Why Bats Matter in Planning
All bat species in the UK are protected under the Wildlife and Countryside Act 1981 (as amended) and the Conservation of Habitats and Species Regulations 2017. It is a criminal offence to:
- Intentionally kill, injure, or take a bat
- Intentionally or recklessly disturb a bat in a roost
- Damage, destroy, or obstruct access to a bat roost — even when bats are not present
This last point is critical: roost protection applies to the structure used by bats, not only to the bats themselves. Damaging the loft structure during a conversion — even outside bat season — can constitute an offence if bats have used that space.
When Is a Bat Survey Required?
A bat survey is required when:
- A planning application is submitted for work that could affect a potential roost — particularly loft conversions, roof replacements, and alterations to roof voids
- The local planning authority's ecologist has requested one as a condition of planning
- A building survey or visual inspection has identified features that bats might use (gaps in tiles, soffits, fascias)
Many London planning authorities now routinely require a preliminary roost assessment (PRA) for planning applications involving loft works.
Types of Bat Survey
Preliminary Roost Assessment (PRA)
A desk study and external and internal visual inspection by a licensed ecologist. The ecologist assesses whether the building has features that could support bats. Takes approximately 1–2 hours on site.
Outcome: low, medium, or high potential for roosts. If potential is assessed as negligible, no further surveys may be needed. If potential is assessed as medium or high, further surveys are required.
Emergence and Re-Entry Surveys
The definitive survey involves watching the building at dusk (emergence) and dawn (re-entry) to observe bats leaving or entering the roost. These must be carried out:
- During the active bat season (April–October; peak season May–August)
- A minimum number of visits is required depending on roost potential
If a roost is confirmed, a mitigation plan is required.
What Happens If Bats Are Found?
If a bat roost is confirmed, the loft conversion can still proceed — but additional steps are required:
- Mitigation plan: Prepared by the ecologist — typically includes timing the works to avoid disturbing bats, providing replacement roost features (bat boxes or built-in roost spaces), and a watching brief during the works
- European Protected Species (EPS) licence: If works cannot be timed to avoid disturbance, a licence from Natural England is required. This takes 30 days to process and must be approved before works start.
- Planning condition: The planning authority will typically condition that works follow the mitigation plan and that a monitoring report is submitted after completion
Timescales
Bat surveys are highly seasonal. If surveys are needed and it is outside the active season, you may need to wait until the following spring to carry them out — potentially delaying the project by months.
Build this into your programme early. If there is any possibility of bat surveys being needed, commission the PRA as soon as the project is confirmed, ideally before the planning application.
Cost
| Survey Type | Approximate Cost |
|---|---|
| Preliminary Roost Assessment | £300–£600 |
| Emergence/re-entry survey (per visit) | £150–£300 |
| Full bat report with mitigation plan | £800–£2,000 |
| EPS licence application | £300–£600 |
RCB Design & Build
RCB flags the need for bat surveys at the pre-planning stage for loft conversion projects in London and coordinates licensed ecologists where required. We incorporate bat survey timescales into the project programme to avoid delays.