Walkthrough: a bat roost found before a demolition
Droppings on a beam in February meant a demolition in October. Where the seven months went, and what could have been done differently.
A preliminary roost assessment on a single-storey outbuilding found bat droppings on a beam, and the demolition that was due to start in March happened in October. This walkthrough follows that illustrative scheme through the survey season, the mitigation design and the licence, and sets out where the seven months went.
The scheme is invented to show the sequence. The legal tests, survey seasons and licensing steps are the real ones.
The preliminary roost assessment result
The site was a bungalow plot with a detached brick and slate outbuilding, to be demolished and replaced with a single new dwelling. The self-builder commissioned an ecologist in early February, on the architect's advice, after the council's validation list flagged that a preliminary ecological appraisal would be required where buildings were to be demolished.
The assessment took half a day. The ecologist found droppings on a tie beam below a gap where the slates met the gable, staining around that gap, and a roof void with no lining. No bats were seen, which is normal in February, and the building was assessed as having moderate potential to support roosting bats.
Moderate suitability triggers further survey. The report recommended dusk emergence and dawn re-entry surveys in the active season, following the number of visits set out in the published good practice guidance for a building of that suitability.
Two things the self-builder had not expected. The droppings alone established that a roost was present at some point, and a roost is protected whether or not bats are in it. And the survey season had not started.
Emergence surveys and the season
Emergence and re-entry surveys are carried out in the bat active season, broadly May to September with the most reliable results between May and August. The February assessment therefore produced a three month wait before anything further could happen.
The first survey took place in late May, with two surveyors positioned to cover the gable and the rear elevation from before sunset. One common pipistrelle emerged from the gap at the gable about twenty minutes after sunset. The second survey, a dawn re-entry in June, recorded two individuals returning to the same feature.
That result characterised the roost: a small day roost used by a low number of common pipistrelles, with no evidence of a maternity colony. The distinction matters enormously to what follows. A maternity roost of a rarer species would have taken the scheme into a different category of mitigation, a longer licence process and a materially different cost.
The ecologist's report went to the council in July, with the planning application.
Mitigation design and the bat loft
Mitigation had to replace what was lost, in the same place, before it was destroyed.
The design provided a purpose-built bat access into the roof void of the new dwelling: a gap at the gable apex matching the original feature, leading into a void with rough-sawn timber for roosting surfaces, no breathable membrane of the type that traps bats, and no lighting. The new void is accessible for monitoring from a hatch.
Two bat boxes went on retained mature trees at the boundary as temporary provision during the works. The demolition method changed: the roof would be stripped by hand under the supervision of the licensed ecologist rather than pulled down by machine, with the timing set outside the hibernation period and outside the maternity season.
The external lighting scheme was redrawn. The original design had a floodlight on the gable that would have illuminated the new access point, which would have made the mitigation worthless. The replacement scheme used low-level bollards on the drive and a cowled light at the door, with nothing directed at the gable or the tree line.
The council's ecologist reviewed all of this before the application was determined, which is the correct sequence. Presence and absence had been established, so the authority could apply the derogation tests properly rather than deferring the question to a condition.
The licence application to the regulator
Planning permission was granted in September. The licence application followed, and this order is not optional: a European protected species mitigation licence is applied for once planning permission is in place, because the regulator needs to know what has been permitted.
The licence application is made by the licensed ecologist on behalf of the applicant and has to satisfy three tests derived from the Conservation of Habitats and Species Regulations 2017. That the work is for a purpose within the permitted categories, which for development is usually imperative reasons of overriding public interest. That there is no satisfactory alternative. And that the action will not be detrimental to the maintenance of the population of the species concerned at a favourable conservation status.
The application includes the survey data, a method statement, a reasoned statement addressing the three tests, and drawings showing the mitigation. Determination takes weeks rather than days, and the regulator can and does ask questions.
This is work only a suitably licensed ecologist can do. The licence names the ecologist, the site and the methods, and carrying out the work outside those terms is an offence under the 2017 Regulations and the Wildlife and Countryside Act 1981.
How the programme changed
Set out against the original plan, the sequence looked like this:
- February: preliminary roost assessment, moderate suitability, survey recommended
- March: original demolition date, not achievable
- May and June: emergence and re-entry surveys
- July: ecology report finalised, planning application submitted
- September: planning permission granted
- October: licence issued, hand strip of the roof under supervision, demolition completed
Seven months from assessment to demolition, of which three were spent waiting for a season that could not be brought forward.
The self-builder's mistake was not commissioning the ecologist late. February was reasonably early. The mistake was assuming that an ecology report was a document to be produced rather than a process with a calendar attached. Had the assessment been done the previous September, the surveys could have run the following May with the application submitted in June, saving nothing on the season but removing the wasted March start date and the standing costs that went with it.
Conditions and post-construction monitoring
The permission carried conditions requiring the approved mitigation to be implemented in full, the lighting scheme to be built as approved with no additional external lighting without consent, and a post-construction report confirming the bat access had been built as designed.
The licence itself carried further requirements, including supervision at specified stages, a record of any bats found and a report to the regulator after completion. Some licences require monitoring in subsequent seasons to confirm the mitigation is being used.
None of this ends at practical completion. The lighting condition in particular runs with the property, and a later owner who fits a security light on the gable would be in breach of it.
Cost and time consequences
The direct costs were the ecologist's fees for the assessment, two survey visits with two surveyors each, the licence application and the supervision. The indirect costs were larger: seven months of holding costs on the site, a rescheduled contractor and a build that ran through a winter rather than a summer.
The lesson generalises beyond bats. Ecology, flood risk and heritage all have their own sequencing, and each can be the item that sets the programme. A scheme delayed by flood risk evidence follows a similar pattern to the one described in a new dwelling in Flood Zone 2, and the sequencing question on a barn is set out in a barn converted under Class Q prior approval. Where a scheme is phased, the same discipline applies at each stage, as in an outline application and reserved matters.
Commission the preliminary ecological work at the point you start thinking about the site, not at the point you start thinking about the application.
This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. Protected species survey work and any mitigation licence require a licensed ecologist. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.
Enter your postcode on PlanScope to see which reports a demolition and rebuild is likely to need.
Frequently asked questions
Is a roost protected if no bats are present?
Yes. A roost is protected under the Conservation of Habitats and Species Regulations 2017 and the Wildlife and Countryside Act 1981 whether or not bats are using it at the time. Droppings or staining at an access point are enough to establish that the building has been used, which triggers further survey.
When can emergence surveys be carried out?
In the bat active season, broadly May to September, with the most reliable results between May and August. A preliminary assessment carried out in winter cannot be resolved until the following spring, which is why an autumn or winter assessment commonly costs a scheme a full season.
Do I apply for the bat licence before or after planning permission?
After. A European protected species mitigation licence is applied for once planning permission is in place, because the regulator needs to know what has been permitted before assessing the three derogation tests. The licence application is made by the licensed ecologist and takes weeks rather than days.
What do the three derogation tests require?
That the work falls within a permitted purpose, which for development is usually imperative reasons of overriding public interest; that there is no satisfactory alternative; and that the action will not be detrimental to maintaining the population of the species at a favourable conservation status. All three must be satisfied.
Why does the lighting scheme have to change?
Because lighting a bat access point makes the mitigation useless. A floodlight on a gable containing a new roost access will deter bats from using it, so lighting schemes are redrawn to keep light off access points, roof lines and tree boundaries, and the resulting scheme is usually secured by condition.
Can demolition be carried out by machine once a licence is granted?
Not usually where a roost is present. Licences commonly require the roof to be stripped by hand under the supervision of the licensed ecologist, at times outside the hibernation and maternity periods, with any bats found recorded and reported to the regulator after the works are complete.
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.