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B A T S

A guide for builders and surveyors

Introduction

Bats can be found in all kinds of buildings, usually in the roof but also in other areas. All professional builders and surveyors should be aware that any roof or building is a potential bat roost and should therefore, as a matter of course, check for the presence of bats or bat droppings prior to carrying out any work.

In a small roof, five minutes spent specifically on this would find any established roosts. In larger roofs, about the same time should be spent on each roof section. This leaflet is designed as a guide on how to detect if bats are present and what to do in the event of finding a bat roost.

The law

The Wildlife and Countryside Act 1981 (amended by the Environmental Protection Act 1990) gives full protection for bats. It is illegal not only to kill, injure or handle any bat but also to damage, destroy or obstruct access to any place that a bat uses for shelter or protection, even if bats are not present at the time. It is also illegal to disturb a bat while it is occupying such a place.

In this context 'damage' means 'to make worse for a bat' and so can include such operations as timber treatment with the toxic chemicals found in wood preserves.

The Act provides defences so that building, maintenance or remedial operations can be carried out in places used by bats. However, these defences cannot be relied upon unless the Countryside Council for Wales has been notified and been given time to give advice.

This explanation should only be regarded as a guide to the law. For more details reference should be made to the Wildlife and Countryside Act 1981.

Bats in buildings

Many species of bat are dependent on buildings for roosting, with each species having its own preferred type of roost. Most species roost in crevices such as under ridge tiles, behind roofing felt or in cavity walls and are therefore not often seen in the roof space.

The species most often found in houses is the pipistrelle, which uses roofs for breeding during the summer and generally disperses in the autumn. Particularly favoured roosting sites are at gable ends, beneath roof tiles, behind soffitts, at the top of cavity walls near chimneys and behind bargeboards. Usually, roosting pipistrelles will not be visible. The most likely places to find droppings in the roof void are at the gable end walls, and along the eaves; droppings may also be seen around the outside of the house.

The brown long-eared bat is probably the second most common species in Britain and is the one most likely to be encountered in the roof void. Droppings are usually found scattered over the floor or concentrated in piles, typically beneath the ridge beam.

In Wales, we are fortunate to have two very rare species of horseshoe bat. While other bats spend much of their time tucked in cervices, horse shoe bats always roost hanging free by their feet with their wings wrapped round their bodies and can often look like pairs of plums hanging from the roof. Horseshoe bats are found in the lofts, stables, outbuildings and boiler rooms of large country houses which provide ideal warm conditions for nursery roosts. Droppings are typically in piles below the ridge-beam.

A number of other bat species also use buildings. The roost position is variable and droppings can be found in similar places.

Identification of roosts

Bat roosts are protected even when bats are temporarily absent because, being creatures of habit, they usually return to the same roost site every year. Therefore, it is very important that builders and surveyors are able to recognise roosts even if they see no bats.

The key identification feature is the presence of droppings. These are dark brown or black and vary between 4 and 8mm long, the same size as, or a little larger than a mouse dropping. Because they consist largely of fragments of insects, they crumble easily to a fine powder when pressed between the fingers. In contrast, mouse or rat droppings are pasty when fresh and become increasingly hard as they dry. Bird droppings usually have some white uric acid crystals associated with them and are generally less well formed, although swallow or house martin droppings can sometimes look like old bat droppings.

The accumulation of droppings into piles beneath ridge beams, hips or around chimney or gable ends is typical of bats. It is also important to note that the quantity of droppings readily visible in a roof does not always provide a guide to the numbers of bats using a roost. Often bats will spend a greater part of their time concealed in crevices, only occasionally entering the easily accessible areas of the roof, so that only a small scattering of droppings may be obvious.

Search technique

A suggested search technique for houses:

1. Ask the occupiers whether they are aware that they have bats or if bats have ever been found in the house.

2. Examine the loft for droppings, concentrating on the area beneath the ridge, down hips and over bays, around chimneys and gables and all around the eaves. Much of this can be done during the course of a normal survey.

3. In the summer months, check for presence of droppings on the outside of the house, most commonly on window ledges, stuck to walls or on the ground, beneath the gable apex.

4. Check for the presence of bats by listening for their 'chittering' noises in warm weather and by shining a light along the ridge beams and over the brickwork. However, it must be stressed that bats are rarely seen during the day.

Churches and other large non-domestic buildings may require a different technique but the principles still apply. Ask staff about bats and check for droppings on walls, floors, pews etc.

What to do if a bat roost is found

If evidence of bats is found and any action is proposed which would affect the bats or their roosts, the Countryside Council should be informed and allowed time to advise on any special precautions which may be necessary. Such actions would include for example: