Bats on the Roof and in Roofing Tiles

By Chris Williams on February 13, 2015.

bat hanging in roofJohn Maher:  Hi, I’m John Maher, and today I’m here with Tim Chace of Colonial Pest Control. Tim is an entomologist and pest control technician. Today we’re talking about bats on the roof and in roofing tiles. Welcome Tim.

Tim Chace:  Good morning, John.

Signs of Bat Infestations on a Roof

John:  Tim, where would you look for signs of a bat infestation on a roof?

Tim:  Typically what they’re doing, John, is getting up under some kind of roofing material, in the little gaps there between the sheeting and the tiles itself. The little guys get up in there to spend the daytime in that discrete location. What we’re looking for generally would be the little rub marks where they’re getting up under a tile, or in fact, some of the feces or urine droppings in that area.

If you can picture a roof being up there on the top of a house, some of this material is going to actually fall down out of those little areas where the bats are roosting for the daytime. That material might accumulate on your front steps or the back deck. You notice that every day you clean it up, and there’s more of this material. That would be an indication that there’s someone living up on the roof.

John:  Right. You’d see in that space where the roof is kind of overhanging the sides of the house, and then it’s falling from there and dropping down, like you said, onto your deck, or something like that.

Tim:  If you had a gutter, or a gutter system, you might not notice these droppings coming down. That might collect that.

How and why do bats infest roof tiles?

John:  How do bats infest roof tiles, and why would they do that?

Tim:  Typically bats are looking for, again, a discrete, quiet location where they can spend the daytime away from predators, and things like that. Bats are very, very small animals, and they are able to actually penetrate very, very small openings.

A small brown bat can get into an opening a quarter inch by a half inch. That’s a pretty small little hole. What they’ll do is they’ll get up under the roofing tile, typically if you’ve got a ceramic roofing tile, or a shake roof, there’s going to be little gaps up underneath the tiles. They’ll just squeeze right up under there and spend the day.

What kinds of roofs are prone to bat infestations?

John:  What types of roofs? You mentioned the ceramic roofs and some shake roofs? Are there other types of roofs in Massachusetts and New Hampshire, or even in other places, that might be prone to bat infestation?

Tim:  Sure, sometimes you can think of a tin roof. There are these little gaps along the edges to get up under there. Maybe a slate roof would present nice little openings. Usually those are pretty tight, but again, the space that a bat can get into is very small. They just need a little bit of an opening to get up in under the tile, and they’re good.

Getting Rid of Bats in the Roof

John:  What do you think would be the best way to get rid of those bats, if they’re infesting your roof or your roofing tiles? Are you going to have to rip off the whole roof, or what’s the procedure there?

Tim:  That is a great question. Number one, we’re going to have to start with the design of the roof. A lot of bat problems, and other rodent infestations such as mice and rats, can be completely eliminated with a thorough construction plan.

Having your contractor know what you expect, as far as tolerances. Sealing up those little gaps at each roof tile sounds like an impossible task, but there are materials designed to do that, such as expandable foam. I’ve actually seen some little spacer devices that the tile sits on that seals that little gap.

It could be quite an undertaking, but there’s nothing that can’t be done if you want to do it. Basically, you’re looking at sealing up those little gaps as much as possible. Bats that are infesting roofing tiles are different than bats that are living within the structure. Your biggest concern there is the guano and urine falling out onto your exterior spaces.

It’s probably less of an issue than bats that are living inside the house. It’s still something that you want to address, if you’ve got concerns about bats. Another way to see bats, if you have a bat infestation on the roof, would be to wait just before dawn and just at dusk, to see if bats are actually leaving or returning to those areas. You can actually see them flying in.

John:  Those are the times when they’re the most active.

Tim:  Yes. It’s a little bit easier to see them at dawn than at dusk, because as it gets darker and darker, they are little black guys. You can actually see them against the lightening sky. They typically fly around for a few minutes before they enter the actual opening. You’ll see this little guy flying up, and then, “Oh, he’s gone. Where did he go?”

John:  It’s probably a good idea, even if you don’t have a bat infestation now, to maybe have your roof checked out and make sure you don’t have these gaps in between the roofing materials that would maybe create a nice space for these bats to live. Just make sure, like you said, talk to your contractor, and get those sealed up, so that you don’t have any issue.

Tim:  That’s correct. The best times to do any kind of bat exclusion work would be in the early spring, before the bats actually come back to your house. They’ve all left for the winter in most cases, and then that work can be done without harming the bats.

Again in the late fall, once the bats have actually left, that’s a great time to do it as well, so you’re not sealing any bats inside the house. Bats are beneficial organisms. They eat a whole lot of bugs. They do great work in pest control for crops. They’re really beneficial, so we really don’t want to kill the bats. We just want to relocate them to their natural habitat.

John:  That’s great information. Tim Chace, thanks very much for speaking with me today.

Tim:  Thank you, John.

John:  For more information, you can visit the Colonial Pest Control website at, or call 1‑800‑525‑8084. That’s 1‑800‑525‑8084.

Photo credit: darkday. / Foter / CC BY



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