Building A Bat House

What I have built is a place for REAL bats to take up residence in the wild, not a piece of finely crafted garden decor.

Bat houses are very simple. Bats will live in caves and inside a wall, how complicated can it be? There are dozens of websites with plans for bat houses on the internet but I found the article "Efficiency of Bat Houses" by M.J. Pybus - Alberta Environment, to be the most useful source of general information about building one. I think you should understand why they are built the way they are and what the necessary components are, in order to build a successful bat house. Following are a few important points that I have learned:

• The interior surfaces must be roughened to give the adult and baby bats something to hold onto. Many directions say to line the inside of the bathouse with nylon screening for this but I have some doubts about the safety of screening. I have seen too many tiny creatures caught in small fencing and screening.


• The 3' tall bat houses are the ones used most often.


• The cavities can be from 3/4" to 2" but the opening should be only 3/4" to prevent predators from entering. My bat house is 3' tall and the spaces are 3/4" thick. I don't think the width of the house matters much.


• Old wood is best. The bats will wait a year until it is aged in the weather if you use new wood. It can be artificially aged by rubbing it with mud. Bat guano is apparently great for this, too. (Uh...I don't think I'll be going there.)


• The bathouse needs to be mounted about 15-20' off the ground, in the sun and not near trees with branches to get in the way of direct flight. A post is better or an old TV antennae, like I have.


• In the north it should be painted black, with non toxic latex paint, to absorb the heat. In the hot south it should be painted white to reflect the heat.


• When mounted it should tilt back about 10 degrees. This will cut down on the percentage of babies that fall out.

After a lot of research I have decided that I am ready to start building. I have been collecting the materials for months with this planned as one of my many winter projects. This one has to be completed and in place before the bats return in the spring.

With the addition of my new radial arm saw (I love power tools!) I am on my way.


First thing this morning, after opening the hen house door, turning on their light and waking them up, (Good morning, Ladies and Gent!) I went to the shop and began pulling out the wood.

















I decided, after some thought to make it 3' long and 18" wide with the required 3/4" gap for the cavities. I gathered the pieces of wood from the pile and cut them to the correct sizes. Here is the pile of 18" wide cross pieces and 1" x 3/4" framer pieces which are 3' long. I am fortunate enough to have aged framer pieces. I will have to artificially age the cross pieces with dirt. I will leave it outside for the remainder of the winter to help age the wood, as well. I hope to have it mounted the same week it is finished, if there is time for that. Yes, my shop table is BLUE (not my doing.)

Before putting it together I have to roughen the inside walls of the bat house. I looked at all the tools I had for this and started with a raster on the drill, didn't work very well. I then switched to a large bit, also not very good for this. After trying a few things, I settled on the claw of a hammer. It worked the best. I covered one piece with holes, then turned it upside down and did it again, slanting the other way, so there are crevices for the bats to hold onto going up and down. Finally I had each piece covered with dents. The interior pieces needed to be done on both sides. This turned out to be the most tiring and time consuming part of the project.

These are the inside pieces after rubbing dirt on them to age them. I used a large hand brush for this instead of a cloth. I should have used muddy water as it would have soaked in and filled the crevices, but I didn't. (Hindsight is a wonderful thing.)

Now that the individual pieces are finished, it is time to put it together. While I prefer to work with screws, I used 3" nails for this job. Obviously 3" is not long enough for the entire depth of the house, which has two large cavities, each 3/4" side. I nailed it together in stages. I put one nail in each board to hold them in place. After it has all been put together, I will put in two nails, in each side of each board, on the outside. In the above picture they are not yet nailed or aged. I am just putting them together to make sure it all fits.


This is the basic house, before it has all been nailed together.

The underside of the top piece needs to be roughened and aged, as well.

Basic completed and nailed bat house. It will need a slanted roof piece to keep the rain and snow out. Some internet sites recommend sealing the cracks on the outside to further help keep out the weather. I have also read that it needs air circulation so that it doesn't build up too much humidity from the bat bodies. I am not going to seal it, as I don't think this one needs it, but I do have some scrap shingles that I may tack on the back which will be facing north. I will add them IF I can find them under the snow. I was using them to line the flowerbed but can spare a few to help keep the bats warm and dry.


I already have bats that have made their home for two summers inside the wall of my house. It's these bats that I don't want to lose when I seal them out this spring so I am going to put this bat house near by, on the unused TV antennae attached to the house in the back yard.

Now to put the back piece on to use for mounting it on the pole, or wherever you are going to put it. Mine is going up there.

I tried several mounting methods and settled on this one in the picture below. (It worked very well when mounted!)


I added a piece at the bottom to give it the desired slant to help keep the baby bats in the house.

This is the finished product. It is a large bat house and will hopefully hold many bat families. Obviously it is not a piece of garden decor but has been built solely with the requirements of the bats in mind. No one will see it up there. I may still run water into the cavities to soak the mud into the wood and help age it before it is hung in place. If I can find the shingles, I will put those on the back, as well.

I have mounted it on the antennae here, near the ground, just to test the mounting method. One of us will climb up there and put it in place after work today. (It won't be me. I don't do heights.)