Guide to Keeping out Bats, Birds, Mice, Rats, Squirrels, Raccoons from your Building
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How to keep bats, birds, rats, mice, and squirrels out of your building
Sources of indoor building smells and odors from dogs, cats, rodents, bats, unusual pets, and even people can be tricky; here are our suggestions.
Signs of bats, birds, squirrels in the attic
How to get rid of mice and other rodents in buildings

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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.

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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Suggestions for Finding the Source of Animal Entry Points in buildings

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.

Stains from bats on a building wall (C) Daniel Friedman

Droppings indicate bat activity at a building (C) Daniel Friedman

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.

Entry point for bats at a building (C) Daniel Friedman

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).

Bird entry point into a roof overhang(C) Daniel Friedman

Bird dropping stains on an attic beam (C) Daniel Friedman

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.

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

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.

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 sillplates 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"!.

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.

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.

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MVOCs & MOLDY MUSTY ODORS
MYCOPHOBIA, STAINS MISTAKEN for MOLD
MYCOTOXIN EFFECTS of MOLD EXPOSURE

Nanomaterials Hazards
NOISE / SOUND DIAGNOSIS & CURE

ODORS & SMELLS DIAGNOSIS & CURE
ODOR DIAGNOSIS CHECKLIST
ANIMAL ODORS IN buildings
  Finding the Source of Animal Odors
  Cleaning Suggestions for Odors / Urine
  Removing Odors at Building Exteriors
  Removing Urine Odors from Clothing

BUILDING SAFETY HAZARDS GUIDE
BUILDING SETTLEMENT

CAR MOLD CONTAMINATION
CARBON MONOXIDE - CO
CARPETS & PADDING ODORS IN buildings
CHINESE DRYWALL HAZARDS
GAS DETECTION & MEASUREMENT

HEATING OIL EXPOSURE HAZARDS, LIMITS
HEATING SYSTEM ODORS
HOUSEWRAP AIR & VAPOR BARRIERS
MOLD ODORS, Musty Smells in buildings
MOLD ODORS in Cars
ODOR DIAGNOSIS CHECKLIST
ODORLESS CHEMICALS / GASES: CHECK FOR?
ODORS, PLUMBING SYSTEM
ODORS, SEPTIC or SEWER
ODORS, SULPHUR SMELL SOURCES
ODORS, URINE REMOVAL
ODORS GASES SMELLS, DIAGNOSIS & CURE
ODORS IN WATER
OIL HEAT ODORS
OIL TANK LEAK ODORS
OZONE for MOLD OR ODORS
PAINTS & COATINGS ODORS IN buildings
PLASTIC CONTAINERS, TANKS, TYPES
PLASTIC HEATER VENT
PLASTIC ODORS-SCREENS, SIDING
PLUMBING SYSTEM ODORS
SEPTIC SYSTEM ODORS
SEWER GAS ODORS
SEWER GAS ODORS in COLD WEATHER
VINYL Siding or PLASTIC Window ODORS in buildings
VINYL CHLORIDE HEALTH INFO
WATER ODORS

Paul Galow - technical consultant on networking, LAN design, applications support. Galow Consulting Services, 914-204-1749, email: paulgalow@galowconsulting.com

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
Environmental Health & Investigation Bibliography - our technical library on indoor air quality inspection, testing, laboratory procedures, forensic microscopy, etc.
Adkins and Adkins Dictionary of Roman Religion discusses Robigus, the Roman god of crop protection and the legendary progenitor of wheat rust fungus.
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
"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
US EPA - Mold Remediation in Schools and Commercial Building [Copy on file at /sickhouse/EPA_Mold_Remediation_in_Schools.pdf ] - US EPA
US EPA - Una Breva Guia a Moho - Hongo [Copy on file as /sickhouse/EPA_Moho_Guia_sp.pdf - en Espanol

Allergies, Allergens, Allergy Testing in buildings - References & Products

Air Conditioning System Blower Fans & Filters Cascading for Optimum Indoor Air Quality
Allergen Tests in buildings advice about how to test, what to look for, in evaluating the level of dog, cat, or other animal allergens in a building
"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.
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
Allergens: WebMD discusses allergy tests for humans at webmd.com/allergies/allergy-tests
Animal Allergens: Dog, Cat, and Other Animal Dander - Cleanup & Prevention Information for Asthmatics and regarding Indoor Air Quality.
Atlas of Mold Related Illness Symptoms & Complaints - long list of both documented, studied mold related illness, and complaints ascribed to mold contamination or allergens in buildings
Cat Dander: how to inspect and test a building for past or current presence of cats, cat hair, cat dander, and cat allergens
Clinical Atlas of Mold Toxicity - An Online Description of Toxic, Pathogenic, Allergenic Fungi, Fungal Diseases
Fiberglass Insulation Contains Mold© 2005 comments about a field study in process, & more about health hazards from fiberglass insulation
Humidity: What indoor humidity should we maintain in order to avoid a mold problem?
Mold Action Guide detailed guide on finding, removing, and preventing indoor mold contamination
Odors, Odor Detection, Smells, & Gases how to find and identify sources of noxious or toxic odors and gases
Other environmental risks, Our much longer list: Asbestos, carbon monoxide, electromagnetic fields, etc.
Ozone: The Use of Ozone Indoors for Control of Odors and Mold Removal in buildings: A Summary of Hazards and False Claims.
Pollen Allergens: identification, plant pollen and indoor air quality
Products to Reduce Mold & Allergy Problems to reduce indoor mold or allergen levels: air cleaners, air purifiers, dust mite covers, vacuum cleaners, crawl space vents
Recognizing Allergens: What various indoor allergens look like - identification photos to help identify pollen, dust mites, animal dander, toxic or allergenic mold - Common Mold and other Allergens, Irritants, Remedies & Advice
Rodent control issues, including dander, fecal, and urine contamination of buildings and Building insulation are discussed at our
Sewage and Septic backup contamination in buildings: inspection, testing, remediation, & references to expert sources
Action Guide: What to do about mold, mildew, and other indoor allergens
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Suggestions for Finding the Source of Animal Entry Points in buildings

Are There Squirrels in the Attic?

Advice for Keeping Mice and Rats and Squirrels and Raccoons out of Your Home

Questions & Answers regarding this article

Ask a Question or Search InspectAPedia

Technical Reviewers & References

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

Allergies, Allergens, Allergy Testing in buildings - References & Products