How to Make a Kent Bat Box - Step By Step Instructions
Kent Bat Box Construction Sheet - Kent Bat Group
With the busy part of this years' season behind us, I finally found an opportunity to do something I've been meaning to do for years but never quite found the time to do... having a bash at building a Kent bat box. However, before I gallop on with remainder of this blog, for those who have not encountered a Kent bat box before and are curious as to what makes this type of bat box unique, it's essentially a bat box comprised of planks of rough and/or roughened untreated wood that are laid over narrow batons to create one or more sheltered narrow crevices that are used by bats for roosting. When you know what to look for, you'll commonly see these boxes in country park, nature reserves or any other places where a group of people or an organisation have built their own boxes.
From a personal perspective, my first 'up and close' encounter with a Kent bat box was during my Bat Skills Development Program training with Neil Middleton at BatAbility. Neil uses a Kent bat box to demonstrate the best way in which to check a bat box of this type for roosting bats, where the use of an endoscope and/or inspection camera is required. It was during this training session that I came to appreciate the simplicity of the Kent bat box, in terms of providing an ideal home for crevice roosting bats such as pipistrelles.
There are many different types of Kent bat box designs available on the internet, in addition to various pre-made models that can be bought from companies such as Wildcare or NHBS. However, for a DIY savvy person like myself, where is the challenge and fun in buying one that is pre-made? So, after a quick trawl on the internet, I decided to try and build a box based on a design published by Kent Bat Group; details of the box design can be downloaded via this link. One of the great things about the Kent bat box design is the fact that it's completely forgiving in terms of dimensions. In fact, you can make each compartment as long or as wide as you want. However, most of the boxes out and about in the countryside tend to adhere to rough dimensions as published by the Kent Bat Group.
Having told my husband that "I would be making a bat box today", I headed down to my local timber merchant to see if I could find any wood for the box. However, unless your timber merchant is pro-wildlife, then it's unlikely they will be able to confidently tell you whether or not their rough cut wood has been pre-treated with a preservative. I decided the err on the side of caution and selected two finished timber planks that were definitely untreated, which were more expensive than the treated rough sawn planks. to be fair, with a little bit more foresight, it would have been better to have contacted a sawmill direct for the untreated wood but the dressed wooden plank would suffice in this instance.
I actually ended up making two boxes with the wood I bought. The smaller of the two boxes is 53cm in length, with the little (front) compartment measuring 25 cm in length and the longer back compartment measuring 55 cm in length. The longer boxes is 82 cm in length, with the front compartment measuring 55 cm in length and the longer back compartment measuring 67 cm in length. The width of both boxes was determined by the overall width of the plank is had selected (22 cm).
To make the box you start by marking off the relevant sections on your plank (note: I was quite lucky because I only had to use one single plant). However, remember that if you use a shorter plank then you will need more than one plank to complete your box, so it helps to plan in advance. Once your plank is marked off, take a hand saw and carefully cut your box panels and batons out from the overall plank. However, before moving onto the assembly stage, it's important to rough-up your wood so that bat will be able to land and find purchase to climb up into the box. Once this task is completed you can then move onto assembling your box, as illustrated in the photographs below.
Start by laying your longest panel on a work bench and place the two longer batons along either side, flush with the sides of the panel, as illustrated in the photograph above. Once complete, lay your second largest panel on top of the batons and secure using a clamp (note: this is optional). To save on drilling and screwing, I opted to use a screw that was long enough to go through both the second panel, the underlying batons and the back of the box. Regardless of the length and number of screws you use, I would always recommend pre-drilling the holes to avoid cracking the timber, especially when you are screwing so close the edge of the panels. Once complete, you then repeat the same process for the smallest panel and shorter set of batons.
Having assembled the main part of the box, you then need to secure it with a roof and a second set of batons to brace the box against a wall or tree. In order to provide a draft free box, I decided to re-cycle some old packaging foam I keep to one side for such projects. The foam was soft enough to provide a cushion between the roof of the box and the two compartments below. Having tacked the foam in place, all that remained was to position the roof correctly, pre-drill four screw holes, screw the roof down and then trim any excess foam, as illustrated in the photographs below.
For the larger Kent bat box, I essentially repeated all of the above steps, including installation of the foam draft excluder under the roof of the box. However, due to the length of the panels required for the larger box, I used a bench saw to cut the batons and panels, although a hand saw would still have produced a perfectly acceptable result. I also realised between making the first (shorter) box and the second longer one, that I should have roughed up the wood a lot more, as can been seen in the photographs below, so on that basis, I completed a retrospective extra precautionary roughening of the smaller box!
The next challenge was finding a way to hanging the boxes! Due to the likely future location of the boxes (on the side of a building), I decided against hanging each of the boxes using heavy duty wire, which was mostly due to astatic reasons. Instead, I decided to use a heavy duty screw covered with a silicone sheath, which was designed to sit within a metal eyelet (secured to the wall of the chosen building using an accompanying rawlplug) rated for a 12-kg load. The purpose of the silicon sheath was to prevent the screw from removing the protective plastic coating on the metal eyelet and to provide a snug fit within the eyelet. As can be seen from the photograph below, I also fitted a metal bracket over the top baton to reduce the likelihood of the screw shearing away from the baton over the coming years. One word of warning, whatever mounting system you adopt, make sure it is strong enough to bear the load of the box relative to the anchor point, and remember, if in doubt, seek the necessary professional advice!!!
I hope this blog inspires others to make their own Kent bat boxes because they are really easy and quick to make. In addition, given the simple design of the box, the project would make a perfect activity to do with children, although I would recommend children are always supervised!
This blog was written by Graham Sennhauser. Graham is TETRIX Ecology’s Principal Ecologist and is a licensed bat consultant / licensed bat worker based in Glasgow, Scotland. He would be more than happy to respond to any questions in connection with his blog or wider-ranging bat-related queries. You can learn more about Graham's background via his profile page or contact him on the following email address: graham@TETRIXecology.com.