Bats play a crucial role in our ecosystem, acting as natural pest controllers and pollinators. Building a bat house is an excellent project that helps local bat populations and contributes to a healthier environment. This guide explores the benefits of bats and walks you through constructing a bat house. In the video, This Old House general contractor Tom Silva demonstrates how to build a bat house with host Kevin O’Connor and landscape contractor Jenn Nawada.
The Importance of Bats in Your Backyard
Bats are often misunderstood creatures, but they provide numerous benefits to our environment and daily lives, including:
- Natural pest control: Bats are nature’s most effective exterminators, feeding on flying insects like mosquitoes, moths, and beetles.
- Pollination services: Many bat species use echolocation and their keen sense of smell to locate night-blooming flowers. As they feed on nectar, they move from flower to flower, promoting cross-pollination. They’re especially useful in pollinating agave plants.
Preparation Before Building a Bat House
Gathering the correct materials and tools is necessary before you start your bat house construction journey.
Materials
These are the essential materials you will need:
- Bat house plans
- Cedar or untreated 2×4
- Non-treated CDX plywood (3/4-inch exterior grade)
- Caulk (exterior-grade adhesive)
- Exterior-grade pocket screws
- Water-based exterior-grade black paint
Tools
Equip yourself with these tools to ensure a smooth building process:
- Tape measure
- Miter saw
- Track saw or table saw
- Power drill
- 3/4-inch drill bit
Selecting untreated wood for your bat house is vital, as chemicals in treated wood can be harmful to bats. Cedar is superior due to its natural resistance to decay, though it may be more expensive than standard lumber.
Step-By-Step Guide To Building a Bat House
Follow these steps to construct your bat house:
Cut the Side Pieces
- Use a miter saw to cut the side pieces from the 2×4.
- Set the saw to a 20-degree angle and cut both ends of the board.
- Measure 21 inches between the angled cuts and make a square cut.
Cut the Plywood Sheets
- Cut the plywood sheets for the front, back, and interior partitions.
- Ensure the interior partitions are about an inch shorter than the front to allow bats to move freely.
Create a Bat Ladder
- On the back piece, cut shallow grooves across the bottom.
- This will provide a surface for bats to grip as they enter the house.
Dry Fit the Pieces
- Ensure proper alignment by dry-fitting all the pieces.
- Start with the back piece, then add the side pieces, followed by the interior partitions and front piece.
Mark and Pre-Drill
- Mark the locations for fasteners.
- Pre-drill holes to prevent splitting.
Apply Caulk and Fasten
- Apply caulk to the front and back of the side pieces before fastening them to the front and back panels.
- Secure the interior partitions with screws.
Attach the Roof and Drill Ventilation Holes
- Attach the roof pieces using caulk and screws.
- Drill ventilation holes in the sides of the bat house using a 1/2-inch drill bit to promote airflow.
Paint the Bat House
- Paint the exterior of the bat house with water-based, exterior-grade black paint.
- This helps absorb heat and keep the bats warm during the day.
Proper Placement of Your Bat House
Proper placement of your bat house is critical for attracting bats and ensuring their comfort. Consider the following guidelines:
- Height: Mount the bat house at least 12–15 feet above the ground to protect bats from predators.
- Sun exposure: Choose a location that receives at least six to eight hours of direct sunlight daily, preferably morning sun.
- Proximity to water: Place the bat house within 1/4 mile of a water source, such as a pond or stream.
- Clear flight path: Ensure there’s an unobstructed area below and in front of the bat house for bats to easily enter and exit.
- Building attachment: If possible, mount the bat house on the side of a building rather than a tree, as this provides more stable temperatures.
Maintaining Your Bat House
Maintaining your bat house is essential to keep it in good condition and attractive to bats:
- Annual inspection: Check annually for any damage or wear and repair as needed.
- Periodic cleaning: Clean out the bat house every few years during the winter when bats are not present.
- Monitoring: Monitor for signs of occupation and avoid disturbing the bats during their active season.
Additional Considerations for Bat Houses
While building a bat house is a straightforward project, some additional considerations can enhance its success and longevity.
Choosing the Right Paint
The choice of paint can impact the durability and attractiveness of the bat house. Water-based, exterior-grade black paint is recommended for its ability to absorb heat, keeping the bats warm during the day. Avoid using oil-based paints, which can release harmful fumes.
Insulating the Bat House
Insulation can make the bat house more comfortable for its inhabitants. Adding a layer of foam board insulation on the inside of the back panel can help maintain stable temperatures. Ensure the insulation is securely attached and does not block the ventilation holes.
Seasonal Adjustments
Bats’ needs may change with the seasons. During colder months, they require more warmth, while in warmer months, overheating can be a concern. If possible, consider placing the bat house in an area that gets plenty of sunlight during the fall and winter and some shade during the summer.
Resources
You can support these beneficial creatures by providing bats with a safe haven in your backyard. For the building materials, Silva chose 3/4” exterior grade CDX plywood and 2×4 cedar board.
He used a miter saw to cut the cedar board and a track saw to make all the other measurement cuts on the CDX plywood. To give the bats a better area to grip, Silva used the track saw to cut a few rows of grooves on the bottom of the back piece.
To assemble the bat house, he secured the pieces with caulking adhesive and exterior-grade pocket screws. He then used a drill bit to create venting holes, allowing better airflow. For the finishing touch, the team painted the bat house with exterior-grade water-based black paint.
