Build a bat box
Building a bat box gives them somewhere safe to roost, raise their pups and sleep during the day. Bats are having a tough time finding food to eat, and many of their natural roosting places are being damaged and destroyed. You'll want to keep an eye out for tiny common pipistrelles - they are one of our smallest bats, weighing the same as 10 paperclips and are small enough to fit in a matchbox! You can build and put up a bat box whenever you like. Once you have put it up don’t disturb it, as bats are protected by law. If you don't have the time or tools to make a bat box, why not buy one or two. Research has shown that bats are more likely to roost if you have several boxes up near each other.
The basic principles of a bat box.
- be made from untreated wood, ie wood that has not been pressure-treated with chemicals. Bats are sensitive to smells and preservative chemicals may be harmful to them
- be made from rough-sawn wood (rather than smooth, planed wood)
- have good, tight joints – bats hate a draught
- have a narrow slit at the back of the box, with a rough piece of wood leading up to it that they can clamber up.
- The very best bat box is one with two or more internal compartments, and one that is as large as possible – a deep cavern makes bats feel really safe and keeps the air temperature more constant
Make sure you have the right wood.
To make your own bat box, get hold of some untreated, rough-sawn wood. That can be easier said than done! You will probably need to go to a saw yard rather than a timber merchant, as you’re unlikely to find it at a DIY store.
Make sure you look for the Forest Stewardship Council (FSC) logo.
If your wood feels too smooth, roughen it by dragging the teeth of a saw across the surface – this helps bats get a good grip as they clamber around their new home.
Building your bat box.
You'll need a sheet of timber 15cm wide by at least 1.1m long, as thick as possible to keep the bats insulated from too much cold and heat inside (ideally 1.5cm or more).
Note: the dimensions shown are for 20mm thick wood. If your wood is different to that, the dimensions of the Base should be 150mm by 130mm minus 2 x thickness of the wood, e.g. if the wood is 18mm thick, the base should be 150mm x 94mm.
Mark the wood with a pencil, according to the diagram, and then cut it in to the sections.
Nail all the pieces together as shown in the diagram, making the joints as airtight as possible.
Choose your location.
You could put it under the eaves of your house or, if you have a large garden, on the trunk of a mature tree. Look for a spot that is at least 3m (10 feet) from the ground, sheltered from strong winds and exposed to the sun for part of the day. Position your box so it faces between southwest and southeast. Make sure there is a clear flight line in. Some foliage around the box will encourage use, such as climbing rose or honeysuckle.
Now put your bat box up.
Drill holes at the top and bottom of the backing plate and fix to the wall with screws or plugs. If you’re fixing it to a tree, you can use adjustable ties so you don’t cause any damage to the tree. If you don't have these, use stainless or galvanised screws or nails.
All bats and their homes are protected by law
So it’s important you don’t disturb them. Watch and enjoy from a distance. If you don’t see any bats going in or out, look out for their black droppings underneath the entrance. They’re little dry pellets that crumble to dust. The most likely new residents will be pipistrelles - there are two very similar species which are widespread in villages and towns.