring to this statutory guidance.听

If there is a watercourse (including culverted watercourses) on or next to your site, read owning a watercourse and .鈥� They will help you understand your responsibilities and the rules you need to follow. A culvert is an underground structure that water can flow through.听

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

Standing advice for vulnerable developments

For all relevant vulnerable development (see when to follow standing advice), you should follow the standing advice for:听

• what to include in your FRA听
• sequential and exception tests听
• floor levels听
• extra flood resistance and resilience measures听
• access and escape听
• surface water management听
• other permissions or consents

What to include in your FRA

Your FRA鈥痵hould be:听

• appropriate to the scale, nature and location of the development听
• proportionate to the degree of flood risk听

Your FRA should appraise the suitability of the flood risk datasets it has used. This should take account of:听

• when the dataset was produced听
• why the dataset was produced听
• the limitations of the dataset

Your FRA should contain the information set out in the site-specific flood risk assessment check-list.听听

For all development covered by this standing advice, your鈥�FRA鈥痵hould include:听

• your site address听
• a description of your development听
• an assessment of the flood risk from all sources of flooding for your development, plus an allowance for climate change听
• the estimated flood level for your development, taking into account the impacts of climate change over its lifetime听
• an assessment of the residual risks resulting from the breach or overtopping of any flood defences听
• details of the finished floor levels听
• details of your flood resistance and resilience plans听
• any supporting plans and drawings听
• any other information the relevant standing advice tells you to include听

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

• river flood with a 1 in 100 annual probability plus an allowance for climate change听
• tidal flood with a 1 in 200 annual probability plus an allowance for climate change听

You may be able to request the estimated flood level and residual risk information from the Environment Agency using the . If not, you will need a flood risk specialist to calculate this for you.听

You should follow guidance in Using modelling for flood risk assessments to check:听

• when you may need to use modelling听听
• what standards to follow听
• how to get modelling advice听
• what information you need to provide

Sequential and exception tests

Before you start a鈥�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鈥�LPA鈥痬ay refuse planning permission if other, lower risk sites are identified.听

When the sequential test is needed

A sequential test is required for major and non-major development (refer to鈥�check the development class if any proposed building, access and escape route, land-raising or other vulnerable element will be:听

• in Flood Zone 2 or 3
• in Flood Zone 3b and your development is not incompatible听
• within Flood Zone 1 and the shows it is at increased risk of flooding from rivers or sea during its lifetime听
• with Flood Zone 1 and the shows it is at risk of flooding from surface water
• in Flood Zone 1 and the听LPA鈥檚鈥�SFRA鈥痵hows it will be at increased risk of flooding during its lifetime
• subject to sources of flooding other than rivers or sea

A development is not exempt from the sequential test just because a听FRA听shows it can be made safe throughout its lifetime without increasing risk elsewhere. See听what is the aim of the sequential approach?.

When development is exempt from the sequential test

Development is exempt from the sequential test if it is a:听

• householder development like residential extensions, conservatories or loft conversions
• small non-domestic extensions with a footprint of less than 250 square metres
• change of use (except changes of use to a caravan, camping or chalet site, or to a mobile home or park home site)

Development is also exempt from the sequential test if it is a development on a site allocated in the development plan through the sequential test and:听

• the proposal is consistent with site鈥檚 allocated use
• there have been no significant changes to the known level of flood risk to the site, now or in the future, which would have affected the outcome of the test

You may not need a sequential test if development can be laid out so that only elements such as public open space, biodiversity and amenity areas are located in areas at risk of any source of current or future flooding.

How to apply the sequential test

You should speak to the LPA early to discuss the sequential test and to determine an appropriate area of search for the test. The鈥�LPA鈥痵hould consider whether the test is passed, with reference to the information it holds on land availability.听

Also include information with your application to identify any other 鈥榬easonably available鈥� sites not already identified by the鈥�LPA within the area of search. This should include sites such as those currently available on the open market. The鈥�LPA鈥痬ay also require you to check on the current status of alternative sites to determine if they can be considered 鈥榬easonably available鈥�. Refer to guidance on Applying the sequential test to individual planning applications. Speak to the鈥�LPA鈥痶o find out what further information may be needed on the sequential test.听

If the sequential test is satisfied you need to check if the exception test also needs doing.

When the exception test is needed

The exception test is needed for development with a vulnerability classification of:听

• 鈥榟ighly vulnerable鈥� in Flood Zone 2听
• 鈥榤ore vulnerable鈥� in Flood Zone 3a听
• 鈥榚ssential infrastructure鈥� in Flood Zone 3a or 3b听

If it does, you need to satisfy both elements of the exception test before the鈥�LPA鈥痗an permit the development.

Floor levels

You need to provide the:听

• average ground level of your site听
• ground level of the access road(s) next to your building听
• finished floor level of the lowest room in your building听

Finished floor levels should be a minimum of whichever is higher of 600mm above the:听

• average ground level of the site听
• adjacent road level to the building听
• estimated river or sea flood level听

Where there is a high level of certainty about your estimated flood level, it may be appropriate to reduce this to 300mm. If there is a particularly high level of uncertainty it may need to be increased.听

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

Your plans also need to show how you are going to make sure the development is not flooded by surface water or groundwater. This could be by:听

• diverting water away from buildings but safely managing it within the site听
• raising floor levels above the estimated flood depths of surface and groundwater flooding听

Standards for the installation and retrofit of resistance measures are available in .听听

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 . If not, you will need to get a land survey carried out by a qualified surveyor.听

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

• raise them as much as possible听
• consider moving vulnerable uses to upper floors听
• include extra flood resistance and resilience measures听

Internal flooding of new vulnerable development like residential dwellings is unlikely to be considered appropriately flood resistant and resilient.听

When considering the height of floor levels, you should also consider any additional requirements set out in the鈥�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.

Extra flood resistance and resilience measures

Follow the guidance in this section where you cannot raise the finished floor levels to the required height. Your building design should:

• prioritise excluding flood water where possible
• speed recovery in case water gets in

Make sure your flood resilience plans for the development follow the guidance in the . Note that the code of practice uses the term 鈥榬ecovery measures鈥�. In this guide we use 鈥榬esilience measures鈥�.听

Only use resistance measures that will not cause structural stability issues during flooding. It may not be possible to safely exclude the full estimated flood level. If this is the case, you will need to 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:听

• using flood resistant materials that have low permeability to at least 600mm above the estimated flood level听
• making sure any doors, windows or other openings are flood resistant to at least 600mm above the estimated flood level听
• using flood resilient materials (for example lime plaster) to at least 600mm above the estimated flood level听
• raising all sensitive electrical equipment, wiring and sockets to at least 600mm above the estimated flood level听
• making it easy for water to drain away after flooding such as installing a sump and a pump听
• making sure there is access to all spaces to enable drying and cleaning听
• making sure that soil pipes are protected from back-flow such as by using non-return valves听

Standards are available for:听

• the installation and retrofit of resistance measures - 听
• speeding the recovery of buildings after a flood - 听
• dealing with and preventing water from the surrounding ground entering below ground structures such as basements -

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

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

• there is clear evidence that it would be inappropriate to raise floor levels and include passive resistance measures听
• an appropriate flood warning or other appropriate trigger is available听

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

Access and escape

You need to provide details of your emergency access and escape plans if any part of your development is below the estimated flood level. This includes access and escape routes. Follow the .听

Make sure your plans show:听

• a safe route of access and escape which is set above the estimated flood level and connects the site to an area away from current or future flood risk听
• that any single storey buildings or ground floors without access to upper floors can access a safe refuge above the estimated flood level听
• that any basement rooms have clear internal access - for example a staircase to an upper floor above the estimated flood level听
• how the development could be evacuated before an extreme flood 鈥� this is an event with a 0.1% annual probability of flooding plus an allowance for climate change

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

Surface water management

You need to include a sustainable drainage strategy if your application is for development:听

• which could affect drainage on or around the site听
• in an area at risk of flooding听

If sustainable drainage systems (SuDS)鈥痑re required but are not included in the development, provide the鈥�LPA鈥痺ith evidence of why SuDS would be inappropriate.听

Even where the National Planning Policy Framework does not require SuDS, we recommend their consideration on all development types, including changes of use, wherever appropriate.听

Wherever possible, your SuDS will need to provide multifunctional benefits for:听

• water quantity听
• water quality听
• biodiversity听听
• amenity听听

You should include all the information set out in Sustainable Drainage Systems. You can put it in a separate document or in the鈥�FRA.听

To ensure an acceptable standard of operation for the lifetime of the development, SuDS for major development will need to have:听

• appropriate minimum operational standards听听
• maintenance arrangements

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

• local plan or supplementary planning documents听
• local flood risk management strategy听
• surface water management plan where available听
• SuDS鈥痝uidance where available听
• SFRA听

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.听

Refer to the non-statutory technical standards for guidance on the design, maintenance and operation of鈥�SuDS. Further guidance on how to design鈥�SuDS鈥痶o maximise their benefits is in the .听

You can follow to design and construct鈥�SuDS. This should make sure they qualify for adoption by the relevant water and sewerage company.听

You need planning permission to surface more than 5 square metres of a front garden using a non-porous material.

Other permissions or consents

You may need a separate permit or consent if the development or any associated works such as site preparation or construction:听

• is within 20 metres of a main river (including culverted main rivers), a flood defence or flow control structure听
• directly affect a watercourse that is not a main river听
• involve activity in the floodplain of a main river which could divert or obstruct floodwaters, damage any river control works or affect drainage, and potential impacts are not controlled by a planning permission听
• are covered by regional flood defence and land drainage byelaws, where these are applicable听

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.听

You can check if your development activity and location are covered by regional flood defence and land drainage byelaws by referring to this statutory guidance.听

If there is a watercourse (including culverted watercourses) on or next to your site, read owning a watercourse and . They will help you understand your responsibilities and the rules you need to follow. A culvert is an underground structure that water can flow through.听

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

Submit your flood risk assessment

You should submit your completed FRA with your planning application to your LPA.听

The LPA will review your FRA and tell you if it is satisfactory. Planning applications that do not have a satisfactory鈥�FRA鈥痬ay be refused.