WHY ARE FOUNDATION VENTS A PROBLEM?
It is hard to believe how few homes that I see around Bristol, Johnson City, or Kingsport areas have “wildlife secure” foundations. In fact I believe that this is a national problem. Issues range from poor fit between the siding and foundation to issues with foundation vents, but problems with foundation vents are one of the most common issues. This comes either from poor installation or from shoddy construction right in the factory. In fact, my opinion, it is impossible to find a properly constructed foundation vent that will keep wildlife out of a crawlspace on the shelves (or for that matter on the website) of traditional construction or home improvement vendors. The construction industry just doesn’t know critters.
Most of these vents are made from plastic or light grade “window screen” materials. Fiberglass or light aluminum storm window type screen is used in the construction of these vents. Unfortunately, neither of these materials will prevent a rodent from gnawing through the screen. Frames are made from light metal or plastic. Screening and louvers are too light and can be easily gnawed or bent giving access.
Rodents, for example, have perpetually growing incisors. Incisors are the four most prominent teeth in the front of the mouth. (Think about the prominent front “buck teeth” used by beavers to gnaw through tree trunks to drop them to the ground.) These teeth never stop growing through the entire life of the animal. So, the animal is happy to use these teeth to modify its environment to suit its purpose and does it easily. These teeth serve as easy to use “keys” that open many doors. If the animal can get these super incisors on the edge of this light metal, they can even tear their way through.
WHY ARE ANIMALS GOING INTO MY CRAWLSPACE?
In the tri-cities region raccoons, Opossums, skunks, rats, mice are highy abundant. Abundance of these species is much higher than most residents know, and calls regarding these species in crawlspaces come in with alarming frequency. In the wild, these animals would likely use natural cover of a hollow log, culvert pipe, abandoned burrow of another animal, etc. But, a crawlspace is cozy and it doesn’t matter that the entrance is rectangular instead of round like a hollow log. These species key in on it just the same.
In fact, compared to natural denning sites, crawlspaces have several superior qualities. First, they are insulated. This keeps the animal warm just like it keeps you warm. Most species have no problem whatsoever making a nest in your insulation. Evidently their fur protects them from the itchiness of the insulation or they just don’t mind the itch. I guess that if they already have fleas a little bit of insulation itch isn’t that noticeable. Insulation also serves well for cozy nesting material.
Second, it doesn’t rain or snow in your crawlspace. It may be somewhat dank, but a leaky roof Is much less likely. And finally, it is also private. People rarely visit their crawlspace. Often calls regarding a critter found in the crawlspace involve a repairman, cable guy, home inspector, etc. Plenty of animals in the “crawlspace loving” group can make a career of birthing babies in the crawlspace.
WHY DID I NOT SEE ANYTHING GO INTO MY CRAWLSPACE?
Most species that prefer to nest or take cover in crawlspaces are nocturnal or are at least experts at avoiding predators. So, they have special “hide and escape” instincts. The nocturnal lifestyle is developed largely so that they can escape detection by predators in the wild. This lifestyle allows them to can come and go quite successfully at night while the residents are sleeping. It is too easy to miss seeing the offending critter actualy enter your crawlspace. This is why I suggest yearly inspections. If you think that you may need to have a yearly inspection check out our annual wildlife inspection page.
WHAT KIND OF ANIMALS ARE FOUND IN CRAWLSPACES?
Opossums are one of the most common crawlspace invaders. Opossums don’t dig their own burrow and so they are obliged to use a readymade nesting area. If it is nesting season they like to drag in some loose leaves and mix it with some of your insulation to form a really cozy little nest. They may crawl up a pipe or floor support piling to make the nest in the insulation between floor support joist. This puts the nest directly under your flooring. Other times they choose to make their nest one the ground if there is some type of structure or debris to make a cozy nesting spot. Opossums always leave significant quantities of poo to clue you in on what species was there if they have been there any time at all. Opossums are often heard through the HVAC ductwork because they like to climb up on the ductwork and walk around. We pulled out a momma ‘possum and eleven babies from under one building in Elizabethton this year.
Skunks are good diggers; but appreciate a readymade home in the form of your crawlspace. After all, why go to the trouble of digging a den when there are so many good crawlspaces available out there? The skunk may go ahead and do some additional work and dig a small den if the crawlspace has a dirt floor (most do). Skunks make long term visitors and are likely to stay in a den until the young are mature enough to go out on their own. Skunks don’t make a lot of racket and are likely to go undetected until somebody under there sprays. This can happen because another animal (often the owners or neighbors cat) goes under there and starts a fight. It can also happen as the juvenile skunks start to grow. Juveniles don’t have really good control of their spray.
Raccoons occasionally show up on crawlspaces too, but not as often as other species. Raccoons prefer to den in attics, so that reduces the likelihood that they will show up in denning season. They are much more likely to show up in attics. (If you are hearing attic noises or think that you have raccoon issues check out our pages on Removing Raccoons from Your Home or Everything You Need to Know about Raccoons.) However, they do appreciate the moderate temperatures and privacy of a crawlspace and are glad to use one when they are in the mood.
Domestic cats are another problem in crawlspaces. They are happy to use a crawlspace as their “relaxation zone”, “brawling area”, “escape zone”, etc. Unfortunately, they like other species, leave plenty of poo in these areas especially if they can find some nice loose dirt to cover it up with. There is nothing worse than crawling under a home to find large poo deposits. That is for sure.
Occasionally, even groundhogs need a secure place to live and your crawlspace is just that. Groundhogs can dig their own burrows. In fact they just love to dig. But if the privacy of a crawlspace is available and there is a dirt floor underneath to dig into, all is good. This can be worse than other “non digging” species. These guys can rearrange the supporting soil under foundations and pilings and cause structural issues with your home.
SKUNK SMELL IN CRAWLSPACE
Lots of times,things can go along unnoticed by the homeowner until something goes really bad down there. A skunk that is unmolested can come and go without creating a serious odor. In fact, I have seen situations where the skunk has used the crawlspace for several seasons prior to detection. can go a long time in the crawlspace unnoticed until it meets a cat or other critter and they have a disagreement. The homeowners will not have to wail till daylight to understand what has been happening under their home. The stench will tell them immediately. If this happens, we can treat the problem. Check out our page on dealing with skunk smell.
DEAD ANIMAL SMELL IN CRAWLSPACE
When I start to feel sick I usually want to go home and crawl in bed and take it easy. I think it is the same with crawlspace critters. If things go bad and they get sick or hurt they may head to the nearest quiet, secure, and private crawlspace to recuperate. Unfortunately though, they don’t always pull through and BAM the homeowner comes home one evening to notice a horrible smell in the house. The smell gets worse for a couple days and no one can stand to be in the house.
If mom is denning in the crawspace she may leave her litter down there while she goes out to feed. If something happens to her, she may not come back home. Then there is an entire litter of rotting babies down there to be found and exctracted. Blech. The persistent fly problem that comes with this can be a really good clue to what is going. There is always a prodigous supply of maggots found along with the rotting corpse.
WHAT KIND OF MESS DO CRITTERS LEAVE IN MY CRAWLSPACE
Once they are finished nesting , they leave behind compressed insulation that doesn’t do its job of retaining heat and is full of droppings, old nest materials, parasites, etc. Opossums, rats, and mice are especially fond of nesting sites in insulation.
Raccoons may enter crawlspaces, but are much more likely to nest in attics where they leave their own brand of mess and destruction. They can destroy flexible ductwork which then is left open to crawl through. This can bring animals up to the floor registers to peep through at you and possibly enter the living spaces. We had several cases like this in 2017.
Poo deposits are almost always present if animals are coming and going through the crawlspace. Deposits can be heavy if the problem has been present for a long time. These deposits always have the possibility of carrying parasites and diseases. This makes crawling through these areas especially unpleasant. Our Extreme Rat Inspection video shows what you can end up with in a crawlspace and why you should keep your foundations secure.
HOW DO THE CRITTERS GET INTO MY CRAWLSPACE?
Often this is easy to see. Vents are often loose, fallen off, poorly fited, or completely missing. Vents with small gaps are excellent entrance points for mice or rats. Vents with larger openings are very attractive to skunks, raccoons, opossums, and cats. If vents are loose, they may be torn off, if the animals are motivated. Sometimes the masonry around the vent is at fault. Mortar and brick in older homes is sometimes soft and makes for a poor substrate to anchor into.
If foundation vents are in place, but have been cut through, the most common culprits are mice followed by rats. The entrance hole needed by each is different in size and this can help diagnose which species is the problem if this isn’t already known. Gray Squirrels, flying squirrels, and species that have arboreal habits have the capability to cut through a foundation vent, but that prefer to enter homes in much higher locations. Foundation vents are rarely cut through by squirrels.
The rats and mice that you are dealing with inside your home all have the same set of perpetually growing front teeth that they use to cut through whatever gets in their way. Rodents are often the downfall of this type of vent.
HOW TO GET THE ANIMAL OUT OF THE CRAWLSPACE
Let me just tell you. This one can be trickier than you might think. The critter has the upper hand in such a situation. Crawling into a crawlspace with a wild animal is not recommended. They can stand up and run down there while a person can only crawl or wiggle along on the belly. If you corner the animal down there and it comes down to “hand to hand combat” you will probably loose. If you happen to meet a skunk down there you may become a society cast out for some time. Skunks are good shots and if they hit you in the face it can blind you. Furthermore, you may have seen an opossum go in, but you cant watch the foundation all the time. You have no idea what all is down there. Don’t go in unless you know what you are doing. It is not worth it. Don’t try it!
Instead of “hand wrangling” the critters out, we use specially made one way doors and shielded heavy duty double door box traps. These devices are specially designed for just this situation. These devices are mounted directly over the entrance so that the animal must pass through to go out and feed. They are mounted directly to the building and staked in place to prevent the animals from reentering. These traps will catch the animal if it happens to be on the outside and tries to reenter or if It tries to exit the crawlspace.
HOW TO KEEP ANIMALS OUT OF THE CRAWLSPACE
When we encounter customers with this type of problem it is difficult to solve the problem with materials that can be purchased from conventional building suppliers like Lowes or Home depot
Installing a retrofit cover plate to keep wildlife out of the crawlspace.
The one and only tried and true way of keeping your crawlspace clear of unwanted critters permanently is to seal up the vents like Fort Knox. We recommend using premade expanded metal mesh grates. The mesh in these grates is made from an actual metal plate that is slotted then stretched to create a strong mesh. It is strong enough to stop any rodent from cutting through. They are stainless steel and come in three colors black, white, and gray. (See photo below). Our foundation plates are premade to fit over standard vent openings. They do not require removing the original vents which can be left in place to control ventilation.
Installation of these vent covers requires special tools. They should be installed by screwing them directly to the brick with masonry screws. To do this a hammer drill will be necessary. The difficulty of installing these vent covers will vary depending on the age and quality of the brick. Older brick may be very soft and crumbly and may not hold up well. Some new brick will be extremely hard and will need special bits to drill. In either case, it may be easier to contract a professional to help negotiate this problem.
If you want to see how this is done.This video shows you how we retrofit foundation vents to keep wildlife out Whether you are talking about permanent poo deposits, chewed up wiring, damaged ductwork, catfights, or having an unfortunate meeting with a wild animal the best advice is to seal up the foundations to keep all these critters out.
