A craftsman’s guide to working alongside nature on historic facades
You’re up on the scaffold. The work is going well. You open up a joint, start removing a section of failed render, or lift a loose tile from a cornice — and something moves.
A bat. A swift. A kestrel looking back at you from a cavity you didn’t know was there.
It happens more often than people talk about. Historic buildings — with their thick walls, their cavities, their untouched roof spaces and their sheltered cornices — are some of the last refuges for species that have lost most of their natural habitat to modern construction. As a craftsperson working on these buildings, you will encounter them. The question is: what do you do when you do?
The legal reality — this is not optional
Let’s start with the law, because it matters more than most people on a restoration site realise.
In most European countries, a significant number of species that inhabit historic buildings are strictly protected by law. This means not just that you cannot harm them — it means you cannot disturb them, damage their nesting or roosting sites, or in some cases even approach them during certain periods of the year, without specific authorisation.
Bats are the most comprehensively protected. Across the European Union, all bat species are protected under the Habitats Directive — which means that in every EU member state, it is illegal to deliberately capture, injure or kill a bat, to damage or destroy a breeding site or resting place, or to deliberately disturb bats, particularly during breeding, rearing, hibernation or migration. This protection applies whether the bats are present or not — a roost that is currently empty is still a protected roost.
Swallows and house martins — the barn swallow (Hirundo rustica) and the house martin (Delichon urbicum) — are protected across most of Europe. Their nests, oncebuilt and occupied, are protected during the breeding season. In many countries, it is also illegal to remove an occupied nest or to destroy a nest that has been used in the current season, even after the birds have left.
Common swifts (Apus apus) deserve particular attention for anyone working on historic buildings. Swifts nest in very specific locations — narrow crevices under roof tiles, gaps in masonry, cavities behind fascia boards — and they return to exactly the same nest site year after year. A swift that finds its entry point blocked on return from its African migration has nowhere else to go. In the UK, swifts are a species of conservation concern. In Belgium and the Netherlands, they are also protected. Blocking a swift entry point — even accidentally, as part of otherwise well-intentioned restoration work — can be a criminal offence.
Barn owls, tawny owls and little owls nest in roof spaces, church towers, and the cavities of large historic buildings. Their nests are protected during the breeding season.
Kestrels (Falco tinnunculus) — the small falcon that hunts by hovering — frequently nest in the cornices, parapets and towers of large historic buildings. Their nests and eggs are protected.
When do you stop work?
This is the practical question that every craftsperson needs to be able to answer.
The general principle across most European legislation is that active nests — nests containing eggs or young — must not be disturbed. This means that if you discover an active nest in the course of restoration work, work in that area must stop until the nest is no longer active.
For bats, the situation is more complex. Bat roosts are protected year-round, not just during the breeding season. If bats are discovered roosting in a building that is about to undergo restoration, specialist advice must be sought before work proceeds. In most countries, this means contacting the national or regional nature conservation authority and, in many cases, commissioning a bat survey by a licensed ecologist.
This sounds bureaucratic. It is, in practice, also the right thing to do — both legally and ethically.
The timing question — plan around the calendar
The single most effective thing a craftsperson or property owner can do is to plan restoration work around the natural calendar.
For most of northern and western Europe, the key periods to avoid — or to plan carefully around — are:
March to August — the main breeding season for most birds. Swallows, house martins, swifts, owls and kestrels are all potentially nesting during this period. Work on roofs, cornices, and areas with known or suspected nest sites should ideally be completed before March or deferred until September.
May to August — the maternity roost season for bats, when females gather to give birth and raise their young. This is the period when bat roosts are most sensitive to disturbance. Major work affecting roof spaces, wall cavities, and other known bat roost areas should be planned outside this window where possible.
If a project cannot avoid these periods — and on large restoration projects, it often cannot — the answer is not to proceed regardless. It is to seek specialist advice, obtain any necessary authorisation, and plan the work sequence to minimise disturbance to the protected species present.
What to do when you find them
If you find bats: Stop work in the immediate area. Do not handle the bats. Contact the relevant nature conservation authority or a licensed bat surveyor. In most countries, there are bat helplines specifically for situations like this.
If you find an active bird’s nest: Stop work in the immediate area. Leave the nest undisturbed. Mark the location so that work can resume once the nest is no longer active — typically once the young have fledged and left.
If you find swift entry points: Note their location before work begins. If the entry points must be sealed as part of the restoration, plan to install purpose-made swift bricks or nest boxes in the same area to compensate for the lost access. In some countries, this mitigation is a legal requirement.
Mitigation — giving something back
Beyond the legal minimum, there is a broader opportunity here that craftspeople and property owners would do well to consider.
Historic buildings that have housed bats, swifts, swallows or owls for generations are providing something genuinely valuable — shelter for species under significant pressure from habitat loss. A restoration project that takes this seriously — that plans around the breeding calendar, installs replacement nest sites where existing ones are lost, and leaves access points where they can safely be retained — is doing something that goes beyond the technical restoration of the building.
I have put up swift nest boxes on the rear facade of my own house, oriented carefully to give the best chance of occupation. I have installed bat boxes in sheltered locations. A butterfly house with the narrow slots that exclude birds. None of these have been occupied yet — these things take time, and the orientation and location have to be right. But the gesture matters, and the knowledge that the building is ready to welcome these animals back when they choose to come matters too.
For swifts specifically: the orientation of the entry point matters enormously. Swifts prefer north to east facing entries, away from direct afternoon sun. They need a clear flight path — they cannot take off from the ground, so the entry must be high enough to allow them to drop into flight on exit. Getting these details right is the difference between a nest box that is used and one that is ignored.
A practical note for property owners
If you own a historic building and are planning restoration work, the most important step you can take is to have the building surveyed for protected species before work begins — not after the scaffold is up and the first section of cornice has come off.
A pre-works survey by a licensed ecologist is not an obstacle to restoration. It is information that allows the restoration to be planned intelligently, with the right work sequences, the right timing, and the right mitigation measures built in from the start.
It is also, in most countries, a legal requirement for work on buildings where protected species are known or likely to be present.
A question to the Guild
Have you encountered protected species on a restoration project? How did you handle it — and did the presence of bats, swifts, or nesting birds affect the project timeline or scope?
And has anyone successfully installed swift bricks or bat boxes as part of a facaderestoration — and seen them occupied? The Guild would love to hear what worked.
Because a building that has housed these animals for a century deserves to keep doing so — even after the scaffold comes down.
RestoreFacade Guild — for the craftspeople who understand that restoration means respecting everything that lives in a building, not just the masonry.