Building a bat box gives them somewhere safe to roost, raise their pups and sleep during the day.
This Helping Nature activity can be completed as part of Schools Wild Challenge.
They should be made from untreated wood – wood that has not been pressure-treated with chemicals. Bats are sensitive to smells and preservative chemicals may be harmful to them.
The bat box should also be made from rough-sawn wood (rather than smooth, planed wood). It'll also need to have good, tight joints – bats hate a draught!
It'll need 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.
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.
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).
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.
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.