I haven't seen any bats — do I still need a survey?

Yes — bat presence not visible from normal occupation. PRA looks for evidence of past/present roosting. Absence of visible activity doesn't prove absence of roost. LPA increasingly insists on PRA as planning condition for loft conversions in suitable habitat boroughs.

What if I've already started works + find bats?

STOP work immediately. Cover the area to prevent disturbance. Call ecologist + Natural England bat helpline (0345 1300 228). Continuing work after discovering bats is criminal offence — strict liability. Builderr policy: PRA before any roof void access on every project, no exceptions.

Can I survey outside May–September?

PRA: yes — daytime inspection year-round. Emergence/re-entry survey: NO — bats inactive Oct–April, survey ineffective. If project starts winter, PRA can proceed; emergence surveys booked next May–Sept; works programmed around survey window. Plan 6–9 months ahead for projects needing full bat survey package.

Bat Survey London Renovation 2026 | Builderr

When Is a Bat Survey Required for a London Renovation?

Bat survey is required for any London renovation affecting roof voids, lofts, soffits, fascias, chimneys, or mature trees where bats may roost. All UK bat species protected under Conservation of Habitats + Species Regs 2017 + Wildlife + Countryside Act 1981 — criminal offence to disturb roost. Preliminary Roost Assessment (PRA) £450–£950; if bats suspected, emergence/re-entry survey £1,800–£4,500 over 2–3 dusk visits May–September. EPS Mitigation Licence + bat-friendly design if roost confirmed.

Legal protection + offences

All 17 UK bat species (8 common in London — Common pipistrelle, Soprano pipistrelle, Nathusius pipistrelle, Brown long-eared, Noctule, Serotine, Daubenton's, Natterer's) European Protected Species (EPS) under Conservation of Habitats + Species Regs 2017. Offences: kill/injure/capture; damage/destroy roost (even when bats absent — roost protected when not in use); disturb. Criminal penalties: up to £5,000 fine + 6 months prison per offence per bat. Roof void, loft, soffit, fascia, ridge, gable end, chimney, hollow tree, basement, cellar — all potential roost sites. London hotspots: Richmond, Bromley, Sutton, Barnet — leafy boroughs with mature housing + green space; central London less common but still recorded. Planning condition or pre-commencement survey routinely required by LPA where habitat suitable.

Survey types + timing

Preliminary Roost Assessment (PRA): daytime inspection by licensed ecologist — external + internal inspection looking for droppings, urine staining, scratching, dead bats, suitable access (>15mm gaps), prey remains. Cost £450–£950. PRA categorises building: Negligible / Low / Moderate / High suitability. Negligible: no further survey. Low: 1 emergence survey. Moderate: 2 surveys. High: 3 surveys (one emergence + one re-entry minimum). Emergence/re-entry surveys: dusk + dawn observation with bat detectors May–September only (bats roost in summer; winter inactive). 2 surveyors stationed around building, recording emergence patterns + species. Cost £1,800–£4,500 for 2–3 visits. Tree surveys: similar approach for mature/veteran trees in BS5837 scope.

Mitigation + EPS licence

If active roost confirmed: works require EPS Mitigation Licence from Natural England (cost £0 application + £2,800–£8,500 ecologist preparation). Licence application includes: roost description, species, importance assessment, methodology to avoid harm, mitigation measures, monitoring plan. Typical mitigation: time works outside hibernation/maternity periods, install bat-friendly access in new roof, provide alternative roost (bat box), retain key roost features, supervise sensitive works by ecologist. Cost adds £4,500–£18,500 to typical loft conversion budget. Licence determination 30 working days standard, longer for complex sites. Builderr ecologist contact: PRA results within 5 working days; surveys booked May–Sept queue early.