Preventing bat access in domestic dwelling houses
Bats are quite commonly found in people's houses. In most cases people do not even know that they are there and many people live happily with bats. In rare circumstances, some householders can experience problems with bat roosts in their houses, but most of these can be solved relatively easily.
All bats and their roosts receive legal protection. This means that some activities which might affect bats, such as preventing them accessing your property, would be illegal unless carried out under a licence.
Any person who has bats in their house and needs advice on how to solve any problems they may be causing should telephone the Bats in Houses Helpline: 01463 725165 or email [email protected]. If a query cannot be answered on the phone or email, we will arrange for a bat worker to visit your house to collect information about the bats and provide advice to help resolve the problems that bats are causing. If it is the preference of a householder to not live with the bats, a licence will be required to prevent access for bats in the future.
Frequently Asked Questions
How do I prevent access for bats which roost in my dwelling house?
If a licence is issued, you will need to undertake work to prevent bats from accessing your property in the future. This is called an “exclusion” and normally requires a bat “excluder” to be fitted to all bat access points and blocking any other gaps or holes at the same time.
What is a bat excluder?
A bat excluder is essentially a one-way door or flap which allows bats to safely fly out of the roost, but not get back inside – it is a bit like a cat-flap which only opens one way. As bats can climb on rough surfaces (e.g. harled walls and timber), the excluder must be made out of smooth material.
Bats are faithful to their roosts and will always try to find other ways to get back inside the property. Therefore, for the excluder to work successfully, it must be properly fitted and all other holes or gaps that bats could use to gain entry to the property must be sealed at the same time to prevent bats gaining entry. Bats can use gaps as small as 8mm so all gaps or holes of this size or bigger would need to be sealed.
When can a bat excluder be fitted?
Excluders can only be fitted under a licence from NatureScot and must only be fitted in April or during September to October, when bats are active because this is the optimum time to maximise the chances that it will work. Between May-August bats are either heavily pregnant or have dependent young so an excluder must only be fitted from September when the young are fully weaned and are able to fly to ensure baby bats do not get trapped inside the property. An excluder will not be effective in winter because at this time of year bats are inactive and hibernating3.
3 If an excluder was fitted during winter, it would still need to remain in place until April, and because it would be affected by the weather it would require more monitoring and maintenance to ensure that it had not moved or become dislodged, and that it will still work as intended. This is why they should only be fitted when the bats are active.
How do I know where the bat access points are?
It is important to have a good survey done when the bats are active by a qualified and licensed bat worker who can identify all bat access points and other potential access points. Whilst a NatureScot bat worker will do this during their visit, some buildings can be large and complex and they may not be able to confirm all access points during one visit. To be certain that all access points have been identified you may need to employ the services of a licensed bat consultant to conduct further survey.
Will an exclusion be successful in keeping the bats out?
Exclusions can be difficult and complex and there is no guarantee of success. It is important that the advice in this document is followed to optimise the chances of a successful outcome and to prevent the bats from returning. If an exclusion is not conducted properly (e.g. the excluder is not fitted properly and/or all other gaps are not adequately sealed), bats will find a way back inside the property. Contrary to this, a poorly fitted excluder may result in the bats being trapped inside the property and in finding a way out they may enter the living spaces which is not good for people or bats.
Installing a bat excluder
Excluders can only be fitted under a licence from NatureScot. Bat excluders are not available commercially and need to be constructed ‘fit for purpose’ according to tried and tested designs. Attention to detail is critical. We advise that a licensed bat worker is involved in the fitting of the excluder to check that it will not harm bats and is likely to work.
As bats do not always leave the roost every night to feed (e.g. due to cold temperatures, heavy rain or winds) a licence requires that a bat excluder is left in place for at least 14 days to be confident that all bats have left the roost before access points are sealed. This period should be extended if the weather has been unusually cold and/or wet for much of that time.
There are at least two basic designs for one way bat excluders (see p.89 of the Bat Workers’ Manual 3rd Edition) which have been used successfully.
The Tube Excluder
Thicker material (such as the blue temporary drainage piping shown in the photo below) is less likely to be dislodged by the weather but may need to be held in place with screws rather than by staples or tape.
The tube design is best suited to access points of a large size which are close to the wall-head and this would allow the wooden base plate to be fixed to the wall. It is not suitable in situations where there is a narrow access point between barge boards and the wall, or where there are gaps between slates or tiles etc. It is also not suitable for exposed or windy locations because if the plastic gets damaged in the wind it will not work effectively.
The Bat Flap Excluder
The bat flap consists of a flap, a base-layer sheet which goes beneath the flap and a curtain (optional). The bat flap design is best suited to buildings where the bat access is behind soffit/fascia/bargeboards, or between a wall and window frame, because the bat flap can be fixed to the wood over the access point. It is not suitable for use in situations where bats are emerging from under slates.
A step-by-step guide to putting up a bat flap excluder
1. What you will need
Materials to make an excluder can be bought from any DIY store. As each bat access point is different, you would need to consider which of the designs above would be best suited to your house:
- Sheets of acetate or stiff plastic for flaps, base-layers and curtains e.g. suitable plastic would include fertiliser bags, lawn edging plastic, laminator plastic or acetate sheets (an example of the right thickness to be used is the clear stiff plastic used to support the neck area in packaged ‘formal’ shirts).
- Adhesive such as duct tape or electrical tape would be appropriate. Staples could be used and an 8mm staple gun would be suitable and allow staples to be easily removed after without damaging the wood. A powered nail-gun would be more suited for stone/brick/harled buildings. Silicone is often preferred because it peels off easily after use. Polymastic is an option but will be semi-permanent. The area should be dry before using an adhesive, but if walls/fascia/soffits etc., are damp a waterproof grab adhesive is recommended.
- Filler and/or sealant. There are various substances that can be used to block-up bat access points. Silicone is good providing it is put on a clean surface as any dirt would make it ineffective. Polymastic has been used successfully as both a “glue” to fix excluders to walls/timber etc. and as a filler to fill access gaps. Expanding foam is not recommended as bats can get caught up in it. In addition, expanding foam is not stable in sunlight and may contract, leaving gaps which would allow bats back inside.
2. Make a base-layer
The base-layer needs to be fixed firmly flush to the wall to ensure there are no gaps which bats could crawl under, and also to prevent the wind from dislodging it.
3. Make a flap (one-way door)
4. Protect the excluder from the weather
Finally, a large piece of clear plastic sheet (the curtain) can be draped over the whole thing to stop the wind and rain damaging the excluder.
Modifications to the pipe and bat flap excluders are shown in the photos below:
A tube excluder designed to fit corners
Modified bat flap excluder for wide gaps
Modified bat flat excluder
Modified bat flat excluder with pipe
Monitoring the excluder
To check the excluder is working properly, watch at dawn for bats returning to the roost (ideally start an hour before dawn). When the bats return and cannot get back inside through their usual access point, they will look for another way into the building. If all the gaps have been successfully blocked, they will not be able to get back in and will eventually fly away. However, if you do see bats going in other access gaps, these will also require blocking or a bat excluder to be fitted.
You should also check that no bats are stuck inside the excluder and if any bats are stuck, they should be removed ideally without handling them4, but if this is necessary this should only be done by persons wearing thick gloves (such as leather or rigger-type gloves used for gardening), and allowed to fly away. You should also check the excluder regularly to ensure it has not fallen away or become dislodged, especially following heavy rain or high winds.
4 If it is necessary to remove a bat, you should avoid skin contact with it due to the small risk of a rabies type virus. You should wear protective gloves or use a towel to contain the bat. Place the bat in a box or container with air holes, and add a shallow dish with water (e.g. lid from a jam jar or milk bottle) and a small towel for the bat to hide in. At dusk, place the box outside on a wall or windowsill (out of the reach of cats) and partially open it. If the bat will not fly or is behaving aggressively (for example, it is making unprovoked attempts to bite at objects around it) you should contact the Bat Helpline 0345 1300 228 or NatureScot Bats in Houses Helpline 01463 725165 for further advice. If you have, or think you have, been bitten or scratched by a bat, you should seek medical advice without delay.
Removing the excluder
The gap will need to be blocked immediately after the excluder is removed.
Is there help available?
It can be very difficult to achieve a successful exclusion and it requires the exclusion device to be fit for purpose and correctly installed, and all other possible bat access points into the building being properly sealed. Seeking advice from a specialist bat consultant should maximise the chances of success. Often a licensed bat consultant working in tandem with a roofer or joiner is likely to provide the best possibility of achieving a successful exclusion.
For some houses, an exclusion may be particularly complex especially if the building has many bat access points such as under numerous slates or tiles. In such cases, a bat excluder may not be effective and a licensed bat consultant should be able to advise accordingly on what would be most appropriate. If bat access points are beyond the reach of a ladder, scaffolding may be required to undertake this work. In some cases, re-roofing works may be the only way to successfully prevent access for bats in the future.
A list of licensed bat consultants can be found by doing a general internet search for a licensed bat consultant. You could also search on the Chartered Institute of Ecology and Environmental Management (CIEEM) website (choose bats in both the species and licences held boxes). Not all consultants are registered with CIEEM, so we recommend also doing a general internet search. You should check the consultant if they hold a bat licence for Scotland.
Bats are roost faithful and return to the same roosts each year which is why it is often difficult to achieve a successful exclusion. Due to the complexity and cost involved with trying an exclusion, some people choose to continue to live with the bats but confine them to one area of the roof void, in an internal bat box so that they are more manageable, and the droppings can easily be cleaned out once a year in the winter after the bats have left. If you wish to explore this option help and advice may be available and you can contact the Bat Conservation Trust.
Do I still need to fit an excluder if the bats have already gone?
Yes. It is difficult to know when all the bats have left after the summer season as some bats may remain longer in the roost whilst others leave. Some people mistakenly believe that once the bats have left of their own accord after the summer, they will not return so there is no need to fit a one-way excluder. Bats will often return to the same summer roosts each year, therefore, you should complete the exclusion as permitted by your licence if you do not want the bats to return the following year.
Is there any funding available to help with an exclusion?
With the prospect of continuing pressure on public expenditure, we need to be increasingly selective in prioritising projects for support, favouring those that make a particularly strong, strategic contribution to the outcomes identified in our Corporate Plan and unfortunately, NatureScot cannot provide funding to persons wishing to exclude bats from their house.
Can I exclude bats from a building which is not a domestic dwelling house?
NatureScot bat workers only conduct roost visits to domestic dwelling houses where a person lives full time and they are experiencing health and safety problems or concerns with bats. If your query is about any of the following, you would need to seek advice from a licensed bat consultant (see details above) and a licence would be required:
- a second home or holiday home; or
- a non-domestic property (including property owned and run by local authorities, public bodies, charities or commercial organisations, and includes schools, churches, and hospitals); or
- queries related to a development (including domestic dwelling houses) which requires planning permission.