Why Your Barn Conversion Needs a Specialist Ecology Survey

Barn conversions are one of the most popular routes to a countryside home, and one of the most likely projects to be delayed by wildlife legislation. Old agricultural buildings are exactly the kind of structure that bats and barn owls depend on, and both are protected by law. Understanding what a survey involves and when to commission one can be the difference between a smooth planning process and a project held up for months. 

Why barns are a magnet for protected species 

Traditional barns offer everything a roosting bat or nesting barn owl needs: undisturbed roof voids, gaps in weatherboarding and fascias, stable temperatures and easy access. The less a barn has been altered, the more attractive it tends to be. Even buildings that look derelict or show no obvious signs of use on a casual walk-round, can support roosts that are only detectable through a proper inspection. 

This is why ecology surveys are so often required for barn conversions specifically, more so than for many other types of development. 

What the law requires 

All bat species are protected under the Conservation of Habitats and Species Regulations 2017, and it is an offence to disturb, damage or obstruct access to a roost, whether or not the disturbance was intentional. Barn owls carry their own protection under Schedule 1 of the Wildlife and Countryside Act 1981, which safeguards them against disturbance while nesting, on top of the standard protection given to all wild birds. 

Local planning authorities treat this as a material consideration. Natural England's standing advice sets out that a survey should be requested wherever a building could support roosting, commuting or foraging bats, and barn conversions are named explicitly as a typical trigger. 

Permitted development does not remove the legal risk 

Many barn conversions in England now proceed under Class Q permitted development rights, sometimes without a full planning application or an ecology condition attached - it is a common misconception that this route sidesteps the need for a survey. 

Permitted development changes the planning process, not the wildlife law - if bats or nesting barn owls are present and a project proceeds without them being identified and safeguarded, the person carrying out the works is liable for an offence, regardless of what planning route was used to get there. A specialist survey is what protects you from that risk, not the planning permission itself. 

What a survey involves 

Most projects start with a Preliminary Roost Assessment (PRA), a daytime inspection by a licensed ecologist looking for droppings, staining, feeding remains and potential access points. A PRA can be carried out at any time of year and is usually valid for up to two years. 

If the PRA finds evidence of bats, or judges the building to have potential to support them, a further emergence or re-entry survey is required. These are seasonally restricted; they can only be carried out during the active bat season, broadly May to September, with at least one survey falling within the optimal window of mid-May to August. 

Barn owl surveys follow a similar logic, though nest checks are most reliable between March and June, and any works affecting an active nest must generally avoid the March to August breeding period altogether. 

Survey timing 

The most common reason barn conversion projects stall is not that bats or owls are found, but that the seasonal survey window was missed. A PRA commissioned in November can still need a follow-up emergence survey that cannot happen until the following May, pushing a project back by six months or more. 

Commissioning your ecology survey at the earliest possible design stage, well before you plan to submit for planning or start works is the single most effective way to avoid this. A PRA in winter still leaves time to schedule any further surveys for the following season, rather than losing it entirely. 

What happens if works begin before a survey 

Beyond the legal exposure, a missing or inadequate survey is one of the most common reasons planning applications are delayed or refused for barn conversions. If evidence of bats or barn owls turns up once work has started, the consequences are more serious: works can be stopped on site, and prosecution is possible. A proportionate, correctly timed survey resolves the issue early and, in most cases, does not stop a conversion from going ahead. 

If you are planning a barn conversion, the right time to speak to an ecologist is before your design is finalised, not once the application is already in. Get in touch with The Ecology Co-op to find out what your project needs and when.