What waiting for the bat survey season costs a scheme
The real cost of bat surveys is the season you lose by asking too late. How to price the holding cost, when a condition will not do, and the licensing routes that shorten the wait.
The bat survey season delay cost is rarely the price of the survey. It is the cost of holding a scheme still for up to nine months because the emergence surveys could not be done in October. A preliminary roost assessment can happen any time of year. Emergence and re-entry surveys cannot, and if you miss the window you wait for the next one, paying interest, fees and inflation the whole time.
That is the calculation to make at feasibility, not after the architect has produced drawings.
The survey windows that create the delay
Bat activity surveys depend on bats being active and detectable. The Bat Conservation Trust good practice guidelines set the survey season for emergence and re-entry work from May to September, with May to August the optimal period, and the number of visits scaling with the roost suitability the preliminary assessment identified: broadly one visit for low suitability, two for moderate and three for high, spaced across the season rather than in one week.
Other species stack on top of the same summer. Great crested newt environmental DNA sampling runs from 15 April to 30 June. Reptile surveys need April to October with spring and early autumn best. Breeding bird surveys run March to August. Botanical survey needs the growing season. A site with a derelict outbuilding, a pond within 250 m and rough grassland can therefore need three separate seasonal programmes, and the last one to finish sets the submission date.
The consequence is a hard calendar. A scheme that reaches the ecology question in early September may get one bat visit in and then stop until the following May.
Where a preliminary assessment can be done at any time of year
The Preliminary Ecological Appraisal and the preliminary roost assessment are the parts you can always do. A suitably qualified ecologist inspects the buildings and trees for roosting features, droppings, staining and feeding remains, walks the habitats, checks the records held by the local environmental records centre and the statutory designations, and then tells you two things: whether further survey is likely, and which windows you need.
Commission that in the first fortnight. It is the least expensive report in the whole evidence base and it is the one that tells you whether your programme has a nine-month hole in it.
Sometimes the answer is reassuring. A 1990s brick and concrete-tile bungalow with sealed eaves, no roof void access and no trees to be felled may return a negligible suitability finding, and the ecologist can write a short justification for no further survey. Councils accept that when it is properly evidenced and the author is competent.
What holding a scheme for a season actually costs
Holding costs are arithmetic, and the method is public even though the inputs are yours. Four items usually move.
Finance on the land or the bridging facility accrues monthly whether or not anything happens. Professional fees already committed sit as work in progress, and teams demobilised for six months cost money to remobilise. Build cost inflation runs against the appraisal. And any option, promotion agreement or conditional contract has a longstop date that a nine-month delay can put at risk.
An illustrative example. Assume a plot held at £320,000 on a facility charging 9 per cent a year, a nine-month wait, and a build contract that would have been let at the start of that period. Finance alone is roughly £21,600 over the nine months. Add remobilisation of the design team, a further season of site security and any uplift in the tender price and the delay comfortably exceeds the cost of the surveys several times over. Every figure here is illustrative and you should run it with your own facility rate, land value and programme.
That is the number to put in front of a client who wants to skip the ecologist to save a four-figure fee. The same logic applies to every seasonal or lead-time item in the evidence base, which is why utility connection costs and lead times and contaminated land investigation programmes belong on the same programme sheet as the ecology.
Whether the council will accept a condition instead
Usually not, where the likelihood of bats is real. National planning practice guidance on the natural environment is clear that the presence of a protected species is a material consideration and that survey work should be done before the application is determined where there is a reasonable likelihood of the species being present. Deferring that work to a condition is not acceptable in those circumstances.
There is a legal reason behind it. Bats are European protected species under the Conservation of Habitats and Species Regulations 2017, and where a proposal is likely to offend the protection the authority has to consider the three derogation tests before granting permission. It cannot do that without knowing what is there. A Protected Species Survey has to be carried out by a suitably licensed ecologist, and a PlanScope draft is a starting point for that professional rather than a substitute for the survey.
Where suitability is demonstrably low, a precautionary working method secured by condition is sometimes agreed: a toolbox talk, a soft-strip under ecological watching brief, and a stop-work protocol if a bat is found. Ask for that only when the ecologist supports it in writing.
Licensing routes that shorten the wait
Two routes cut time out of the programme, and both are underused.
Natural England operates class licences for low-impact bat works, which registered consultants can use for schemes affecting small numbers of common species in low-conservation-significance roosts. That removes the individual licence application and its determination period from the critical path, though the survey evidence is still needed.
For great crested newts, district level licensing lets a developer pay into a strategic habitat scheme instead of carrying out pond-by-pond survey and on-site mitigation, where the local authority takes part. Where it is available it can remove the eDNA window from the programme entirely. Check participation with the authority early, because coverage varies and the charge depends on the impact zone.
Programming the ecology work from feasibility
Treat the ecology calendar as a fixed constraint and work backwards from the submission date.
- Week one: commission the preliminary ecological appraisal and the preliminary roost assessment.
- On receipt, mark the required windows on the programme and identify the last survey visit.
- Book the ecologist for those visits immediately, because good practices fill their summer diaries by March.
- Run the survey season in parallel with design development, pre-application advice and the drainage and access work.
- Complete the biodiversity metric baseline in the same growing season as the habitat survey.
- Allow time after the final visit for reporting, the impact assessment and any licence application.
Point five matters more than it looks. Mandatory biodiversity net gain needs a habitat condition assessment done when vegetation can be identified, so a winter baseline is contestable. Getting the metric baseline from the same summer visit avoids a second season.
Building the ecology line into the appraisal
Put three lines in the feasibility appraisal rather than one. The survey fee, the programme allowance in months with the window named, and the holding cost of that allowance at your finance rate. A scheme that shows all three is a scheme where nobody is surprised in September.
One honest uncertainty. Survey effort is a matter of professional judgement, and two competent ecologists can reach different conclusions on how many visits a moderate-suitability building needs. Where the difference is one visit against three, ask the authority's ecologist what they will accept before you book.
See PlanScope pricing for the report side of the work: one free report, £50 per report, or Professional for unlimited reports.
This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it. For specialist technical reports, qualified professional input may be required.
PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.
Frequently asked questions
When can bat surveys be carried out?
A preliminary roost assessment can be done at any time of year. Emergence and re-entry surveys need the active season, which the Bat Conservation Trust good practice guidelines put at May to September with May to August optimal. The number of visits scales with roost suitability and they must be spread across the season rather than clustered.
Can the council condition the bat survey instead of requiring it upfront?
Not where there is a reasonable likelihood of bats being present. National planning practice guidance expects survey work to be complete before determination in those circumstances, because the authority must consider the derogation tests under the Conservation of Habitats and Species Regulations 2017. A precautionary method statement is sometimes accepted where suitability is clearly low.
How do I work out what a season's delay costs?
Take the finance cost on the land or facility for the delay period, add remobilisation of the design team, continuing site holding costs and any build cost inflation between the original and revised tender dates. Then check whether an option or conditional contract longstop date is at risk. Use your own facility rate rather than a generic figure.
Does district level licensing avoid great crested newt surveys?
Where the local authority takes part, district level licensing lets a developer pay into a strategic habitat scheme instead of carrying out pond survey and on-site mitigation, which can remove the 15 April to 30 June sampling window from the programme. Coverage varies by area and the charge depends on the impact zone, so confirm participation early.
Should the biodiversity metric baseline be done at the same time?
Yes wherever possible. Habitat condition assessment for the statutory metric needs vegetation that can be identified, so a winter baseline is open to challenge. Capturing the metric baseline during the same growing season as the ecological survey avoids losing a second season to a repeat visit.
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.