How to Seal Your House Against Bats - Materials, Tools

What Are The Most Common Bat Exclusion Devices And The Most Common Materials Used To Seal Buildings?

Exclusion Devices
1/4 inch poly netting - a good all-purpose bat net with a small enough grade to prevent the bats from getting stuck in the mesh or strangled. It must be set correctly though, to allow the bats to fly out but not fly back in. Making this shape right is an art, like sculpture.

Screen - yes, regular window screen at home depot, the softest you can find, makes a great exclusion tool. As with the netting, a combination of staple gun or duct tape is a good way to secure it to the house.

Funnels - funnels made of various materials, from clear plastic to 1/4 inch steel screening, work very well in some scenarios.

Batcones - these are special funnels with a tapered body and attachment wings that you can purchase online.

Seal-Up Products
Polyurethane Foam - the Great Stuff in a can that you can buy at Home Depot or Lowe's is a type of this foam. But I use a higher-density product, dispensed from a professional foam gun with flow control. It is also black, which is far less visible than the off-white Great Stuff, which cures to become orange over time! It looks bubbly and ugly. Never use this foam at a time or in an area where bats can come into contact with it before it dries and hardens, or else it will get on the bats and possibly kill them.

Caulk - regular caulk of many kinds can be used to seal the gaps in a building - an all-weather rubberized kind is best

Screening - staple or screw steel screening over gaps.

Netting - in some areas, that 1/4 inch poly netting works great, such as when you have to stuff gaps between barrel tiles on a roof.



If you have a colony of bats living in your building, there are a number of exclusion devices that can be used to prevent them from entering the building. Once the bats have been completely removed, or after they migrate for the winter, there are several types of materials that can be used to seal the building so that the bats will not be able to enter. One important thing to note is that exclusion and sealing cannot be performed during the summer when there might be flightless baby bats in the roost. Exclusion will prevent the adult bats from entering the building, but the babies will still be inside.

When To Exclude
It is both illegal and inhumane to trap the babies inside and prevent the mothers from being able to take care of them. In addition, your problems will be worsened when the babies crawl out of the roost in search of food, and they end up all over the interior of the building. Determine the species of bat so you will know exactly when there will be no flightless babies for that species. Typically, female bats will give birth in the spring, and the babies will be old enough to fly by the end of August. That excludes April through August for bat removal and building sealing. Then you can perform the exclusion and the sealing when it is legal to do so.

Check For Entry Points
Your building could have several bat entry points, so you will first determine all of the possible areas they’re getting in. If you miss even one, the bats will be able to get back in. Even when they migrate, bats usually return to the same place each spring. If the building is completely sealed off, then they will be forced to find a new place to live. Common entry points include ridge caps, louvers, vents, and fascia boards.

Any damaged areas of the building should be examined, such as where windowpanes are broken or missing, warped boards or siding, missing bricks, or any type of small gap or opening. The bats only need a gap of 3/8 of an inch to enter. You should also look for signs that could indicate the entry point, such as piles of guano (droppings) on a particular wall or area of the roof and a large amount of urine stains in one area. Once the potential entry points have been determined, you can place exclusion devices on each one.



What Are They Made Of
Exclusion devices are designed to allow for one-way travel only. The bats will be able to exit through the device, but they won’t be able to return through it. This is a humane removal method because the bats are not harmed as they exit the device; they will only be inconvenienced, as they will have to find a new home. Materials used in exclusion devices vary. Some are made from pipe, such as a common PVC pipe. Others use netting in which a one-way valve is installed. Other devices are funnels or cones that prevent the bats from getting back in.

Possible Problems
Regardless of the material that the device is constructed from, the key is that it must have a one-way flap or valve installed on it so that the bats can leave through it, but they can’t get back in. Once the devices are installed, the bats’ exit will have to be monitored. Depending on the type of device, different things can go wrong. For example, a bat’s wing might get stuck on the netting, and it will block the path of the other bats. Sometimes the bats are apprehensive about leaving through the device, but they will eventually because they must feed. The devices must be left in place for several days, as the bats might not all leave the first night. Once you are certain that the bats are all gone, the entry points can be permanently sealed off.

Location And Material Go Together
Depending on where the entry points are located on your building, different materials will be used. Some entry points can be sealed using a commercial sealant, such as caulk, foam sealer, and polyurethane sealants. These are squeezed into all of the little cracks and gaps, and when it dries, the area will be completely sealed off. If the entry point is a loose board that is not warped, it can be nailed down to tighten it. If the boards are warped, you may have to both nail and use a sealant on it to close the gap.

Fascia boards can be tightened by drilling metal bolts through them and into the concrete. Some entry points are best sealed using netting. Netting is typically made from polyurethane, and it can be cut to fit. You can place netting over vents and other areas that can’t be completely closed off. Metal mesh netting can also be used to seal areas of the building that can’t be caulked.

HELP: If you need professional help in solving your bat problem, please click on my Hiring Advice and 2017 Directory of Bat Removal Professionals serving every city in the USA.

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Big Brown Bat
catch bat flying inside house
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Little Brown Bat
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Will a pest control company remove a bat?
How to get bats out of a wall
How to keep bats out of a barn
How to get bats out of the attic vent

Wildlife Education - Information and Advice for the Safe Removal of Bats from Attics