It is the question that comes up more than any other, usually from someone who has just been asked for one by a case officer and wants to know what they have let themselves in for. The short answer for most older outbuildings is yes, probably — but the longer answer is more useful.
All bat species in Northern Ireland are legally protected, along with their roosts, under the Wildlife (Northern Ireland) Order 1985 as amended and the Conservation (Natural Habitats, etc.) Regulations (Northern Ireland) 1995 as amended. A roost is protected whether or not bats happen to be in it on the day.
A council determining a planning application has to be satisfied that granting permission will not lead to an offence being committed. If a proposal involves works to a building that could support roosting bats, the council needs evidence one way or the other before it can decide. That evidence is the survey.
Not every building needs surveying. The features that raise the question are reasonably consistent:
A modern shed with a sealed profile-metal roof in the middle of a hard yard is a very different proposition from a stone byre with a slate roof beside a mature hedgerow. Both can be assessed; only one of them is likely to lead anywhere.
Stage one: preliminary roost assessment. A daytime inspection, inside and out, looking for droppings, urine staining, feeding remains, cobweb-free access gaps and anything else that indicates use. The building is then scored for roost potential — negligible, low, moderate or high. This can be done at any time of year, including mid-winter.
Stage two: dusk emergence surveys. Needed wherever stage one finds anything above negligible potential. Surveyors watch the building from dusk, using bat detectors, to record any bats emerging from it. Low suitability normally warrants a single precautionary visit, moderate two and high three, spread across the season.
It is worth being clear that low suitability is not the same as no survey. A building can look unpromising and still hold a small roost in a single gap under a slate, and once the roof is off there is no way back. A precautionary emergence survey on a low-suitability building is a modest cost set against that risk — which is why it is the standard approach here rather than an optional extra.
This is where schemes lose months. Emergence surveys can only be done when bats are active, broadly May to August, with April and September carrying caveats. There is no way to shortcut it — a survey in November tells you little that a council is likely to accept.
So if your barn conversion is going in over the winter and the building has roost potential, the realistic position is that emergence surveys cannot start until May. If the preliminary assessment is done in January rather than in August, at least you know that in January and can plan around it.
The practical advice: get the roost assessment done as early as you can, even if the application is months away.
It is worth saying plainly — finding bats usually does not stop a conversion. It changes how the conversion is done and how it is programmed.
What follows is a mitigation strategy: timing works outside sensitive periods, retaining or replacing roost features in the new build, sometimes a bat loft or access tiles, and a method statement for the contractor. Where a roost will be affected, a wildlife licence from NIEA is needed before works start.
Schemes are regularly built around bats. The ones that go badly are the ones where the bats turn up after the roof came off.
It depends on the building and how many visits are needed. A preliminary roost assessment on a single building is the smallest piece of work; emergence surveys add cost per visit. Quotes are given per site, and the roost assessment is always quoted first so you are not committing to visits you may not need.
No. Councils expect survey work to be carried out by a suitably experienced ecologist, and work that involves disturbing bats requires a licence.
Send over the request and the site address. If it is outside the survey season the sensible route is usually to agree a timetable with the case officer rather than let the application be refused for lack of information.
Written by John Corry of Corry Ecology, CIEEM member. General guidance only — every site is different, so take advice on your own proposal.
Send the site address and a short description and I'll come back with a quote and a likely timescale.
