Sat. Mar 2nd, 2024
Park staff after installing bat house

Today’s post comes from Rachelle Law, Discovery Leader at Sleeping Giant Provincial Park.

Are you looking for a fun project you can do yourself this summer?

Would you love to find a solution to the number of annoying mosquitoes in your backyard?

Are you passionate about creating habitats for wildlife?

If you answered yes to any of these questions, this blog is for you!

Park staff in front of the bat house

This year, Sleeping Giant Provincial Park needed a new bat house to provide habitat for bats in the park. We take on the challenge of building ours!

Why build a bat house?

Our new bat house will help us monitor the health of the bats and the populations of several species found in the park. Here at Sleeping Giant, we are passionate about protecting, researching and monitoring the park’s diverse wildlife.

A bat house can:

  • Help keep mosquito populations low on your property, as bats love to eat mosquitoes. In fact, some little brown bats can eat up to 1,000 mosquitoes per hour!
  • Provide alternative habitat to prevent bats from living in your attic or other parts of your home.
  • Help bat populations in your area that may be declining or struggling due to white-nose syndrome, habitat loss due to deforestation, and pesticide use.

Bats play many important roles in our ecosystems, including helping to pollinate, spread seeds, and control pests. They are also an important part of the food chain.

For more information about bats in Ontario and their importance, click here.

Where should your bat house go?

Your bat house should be placed in a location where it receives at least eight hours of sunlight, preferably facing south.

Bat house attached to a building

It should also be:

  • installed 10-20 feet above the ground
  • about 300 meters from a water source
  • in a place free of light pollution

Make sure the front of the bat house is free of obstructions, including anything that could block the bat’s entry or flight path.

Place it on the side of a house or other structure such as a pole. If you install it in a tree, make sure there are no branches under or above the bat house, as bats need a lot of space to enter.

Building your bat box

*Safety Reminder* Be sure to use proper protective equipment (like safety glasses!) when building your bat house. If you’re new to projects like this, ask a more experienced friend for help!

Step one: Gather your materials. Will need:

  • 1/2″ thick exterior grade plywood sheet
  • 1″ x 2″ wood slats
  • black or brown water-based exterior paint or stain (non-toxic)
  • exterior grade screws
  • paintable silk latex chalk (if it’s not in a squeeze tube, you’ll need a caulking gun)
  • sandpaper or sander
  • cloth or rag
  • electric drill (with necessary bits) or screwdriver
  • Hole saw attachment for holes with an approximate diameter of 1 1/2″
  • support to attach the bat box to the tree
  • roofing shingle attached with roofing nails (optional)
  • measuring tape
  • paint brush or roller
  • table saw (or ask the hardware store to cut the wood for you)
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Second step: cut your wood.

You can make your bat house any size, but make sure it is at least 20″ tall and 14″ wide. The larger your bat house is and the more chambers it has, the more bats will be able to roost. Having extra space can help bats raise more young.

Table saw ready to cut wood.

You will need to cut:

  • a roofTable saw cutting wood
  • two side pieces with angle for the roof
  • a front panel made of two separate pieces (a taller top piece and a shorter bottom piece with a 1/2″ ventilation gap)
  • bat roosting chamber(s) (at least one, but the more the better)
  • Back panel of the bat house (this should be the longest piece, as it should have enough room for a 4″ to 6″ landing platform for the bats. This allows the bats to swoop down to the landing and climb into their homes more easily)
  • wooden strips to place between each panel of the bat house

Wood strips should be at least 3/4″ to 1″ thick to provide adequate space for bats to sleep. Little brown bats need 3/4″ and big brown bats need 1″ of space.

Pieces of wood for the bat house.

Here are the measurements of the bat house we built:

  • ceiling: 26 1/2″ x 8″
  • top front piece: 24″ x 18″
  • bottom of front piece: 24″ x 6″
  • space between top and bottom of front piece: 1/2″
  • back: 24″ x 32″
  • Landing pad: 24″ x 5″
  • break chambers: 24″ x 24″
  • wood strips to separate chambers: 2″ x 24″ (must be at least 3/4″ to 1″ thick)
  • side pieces: 4 1/2″ x 27 1/2″ with a 30 degree angle

Step three: Cut notches in the plywood on the back of the bat house and roosting chambers.

Collage of wooden photos with notches.

This can be done using a table saw, circular saw, paint scraper, knife, or chisel. The notches can be 1/32″ to 1/16″ deep and be sure to leave a 1/2″ gap between the notches.

We use a table saw to cut the notches by lowering it just enough so that it cuts grooves in the wood without cutting it all the way through.

The notches mimic tree bark and allow bats to grip and move around your home properly.

You can also use plastic mesh for the landing chambers, but it will not be as durable as wooden notches and you may need to replace it annually.

Step four: Drill holes in the bat house chambers.

Drill with piece of wood for bat box

Use a hole saw as a drill. Holes should be at least 1.5″ in diameter. Drill holes only in the chamber parts and not in the front or rear walls.

Place holes near the top of the chamber walls. This will help keep the bats warmer during cold weather.

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These holes will provide a way for bats to travel from chamber to chamber within your home.

Step five: Build your bat house!

Bat House Assembled with Notches

Be sure to use exterior screws to assemble your bat house. You should also pre-drill the holes to ensure the plywood doesn’t crack.

Use the wood strips to space out the layers of the bat house. Make sure the wood strips are at least 3/4″ to 1″ thick to provide enough room for the bats.

Assembled bat house

Make sure you line up the pieces so you have enough room for the roof and landing pad.

Step six: Apply exterior paintable latex caulk.

Apply it to any cracks in the bat box or places where you think rain may leak. Caulking the edges of the roof is especially important. The caulking will help keep the bats warm and dry inside.

Read the caulk product label to see how long it will need to dry. After it dries, it’s time to move on to the next step.

Step seven: Prepare the bat box for painting or staining.

Use sandpaper or a sander to sand the exterior of your bat house. After sanding, use an old rag or cloth to remove dust from the exterior.

Step eight: Paint or stain your bat house.

You must use water-based exterior stain (non-toxic).

Paint can in front of assembled bat house

The paint or stain should be dark to reflect the temperatures of the area where you live. The colder the climate you live in, the darker your bat house should be. Dark colors attract sunlight and heat, which helps keep bats warm.

Let the paint dry for the recommended time found on the product label.

Bat house painted black

Step nine: Set up your bat house!

Place a bracket on the back of the bat house or use another appropriate method to secure it to the desired surface.

Park staff after installing a bat house

Find the best place to place your bat house. Remember to check the guidelines we mentioned above on where to place it.

Where you place your bat house will affect the likelihood of bats moving into it, so make sure it is in a good location.

Now what?

The fun doesn’t have to end after completing your bat house!

Park staff holding bat house

Here are some cool things you can get involved in next:

  • monitoring projects: Join the “Help The Bats” project on iNaturalist with the Canadian Wildlife Federation here
  • Observation: Enjoy watching your bats at night. This is a great activity to do with family and friends, especially children and young people, to get them excited about the natural world.
  • share with us: Tell us about your experiences building your bat house on social media. Tag us in your photos @ontarioparks!
  • Be respectful: Bats don’t like to be disturbed, so only check your house for bats when necessary or in need of repair.

Good luck building your bat house! We thank you for your contribution to the protection of bats and the provision of essential habitats.