Costing the sequential and exception tests for flooding
A flood sequential test is priced by its search area, not its page count. Here is what drives the cost, where the availability evidence comes from, and how to avoid paying for the work twice.
The sequential test cost is set almost entirely by one decision you do not control: how wide the authority says the area of search has to be. A test across a single parish is a day of desk work. The same test across a district with a live housing land supply argument can run to weeks, because every reasonably available site in that area has to be identified, assessed and ruled out on the evidence rather than on assertion.
So the useful question is not what the test costs. It is what drives the cost, and which of those drivers you can settle before anyone starts work.
What the test has to prove
National policy steers development away from areas at highest flood risk. The Sequential Test (Flood Risk) demonstrates that there are no reasonably available sites at a lower risk of flooding that could accommodate the proposed development. Not that your site is good. That there is nowhere better.
The Planning Practice Guidance on flood risk and coastal change sets out the method, including the sequential approach within a site, which is often forgotten. Even where the test is passed at the site selection stage, the most vulnerable uses have to sit in the parts of the site at lowest risk, with parking, landscaping and ancillary space taking the rest. An inspector will ask about internal layout before asking about alternative sites.
Three ingredients make the document defensible. A clear statement of the development's flood risk vulnerability classification, an agreed area of search, and a site by site assessment that deals with availability, suitability and whether each candidate could accommodate the development proposed.
The search area decides the budget
The guidance says the area over which the test is applied depends on the nature of the proposal and should be agreed with the local planning authority. In practice there are three common outcomes, and the cost difference between them is large.
| Agreed search area | What the evidence has to cover | Effort |
|---|---|---|
| The application site only | Internal layout and vulnerability zoning | Lowest, part of the flood risk assessment |
| A settlement or parish | Allocated and unallocated sites in that settlement, availability checks | Moderate |
| The whole authority area | Local plan allocations, housing and employment land availability studies, brownfield register, marketed sites | Highest, plus rework risk |
| A functional catchment or wider | As above across multiple authorities | Highest, often needs a strategic argument |
Agree it in writing. A pre-application response that names the search area is worth more than any amount of later argument, and most authorities publish a pre-application charging schedule so the cost of getting that answer is knowable in advance. Where the authority declines to confirm, state your assumed area and your reasons in the report itself, so a refusal has to engage with the assumption rather than ignore it.
Where availability evidence comes from
Most of the work is collecting the site list, and the sources are public. The adopted local plan and its site allocations, the authority's housing and economic land availability assessment, the brownfield land register, the Strategic Flood Risk Assessment prepared to support the local plan, and the Environment Agency Flood Map for Planning for the zone of every candidate.
Availability is where consultants differ most in how much they charge, because it is the part that cannot be desk-based alone. A site allocated for housing is not available if it has an extant permission being built out, if it is in multiple ownership with no agreement, or if it has been marketed without interest. Evidencing that properly means land registry checks, agent enquiries and a written record of each, and the number of candidate sites multiplies all of it.
Keep the test honest about suitability too. A 40 unit scheme cannot be accommodated on a 0.2 hectare town centre plot, and saying so with a capacity sketch is faster than arguing the point later. Where the reader needs the flood evidence itself rather than the site selection, that sits in the Flood Risk Assessment.
When the exception test is added
The Exception Test (Flood Risk) applies where the sequential test has been passed but the development remains in a higher risk location and its vulnerability classification requires it. It has two limbs, and both have to be satisfied.
The first asks whether the development would deliver wider sustainability benefits to the community that outweigh the flood risk. The second asks whether the development will be safe for its lifetime, without increasing flood risk elsewhere and, where possible, reducing flood risk overall. Check the exact wording against the current Framework and the current guidance before you draft, because this text has been amended more than once in recent editions and older precedents quote language that has gone.
The second limb is the expensive one. Safety for the lifetime of the development means modelled flood levels with the appropriate climate change allowance, finished floor levels set above them, dry or safe access and egress demonstrated on a plan, flood resilient construction where levels cannot be achieved, and a flood warning and evacuation plan agreed in principle with the lead local flood authority. Hydraulic modelling, where the Environment Agency's published model does not cover your reach in enough detail, is a separate commission with its own fee.
Rework, and how to avoid paying for it twice
The standard failure runs like this. The test is prepared across the parish, the officer consults the Environment Agency, the Agency or the authority says the search should have covered the district, and the whole site assessment is redone. That second pass costs close to the first.
Four habits reduce it. Ask the question at pre-application and get the answer in writing. Write the method section so it states the search area, the date of each data source and the vulnerability classification applied. Build the site schedule as a table that can be extended rather than as prose. And where you suspect the authority will push the boundary outwards, price the wider area as an option in the fee proposal rather than as a variation.
Published fees you can actually budget
Two costs here are published and indexed, so put them in the appraisal with a date. Planning application fees are set by national regulations and have been subject to annual indexation, with the current figures on the gov.uk fees page, and the approach to that uplift is covered in more detail alongside how application fees are set by floorspace and site area. Pre-application charges are set by each authority and published on its website.
Consultant fees for the test itself are not published anywhere and vary with the search area, so ask for a fee scoped to a stated number of candidate sites rather than a lump sum. PlanScope's own pricing is published and fixed: one free report, £50 per report, or £150 per month for the Professional tier, and you can see the detail on the pricing page.
Scoping the commission before you appoint
Write the brief in this order and the quotes you get back will be comparable. State the development and its vulnerability classification. State the search area and attach the evidence that it was agreed. List the data sources the consultant is expected to interrogate. Say whether hydraulic modelling is in scope or excluded. And set out who prepares the flood warning and evacuation plan, because that frequently falls between the flood risk consultant and the applicant.
Illustrative example: for a 12 unit scheme in Flood Zone 3a where the authority agrees a settlement-wide search, the realistic package is a site schedule of perhaps fifteen candidates, a short availability note on each, an internal sequential layout drawing, and an exception test built on the Agency's existing model outputs. Widen the search to the whole district and the candidate list, not the method, is what expands.
No formal competence requirement attaches to the author of a sequential test, which is why the quality varies so much. Draft the narrative documents with PlanScope and send the flood work for review by a suitably qualified consultant before it goes anywhere near a validation officer. This is general guidance, not legal advice, so check the position with your local planning authority or a qualified professional before relying on it.
PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. For specialist technical reports, qualified professional input may be required.
Frequently asked questions
Who decides how wide the sequential test search area should be?
The local planning authority, in discussion with the applicant. National guidance says the area over which the test is applied depends on the nature of the proposal and should be agreed with the authority. Get that agreement at pre-application and in writing, because a later disagreement means redoing the site assessment across a wider area.
Does the sequential test apply within a single site?
Yes. The sequential approach within a site requires the most vulnerable parts of the development to be placed in the areas at lowest risk, with parking, access and landscaping taking the higher risk land. Inspectors often ask about internal layout before alternative sites, so include a zoning drawing even where the site-wide test is straightforward.
When is the exception test needed as well?
Where the sequential test has been passed but the development still sits in a higher risk location and its flood risk vulnerability classification requires it. Both limbs must be satisfied, covering wider sustainability benefits to the community and safety for the lifetime of the development. Check the current Framework wording, which has changed between recent editions.
What makes the exception test expensive?
The safety limb. Demonstrating safety for the lifetime of the development usually means modelled flood levels with the appropriate climate change allowance, finished floor levels set above them, safe access and egress shown on a plan, resilient construction details and an evacuation plan agreed with the lead local flood authority. Bespoke hydraulic modelling is a separate commission.
Does the author of a sequential test need a formal qualification?
No formal licence or competence requirement attaches to the sequential test, which is one reason the quality of submitted tests varies so widely. What the authority assesses is the defensibility of the search area, the completeness of the site list and the evidence behind each availability conclusion, so get the work reviewed by a flood risk consultant before submission.
Where can I find the published costs around a flood application?
Planning application fees are set by national regulations and published on gov.uk, and have been subject to annual indexation. Pre-application charges are published by each local planning authority on its own website. Consultant fees for the test itself are not published, so ask for a quote scoped to a stated number of candidate sites.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.