Bat Houses

Bat houses can help bats by providing shelter in areas that no longer have their natural roost structures, such as large, dead, hollow trees. Also, the bats in your area may choose to roost in a bat house rather than in your attic!   We will focus here on small-scale bat houses for homeowners, local parks, or community gardens. But much more is being done: parks such as Sun Lakes in Eastern Washington, for example, have mounted very large houses that attract thousands of bats. Bridges have been modified to provide bat habitat, and people have even created artificial caves for bats. Visit the Bat Conservation International website for details.

Our focus at Bats About Our Town is on basic bat house facts and on helping you position a bat house effectively so that bats will use it. For those who want to build a bat house, links are given for bat house plans.

Bat house facts for homeowners

• A bat house will not attract bats into your attic. If bats like your attic, they will already be there.
• If you wish to exclude bats already living in your home, but want to keep them nearby, you can create a bat house for them as an alternative living space. See Bat Encounters for information about bat exclusion.
• Bats will eat many, but not all, of the insects in your area. Predators never kill all of their prey or there would be no food for the next generation.
• Bats may also fly to popular feeding locations like Capitol Lake rather than staying by your home all evening.
• It may take several years for bats to find and use a bat house.
• All bat houses are closed on the sides and top, and open at the bottom, where the bats enter and exit. They contain partitions that are separated by 3/4 inches width, and NO WIDER. Any wider than ¾ of inch will only make it more attractive for wasps, but not bats.
• The best houses allow bats to move to cooler or warmer sections as needed.  

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Getting a Bat House

• Bat houses for outdoor use come in two basic shapes: a flat, rectangular box mounted on a building (NOT on a pole please), or a rocket-shaped box on a tall pole. Each type can work well in the Pacific Northwest.  The building creates thermal mass that moderates temperature swings.  The double rocket box model does the same, and allows the bats to move around according to the temperature they need.
• Indoors in an attic or barn, simply mounting boards the required distance apart (3/4 inch) is enough.
• Bat houses may provide just one chamber for the bats, or multiple chambers, depending on the number of boards used.
• The master site for bat house information is the Bat Conservation International website.
  • Free plans for a rectangular single chamber bat house.
  • Free plans for mounting a bat house on a pole or on a building.
  • Creative examples of indoor bat habitat construction.
  • For sale at 1-800-538-2287 or on the site: The Bat House Builder’s Handbook, a very thorough guide that includes plans for multi-chambered rocket box and flat box bat houses.
  • Bat houses are also for sale at this site. If you buy from another site, check that bat house against the BCI certification information to make sure you get a good design.

• Get free plans for a “rocket box” single chamber bat house adapted to the Pacific Northwest from Bats Northwest.  However, please note that the multiple chamber rocket box is much more effective, but you will have to buy the Bat House Builder’s Handbook to get the plans.
• You can also build a multi-chambered economy bat house or purchase a reasonably priced pre-made bat house. 

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Constructing your  bat house

1. Provide crevices that are ¾ inches wide and NO WIDER (wasps love the wider spaces and bats don’t).
2. Caulk the box so well you could carry water in it without dripping.
3. In the Pacific Northwest, paint the EXTERIOR ONLY with a flat black paint—three or more coats for lasting coverage. (Warmer or dryer regions need other painting strategies—visit the Bat Conservation International website for instructions.)
4. Make the house so sturdy and well caulked that you won’t have to check it every year.
5. Mount it on a pole or a building, not on a tree. Bats don’t like boxes on trees, which are vulnerable to predators and usually too shady.
6. Position it away from lights in the night (streetlamps for example).
7. Position it for maximum morning sun, east or south facing if possible.
8. Position it 15 or more feet in the air on a 4” x 4” pole or other strong support. Put something on the pole to prevent predators from climbing to the top.
9. On a building, position it so that predators such as cats and racoons cannot reach it.
10. Contact us with questions about positioning bat houses. 

Are bats using my bat house?

• Sometimes the bats are using a house as a night roost between feeding bouts but not sleeping there during the day. If so, you won't see them during the day. But you can check this by putting a piece of white plastic on the ground under the house and seeing if it collects any droppings.

Troubleshooting if bats are not using the bat house

• First, cross-check the list above about constructing your bat house. Make sure you are following all the guidelines.
• Bats About Our Town offers talks and consultations about effective bat houses. 
• Contact us to find out more.

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