calcified bat urine in attic of home

We talk a lot about bat guano and how it can negatively impact our lives but what about bat urine? It’s something that doesn’t get as much attention so do we even need to discuss it? Well, you might be surprised that it’s not a subject to be overlooked. Why not?

Let’s start with the fact that bat urine contains high concentrations of uric acid which is strong enough to corrode metal. If left, over time it can begin to affect a building’s structure, such as the waterproof membrane beneath tiles or metal sheets of a roof, leading to structural damage.

Over a long period of time urine may also cause mild wood damage. When the urine saturates the surfaces of dry wood beams the wood fibers expand and separate. These fibers then are torn loose by bats crawling over the surface.

It’s not only your home that is in danger from bat urine. Leptospirosis is a bacterial disease that, in rare cases, can be fatal to humans. Rodents and cattle are the main carriers, but bats may also be infected. To prevent infection, it’s important to avoid bat urine from coming into contact with broken skin, your eyes, nose, or mouth.

bat colony above an exterior wall stained their urine

How Do I Identify Bat Urine?

If you do have bats, you may notice their urine leaking down an external wall from an entry or roosting point. Bats often like to roost in tight spaces, for example between window frames or tiles, in structural voids, the spaces between the exterior and interior parts of a building, in attics, and between walls. What does it look like? Bat urine normally leaves a barely visible residue which looks like a milky exclamation mark with a long downwards streak. 

Does it smell? Bat urine has an ammonia-type smell and the larger the colony the worse the smell becomes. Urine from a single bat is relatively odorless but if you have a moderate-sized colony the smell will be more obvious, and the odor will increase during damp weather. Bear in mind that although you may not have an odor in your home right now, it doesn’t mean that bats aren’t there. It may just mean that it hasn’t had time to build up enough to start to smell.

bat urine staining on the interior wall of a house

What Should I do If There Is Bat Urine On My Property?

If you do have an odor, a musty, ammonia type smell in your home, and no explanation for it, you could indeed have a large bat colony in residence. If you haven’t noticed a smell perhaps you have noticed bat guano? This could also be a sign that you have a colony in your home and ignoring the fact that bats have moved into your house is not a wise decision; having bats in your home is not healthy or safe for you or your family. 

What if you have a bat problem in your commercial property, hospital, or school? Consider the far-reaching implications for your staff, customers, students, and patients. So if you need residential or commercial bat removal what should you do? 

Firstly, we recommend a twilight watch to see if bats come flying out of your house. That’s the best (and totally free) way to know for sure if you have an infestation. If you have a large home or commercial property this may not be possible due to the size of the property, if this is the case call us directly to talk over other options.

a bat free house

Once you’ve done this and confirmed you do have a bat problem, call the professionals to inspect your property and get you a proposal to handle the problem once and for all. If you are on a tight budget, take a look at our DIY guide to bat removal.

Bat infestations are dealt with most efficiently and effectively by an experienced bat removal specialist. If you think you’re dealing with an infestation in your home or business, contact our customer service team at (877) 264-2287. They can answer all of your questions. 


Michael Koski

Get Bats Out Owner and President Michael Koski

Your Local Bat Removal Specialist

Print Friendly, PDF & Email

Comments 8

Leave a Reply

Your email address will not be published. Required fields are marked *

  • Kate

    May 29, 2024 | Reply

    Please help!! The smell has gotten worse over the last few months but I'm also concerned if it's mice 🤢I don't know where you're located or if you can help me find someone in Eastern Washington 🤔. Thank you!!

    • Tori Bruce

      June 4, 2024 | Reply

      Sorry the scent is getting worse. Please feel free to call our customer service department to see if we are available where you live. 877-264-2287

  • Tim

    April 7, 2024 | Reply

    Need a recommendation for an enzyme cleaner to remove bat urine smell. Had bats in a farm attic for years. They have been gone for 20yrs. Rehabbing house Need to remove smell from rafters. Thanks Tim

    • Tori Bruce

      April 9, 2024 | Reply

      Hello, our technicians have had success with the following formula: 1 part boiled lindseed and 5 parts Naphta. Amazing how potent bat urine can be even after 20 years!

  • I did have the bats and got rid if them, but now I have the horrible smell, what can I do?

    July 18, 2023 | Reply

    I had the bats, they were removed. But now I have the smell. My ceiling are very high. I am afraid the solution might be very expensive. Any suggestions would be appreciative. Sincerely, Cielo.

    • Tori Bruce

      July 24, 2023 | Reply

      Hi, I'm so sorry you are having to live with the smell. It is possible your insurance may cover the bat cleanup though. Our customer service agents can give you more information about how to approach insurance. 877-264-2287 and we offer cleanup services (specializing in bat guano and damage).

  • Pat Dawson

    May 9, 2021 | Reply

    Having a new found a bat roosting.......popped it in a box but it escaped......contacted the Bat Society........who looked everywhere for the bat and suggested we get a bat box. The bat box is pretty heavy and large and after reading various comments on the websites......feel that I do not want to encourage them for various reasons.

    • Tori Bruce

      May 10, 2021 | Reply

      Bat boxes are a nice idea but kind of a gamble on if they'll work the way you want them to or not. Definitely installing it away from your home is a good idea. Bats are quite messy when they come and go! Also, there is no guarantee that the bats will want to lodge there. Thank you for thinking of helping the bats, we need as many of them to thrive and be healthy as possible! You can also check out this article: for more ideas.

  • Leave a Comment