Building a Simple Bat Box for Woodland Edges

By Identifying Common British Trees by Their Bark
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27 Aug 2026

Building a Simple Bat Box for Woodland Edges

Why Woodland Edges Suit Bats So Well

A woodland edge — the boundary where trees meet a hedge, a ride, a meadow or a garden — is one of the busiest places in the countryside after dark. Sheltered from wind, warmed by the sun through the day, and thick with the midges, moths and beetles that bats hunt, it offers both food and a safe line of travel. Bats will often follow the same edge night after night, using it as a corridor between roost and feeding ground.

What many of these edges lack is somewhere to roost. Old trees with rot holes, loose bark and cracked limbs have become scarce, and many of the gaps in modern buildings have been sealed. A simple wooden box, fixed high on a sheltered trunk, can fill that gap. It will not replace a veteran oak, but a well-made box in the right place can be occupied within a season — and common pipistrelles, our most widespread bat, are quick to take advantage.

Choosing the Materials and Getting the Dimensions Right

Use rough-sawn, untreated timber about 20mm thick. Rough surfaces matter: bats need something to grip, and a planed board gives them little purchase. Avoid timber treated with wood preservative, and never use creosote or paint inside the box, as the fumes are harmful. A little water-based preservative on the outside of the roof is acceptable but not necessary.

Back board: 450mm × 200mm × 20mm
Front board: 400mm × 200mm × 20mm
Two side spacers: 450mm × 25mm × 20mm
Roof: 250mm × 220mm × 20mm, plus a 250mm batten for the top edge
Galvanised screws, 40mm

The spacers sit between the back and front boards, creating a 25mm-wide crevice that runs almost the full height of the box. This single slot is what bats use, and it mimics the narrow gap behind loose bark. The base is left open — that is the entrance. Roughen the inside faces with a coarse rasp or a few horizontal saw cuts at 20mm intervals so bats can climb.

Assembling the Box

Screw the two spacers to the edges of the back board first, then fix the front board to the spacers, keeping the tops level and leaving the bottom open. Pre-drill every hole to avoid splitting the timber, and keep screw heads flush so nothing protrudes into the crevice. Add the roof last, sloping it slightly forward with the batten behind it to shed rain away from the entrance, and allow a small overhang at the front and sides.

Give the outside a quick sanding if you like, but leave the inside rough. There is no need for a base, a hinge or a baffle in a box this simple.

Siting the Box: Height, Aspect and Shelter

Position matters far more than a fancy design. Fix the box 3 to 5 metres up a mature tree, clear of the canopy so bats have a straight flight path in. Face it south or west where possible, which gives the box a warm afternoon and evening, but avoid a spot in full sun all day — overheating is a real risk in a heatwave. Shelter from prevailing wind and driving rain matters too, so tuck the box on the sheltered side of a trunk or under a light canopy.

Choose a tree at a woodland edge, hedgerow junction or along a ride.
Keep the entrance clear of branches for at least a metre.
Avoid positions above doors, windows or paths, where cats can wait.
Use aluminium or coated screws and check the fixing annually.

A box on a tree in a garden adjoining woodland will often do better than one deep inside a dark wood, because the edge is where the insects are.

Checking, Recording and Looking After the Box

Once fixed, leave it alone. Bats are protected by law in the UK, and that protection covers roosts even when the bats are absent — disturbing occupants or blocking an entrance is an offence. Never open a box to see what is inside. Instead, watch from a distance at dusk between May and August, or look for small dark droppings on the trunk or ground below, which are a sure sign of use.

Checking is best done with others. Many local bat groups welcome records from garden and woodland box schemes, and a shared count along a hedge or woodland edge quickly shows which boxes are working and which are not. Note the date, the weather, the time and how many bats you see leaving, and pass the record on.

Occupied boxes need very little maintenance. Repairs to fixings, and a gentle brush of cobwebs from the entrance once a year in late autumn, are usually all that is required. Where a box stays empty after two or three seasons, try moving it a few metres, altering the height or turning it to a warmer aspect before assuming the design is at fault.

Wildlife

Starting a Coppice Cycle in a Small Wood

Learn to identify woodland birds by song, from the drumming of woodpeckers to the fluting notes of blackbirds, and improve your wildlife surveys.

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5 Comments

Robert Sonny says Jul 21, 2024 at 10:00am

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Reply
- John Abraham says Jul 21, 2024 at 10:00am
  
  I must explain to you how all this mistaken idea of denouncing pleasure and praising pain was born and I will give you a complete account of the system
  Reply
  - Robert Sonnysays Jul 21, 2024 at 10:00am
    
    I must explain to you how all this mistaken idea of denouncing pleasure and praising pain was born and I will give you a complete account of the system
    Reply
Robert Sonny says Jul 21, 2024 at 10:00am

I must explain to you how all this mistaken idea of denouncing pleasure and praising pain was born and I will give you a complete account of the system
Reply

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