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 Guide to Keeping out Bats, Birds, Mice, Rats, Squirrels, Raccoons from your Building
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InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.
Animal entry points in buildings: this article discusses how to find where animals are getting into your building and how to keep them out, including bats, birds, rats, mice, and squirrels and even raccoons. This article series focuses on removing pet or other animal odors from buildings due to pet urine, pet feces, wild animal urine, or even human urine on and around buildings or on clothing and other soft materials. The little stuffed animals in this photo include a skunk - both were innocent of any pet-crimes, but they had been placed at either side of a basement door jamb to cover stains from basement water entry.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
Suggestions for Finding the Source of Animal Entry Points in buildings
 Readers should also see ANIMAL ODORS IN buildings. A complete guide to tracking down and curing odors in buildings is at ODORS & SMELLS DIAGNOSIS & CURE. Readers should also see Black stains from animals for a description of the cause and cure of various types of stains caused by pets or other animals in buildings, and also see CAT DANDER in buildings for a discussion of animal allergens indoors and how they are detected and removed. Also see Car Odors - Animals.
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Look outside too for Bats, Birds, Rodent Entry Points - if your building has been invaded by bats, rats, mice, squirrels, or other wild animals, you should inspect both indoors and outside for openings or stains and marks that indicate points of entry and exit for those creatures.
Watch out: before sealing up a hole in a soffit or wall where squirrels or bats are entering your building, make sure the animals are not going to be trapped inside where they will be mad, frightened, hostile, even dangerous (like a rabid raccoon), or ultimately dead and another source of stink.
Consult with a pest control professional who may have a practiced eye at spotting where animals are getting into your attic, roof, walls, basement, and who may be able to provide a repellant that will at least temporarily drive them out - alive. While there are no bat control poisons currently approved in the U.S., we have found that moth balls (naphtha) are an effective repellent for bats and squirrels, though naphtha odors are also repellent to some humans.
Watch out: also for wild animal bites, bacterial and viral hazards when entering confined spaces where invaders are or have been present. The author (DF) became temporarily ill after (foolishly) working in a "clean looking" crawl space that later we realized had a heavy contamination of fecal and urine contaminated mouse dust. Bat and rodent droppings as well as bird droppings can be a source of a pathogen potentially dangerous to humans, the fungus Histoplasma capsulatum.
And a small number of bats (less than 1% of bats are rabid according to the U.S. CDC) and unfortunately in some areas of the U.S. a larger number of raccoons may be carrying rabies. If you see an animal acting oddly, stumbling, or apparently unafraid of humans and very aggressive, stay away and don't get bitten. At BUILDING SAFETY HAZARDS GUIDE we discuss handling hazards from pets or other animals that may bite a building inspector.
Bats in the Building? Our photos, below left and right (courtesy of Paul Galow), show how easy it may be to spot an outdoor point where bats were entering a building: bat droppings were noted on the ground, and stains are noted at the top of the wall just over that point. A good time to seal building openings against bats is late fall when the young have matured and leave their roosts each evening - just make sure they are not at home before you seal a building entry point. Or try installing a "one-way" flap over the opening that will let the bats out but not back in. Leave that in place for a few days or a week, then close it permanently.
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Here are two more bat-invasion photographs. You will see that the cupped metal roofing formed a nice opening for bats to enter this home, and again, a telltale collection of bat guano droppings below this very spot. Birds and squirrels also enter buildings at openings like this, as we discuss just below.
Watch out: do not kill bats unnecessarily. Bats are already in trouble in many areas of the world, including some of the 45 species found in the U.S. And we need them. Bats eat large numbers of night-flying insect pests (such as mosquitoes) and are an important part of our environment.
Watch out: Histoplasmosis (from bat
droppings) is an infection
caused by inhalation of Histoplasma capsulatum. In people with compromised
immune system this can be a particularly dangerous infection, potentially fatal if not treated. See also granuloma, iritis, lung nodules. More information is at MOLD CLASSES, LEVELS.
- Birds in the Roof Structure or attic may be entering through a hole they managed to peck in a roof overhang or soffit such as shown in our photo at below-left (courtesy of Paul Galow).
- Birds in the Attic at infestation levels may be obvious if you spot bird dropping stains such as those shown on our photo (below-right).
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Watch out: Cryptococcus infection (cryptococcosis): (from bird
droppings), at primary risk are people with compromised immune system but
normal adults can also be infected by inhalation of Cryptococcus
neoformans, leading to a form of meningial encephalitis. Cryptococcosis is a fungal disease caused by Cryptococcus neoformans or Cryptococcus gattii. Most people do not get sick with cryptococcosis, but some people are more likely than others to get this disease. For these people, cryptococcosis can cause serious symptoms of lung, brain and spinal cord disease, such as headaches, fever, cough, shortness of breath, and night sweats. Cryptococcus neoformans is found in bird droppings. More information is at MOLD CLASSES, LEVELS.
- Also check for dead animals in building attics, crawl spaces, wall or ceiling cavities and in duct work or air handlers or chimneys.
Animal odors in buildings can occur
when an animal such as a mouse or rat has died in a building cavity. A dead animal smell has been described by our clients with a wide variety of terms ranging from a vague noxious stink that seemed to vary with humidity to a sweet sickly smell.
Dead animals or even insect nests
in building plumbing, especially building vents, can also produce unexpected sewer odors - see Septic and Sewer gas odor links discussed below.
Rodents, especially in the HVAC system such as air ducts, may also be a bacterial or Hanta virus hazard.
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Are There Squirrels in the Attic?
Our photos below show a stunning nest project built by squirrels in the attic of a 1960's home in New York. The squirrels entered through openings in the home's aluminum soffit covering, tore up fiberglass insulation, and built the mounded nest in our photo at below left. Squirrel droppings on attic insulation are shown in our second photo, below-right.
Below at left we show another sign of squirrel invasion of an attic: leaves brought into the attic to add to insulation as a nesting material. One of our favorite squirrel invasion indicator photos provided by a reader is shown at below right. When squirrels nest or simply hide in an aluminum downspout, the sound or smell of the squirrel can be enough to drive some dogs mad as they try to tear their way into the squirrel's hiding place (below right).
Advice for Keeping Mice and Rats and Squirrels and Raccoons out of Your Home
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 Pest control experts recommend several simple steps that will discourage mice and squirrels from moving into your building as they are inclined to do particularly at the beginning of cold weather:
- Housekeeping: clean up spilled food, seal food in rodent-proof containers
- Garbage: garbage and trash cans should be made of metal and kept closed; clean up any spilled garbage around your trash cans both indoors and outside.
Watch out: be sure your garbage can lids fit securely - raccoons are very good at opening them up to explore.
Our photo shows a skunk rummaging on a golf course. If you see a skunk meandfering in daylight stay well away - stay away any time for that matter. This skunk was found dead two days after its photo was taken, probably due to rabies. . |
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- Pet food: we found that storing open bags of cat or dog food invited mice into the same area, a problem solved by keeping those large pet food bats in a small metal covered garbage can. We also stopped leaving pet food in bowls overnight.
- Seal Building openings: as we discussed above about bats, look outside for openings into the building such as at soffits or roof eaves, especially near overhanging or close tree branches (squirrel highways), and close to the ground look for openings into the basement at vents, windows, or building sill plates and siding bottom edges.
Seal these when you won't be trapping animals inside. We have read that mice can enter a building through openings as small as 3/8"!.
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Trim shrubs at least a foot away from the building walls; we prefer 18". This also reduces the attractiveness of the building to insect pests such as termites and carpenter ants.
If your home is in an area where Norway rats are a problem, keep low growing shrubs away from your building walls entirely as those rats burrow under them, especially Junipers and Taxus.
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Readers should also see ANIMAL ODORS IN buildings followed by Cleaning Suggestions for Odors / Urine.
If your building odor complaint source is found to be outdoors, see Removing Odors at Building Exteriors.
Also see Removing Urine Odors from Clothing This article describes bacterial/enzyme based cleaners that may be extra effective in removing human or animal urine odors from clothing, diapers, bedding, towels, etc.
To Return to Mold/IAQ Action Guide: What to do about mold, mildew, and other indoor allergens
an environmental testing guidance website explaining what to do about mold, mildew, and other indoor allergens.
Frequently Asked Questions (FAQs) about how to keep animal pests out of buildings: bats, squirrels, raccoons, skunks, snakes, birds etc.
Question: how do I clean up bat droppings & bat urine in our cabin?
We discovered a huge colony of bats living under the roof of our log cabin. I used a black-light (see UV LIGHT BLACK LIGHT USES) and found bat urine on all the main beams in the house as well as all the walls in the cabin. I have had restoration people tell me it could be cleaned and others said no all the wood is going to have to be replaced who is telling the truth? I have read that bat urine is 70% urea which would seem very strong. We believe they have been there for 6 years. - S.S. 8/12/12
Reply:
It is nonsense to replace structurally sound wood because of bat urine or other surface contaminants. What makes sense to me is to clean the area thoroughly, including HEPA vacuuming and perhaps use of a sanitizer; when the wood surfaces have dried your remediator may want to apply a sealant to give maximum odor control - it's the same process used after a post-fire remediation in a building or after a mold cleanup. More about odor control in buildings that have been peed-on or in is at ANIMAL ODORS IN buildings.
If there are wood beams or members that need to be treated and that are exposed in the occupied space, you can use a clear sealant so as to maintain the natural wood look, though the surfaces may become satin or glossy in finish.
To keep bats out of the cabin you'll want to find and screen off openings through which they have been entering. Look closely, as bats can enter a home or its attic through surprisingly small passages.
Bats are important to protect and preserve insofar as possible, though I agree we don't want them inside our homes. You might want to consult with local bat experts about installing one or a few bat houses or refuges in trees nearby.
Watch out: Histoplasmosis (from bat
droppings) is an infection
caused by inhalation of Histoplasma capsulatum. In people with compromised
immune system this can be a particularly dangerous infection, potentially fatal if not treated. See also granuloma, iritis, lung nodules. More information is at MOLD CLASSES, LEVELS.
Question: can I use peppermint oil to repel squirrels or other animals?
I have heard that peppermint repels squirrels - is that true? - Anon 9/23/12
Reply:
You might indeed want to try peppermint oil Anon, as a number of animal repellant products do indeed contain peppermint oil, such as some deer and cat repellants. There are mixtures for similar applications mix oils of peppermint, geranium, sage, lavender, eucalyptus, lemongrass etc.
But our research into common preparations whose effectiveness has been tested as a squirrel repellant shows some different suggestions. I've included details just below.
Watch out: some folks use mothballs as an animal repellent. Using mothballs for animal repellant is an illegal pesticide application and can cause other building odor or even health problems. (See MOTHBALL ODORS)
There are other specific animal repellent sprays and products sold at home and garden suppliers, often targeted to specific animals: coyote urine, for example. I've also tried pouring a bit of ammonia (or bleach but never BOTH at once) onto an area on a walkway or stair where a cat kept urinating.
List of Common & Effective Squirrel & Rodent Repellant or Rodent Aversive products
For rodents, which would include squirrels, some prepared products and specialty chemicals or preparations sold as repellents include:
- Andrographolide
- Aversives
- Bitterants
- Capsaicin oleoresin - found very effective even at low concentrations [9][10]
- Colocynth
- Denatonium Benzoate Bitterant (extremely bitter, used in a variety of products)
- Denatonium saccharide
- Natural and synthetic bitterants
- Nonivamide
- Trans-capsaicin
- Castor oil, habanero pepper
extract and white distilled vinegar have been used as a DIY spray and also are found in some patented squirrel repellant products
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Questions & answers or comments about how to keep animal pests out of buildings.
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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
- Paul Galow - technical consultant on networking, LAN design, applications support. Galow Consulting Services, 914-204-1749, email: paulgalow@galowconsulting.com
- [2] Kansas State University, department of plant pathology, extension plant pathology web page on wheat rust fungus: see http://www.oznet.ksu.edu/path-ext/factSheets/Wheat/Wheat%20Leaf%20Rust.asp
- [3] "A Brief Guide to Mold, Moisture, and Your Home",
U.S. Environmental Protection Agency US EPA - includes basic advice for building owners, occupants, and mold cleanup operations. See http://www.epa.gov/mold/moldguide.htm
- [4] US EPA - Mold Remediation in Schools and Commercial Building [Copy on file at /sickhouse/EPA_Mold_Remediation_in_Schools.pdf ] - US EPA
- [5] US EPA - Una Breva Guia a Moho - Hongo [Copy on file as /sickhouse/EPA_Moho_Guia_sp.pdf - en Espanol
- [6] "IgG Food Allergy Testing by ELISA/EIA, What do they really tell us?" Sheryl B. Miller, MT (ASCP), PhD, Clinical Laboratory Director, Bastyr University Natural Health Clinic - ELISA testing accuracy: Here is an example of Miller's critique of ELISA
http://www.betterhealthusa.com/public/282.cfm - Townsend Letter for Doctors and Patients
The critique included in that article raises compelling questions about IgG testing assays, which prompts our interest in actually screening for the presence of high levels of particles that could carry allergens - dog dander or cat dander in the case at hand.
http://www.tldp.com/issue/174/IgG%20Food%20Allergy.html contains similar criticism in another venue but interestingly by the same author, Sheryl Miller. Sheryl Miller, MT (ASCP), PhD, is an Immunologist and Associate Professor of Basic and Medical Sciences at Bastyr University in Bothell, Washington. She is also the Laboratory Director of the Bastyr Natural Health Clinic Laboratory.
- [7] Allergens: Testing for the level of exposure to animal allergens is discussed at http://www.animalhealthchannel.com/animalallergy/diagnosis.shtml (lab animal exposure study is interesting because it involves a higher exposure level in some cases
- [8] Allergens: WebMD discusses allergy tests for humans at webmd.com/allergies/allergy-tests
- [9] Christopher S. Fitzgerald, Paul D. Curtis, Milo E. Richmond, Joseph A. Dunn,"Effectiveness of Capsaicin as a Repellent to Birdseed Consumption by Gray Squirrels", National Wildlife Research Center Repellents Conference 1995, USDA National Wildlife Research Center Symposia
Abstract: We evaluated the efficacy of capsaicin as an aversive agent to captive and free-ranging gray squirrels (Sciurus carolinenssi). Capsaicin appeared more aversive in lipid-based formulations. Sunflower hearts treated with capsaicin oleoresins at 100,000 Scoville Heat Units (SHU's) demonstrated near-complete aversiveness to captive squirrels. These treatments were sampled by food-deprived captive squirrels, but were not consumed due to their extreme pungency. Additionally, capsaicin-treated suet was very effective at lower concentrations than was observed with seeds (24,000 SHU-suet versus 100,000 SHU-seed). Three ground-pepper treatments (A = 8,250 SHU's, B = 27,500 SHU's, and C = 82,500 SHU's) offered simultaneously with control seeds to free-ranging squirrels revealed a dose-dependent aversive response. These same three treatments (A, B, and C) on sunflower hearts with control hearts available were also avoided by free-ranging squirrels; however, there was no significant differences (P>0.05) in mean consumption between the capsaicin levels. Apparently, even low capsaicin concentrations (8,250 SHU's) are as aversive as higher concentrations (27,500 to 82,500 SHU's) when applied directly to sunflower hearts.
- [10] Ron J. Johnson, Ann E. Koehler, Orvin C. Burnside, Stephen R. Lowry, "Response of Thirteen-Lined Ground Squirrels to Repellants and Implications for Conservation Tillage", Wildlife Society Bulletin
Vol. 13, No. 3 (Autumn, 1985), pp. 317-324, Allen Press
- [11] Chapman, Janet Bivins, "Effectiveness of capsaicin as a squirrel repellent at bird feeders", Thesis (M.S.) - Mississippi State University. Department of Biological Sciences.. Bibliography: leaves 31-33.. Financial support from Department of Biological Sciences, Mississippi State University, and Animal Damage Control of the U.S. Department of Agriculture. --- p.iii-iv.
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