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The habitat of native bats is threatened. Trees are being cleared and buildings are being built ever more densely. It is therefore worth building bat boxes to preserve the species. We explain how it works.

In a nutshell

  • Rough sawn and untreated wood offers the animals an environment that is as natural as possible
  • the right dimensions make the dwelling attractive to bats while keeping birds and other "guests" away
  • Tightly built and draught-free, the chances of acceptance of the dwelling are best

What is important with the bat box?

The goal of a bat box is for the animals to accept the shelter and feel comfortable there. In order to achieve this, the artificial cave must meet a number of basic requirements, which also determine the later construction:

  • Entry gap between 20 and 25 millimeters wide (too wide: intruding birds, too narrow: no access for adult animals)
  • tapered interior: offers animals of all sizes opportunity for abdominal and back contact with cave walls (often preferred as a sleeping place)
  • Draft-free construction through dense joints, as there is a general rejection of drafty quarters
  • Creation of surfaces that are easy to walk on thanks to rough-sawn wood
  • Avoiding any contaminated building materials, as well as varnishes, paints, glazes, etc. (high sensitivity of the animals to environmental toxins)

Step by step to the bat cave

If we transfer these essential requirements to the planned nest box, the result is the following step-by-step instructions.

The material

  • untreated, rough-sawn wood, board thickness at least 20 millimeters
  • Roof battens 20×40 millimeters, rough sawn and untreated
  • Wood glue, waterproof and solvent-free
  • Roofing felt + associated roofing felt pins
  • Screws + dowels for assembly, e.g. 6×100 and 3×40

Tip: For a planned location for the bat box outdoors, use more durable hardwood such as beech or oak. Boxes for more sheltered locations can also be easily built from less durable softwood.

tool

  • Table or hand-held circular saw with inclined position of the saw blade
  • Cordless screwdriver with suitable holder for screws
  • hammer
  • screw clamps
  • Pencil, ruler / protractor
  • Wood drill set, suitable for cordless screwdriver

Step 1 - The Cut

First of all, cut the individual parts for the bat box out of the wood:

  • Rear wall height x width = 450 x 250 millimeters
  • Front wall height x width = 350 x 250 mm
  • Roof depth x width 110 x 310 mm

Now the conically tapering sides follow from the roof battens in order to achieve the desired rejuvenation of the inside of the box:

  • Length 250 mm, thickness 20 to 40 mm (cut from 40 mm page)

Finally, you need the floor, which you also create from a roof batten:

  • Length 210 millimeters, height approx. 20 to 30 millimeters with sloping saw edge (cut from 40 millimeter side)

Step 2 - The Body

Now assemble the body of the bat cave and glue the individual parts over the entire surface to achieve an airtight joint of the individual parts:

  • Glue the side panels with the 20 millimeter side up to the outer edge of the rear panel
  • Upper edge of side panels flush with upper edge of rear wall
  • through thickening of the sides downwards, later widening of the interior downwards
  • Place front with flush top edge on side panels and glue
  • Glue the base flush with the bottom edge on the inside of the body lid
  • let the sloping side point upwards (towards the inside of the box).

Tip: Press all the glued joints firmly together with the screw clamps in order to achieve a flat bond without later defects. This way you avoid unwanted drafts inside.

Step 3 - The Roof

Complete the body of the bat box with a roof that you slope slightly for better drainage of rainwater:

  • Level the top of the body with a circular saw, tilting the saw blade (stronger cut back on the front of the body for roof pitch forwards)
  • Put the roof on and glue it, putting the rear edge flush with the rear wall
  • lateral and front overhang around 30 millimeters each

Step 4 - The Completion

Finally, some remaining work is still missing to actually make the new housing ready for use:

  • Screw the roof batten with the 40 millimeter side onto the rear panel
  • Alignment vertical, location in the middle with equal distance to the sides
  • Overhang above and below about 5 to 7 centimeters
  • Screw connection with at least 3 screws 3×40 millimeters in the rear wall
  • Pre-drill the overhangs with an 8 mm wood drill bit for later assembly
  • Cover the roof with roofing felt, fold the cardboard over the sides of the roof and nail it down with roofing felt pins
  • Cut off the cardboard that is protruding below

Step 5 - Hang properly

The grand finale is now hanging up your new bat box:

  • align vertically
  • screw to the substrate, e.g. house wall or tree trunk, via holes in the roof batten
  • If necessary, pre-drill the subsurface and insert dowels

frequently asked Questions

What is the optimal location for a bat box?

The new bat cave is designed to provide protection from predators and the weather. The optimal location is therefore at a sufficient distance from the ground and ideally not on the weather side of the house to avoid driving rain. Bats love warmth, so even sunny locations are not a problem. For example, house gables or sufficiently tall trees are well suited.

Is the rough-sawn wood sufficient to give the animals enough support?

Bats have no problem clinging to natural wood with their claws. If you want to offer the animals additional help, you can use a circular saw to make horizontal cuts a few millimeters deep on the back of the box before assembly.

Can a bat box be accessible to other animals?

The bat cave is designed in such a way that cats, martens or other predators, for example, cannot get inside. However, bats avoid dwellings whose access routes are heavily frequented by predators. It is therefore better to choose locations at a height of around 2 meters or more.

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Category:

Garden design