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6 Reasons For Basement Flies (Easy Solutions)

Unfortunately, if you have flies in your basement, you are dealing with non-hygienic environments that attract these rather nasty insects. Since they carry diseases and promote the transfer of bacteria between surfaces, you need to get rid of them. This means finding the causes.

1. Stagnant Pools of Water

Standing water creates the opportunity for organic matter to accumulate, which creates an attractive breeding ground for flies to feed and reproduce.

When the water is in your basement, it attracts flies, which start to reproduce there. Water can accumulate in your basement as a result of pipe or water heater leaks or breakage.

Heavy rains can also cause water to seep through non-waterproofed walls and floors in the basement as well as through any windows that do not seal properly.

The water can also stagnate on the ground against the side of the house. The flies breeding here can get into the basement through windows, cellar doors, and imperfections in the foundation and walls.

Stagnant water can gather around your home’s foundations for a variety of reasons.

If your house has been built on a slope, then it is possible for water to drain down towards your basement. Often, on a slope, this will be a walkout or daylight basement.

Your downspouts can also collect water at their exit points, which can build up against the side of the house quickly as well.

Stagnant water can also accumulate after a period of heavy rainfall, after you have watered your garden, or even after washing your car.

Pool of water on the kitchen floor


Your first step is to identify the stagnant water source, and then eradicate it as soon as possible.

If you have standing water in your basement, you should consider a sump pump or more permanent solutions, like waterproofing the basement walls and floor.

It is important to empty out any buckets used for cleaning or gardening immediately, and turn them open side down so that any rain water can not accumulate in them and attract flies.

Avoid overwatering your garden so that pools of water don’t accumulate. Use a watering can rather than a hose as less water will be expelled.

You need to make sure that any downspouts are directed as far away from your home as possible so that water is not all drawn towards one spot near the foundation.

2. The Presence of Trash

If you keep your trash in the basement before you take it out to the curb to be collected, you may be attracting flies and other unwanted critters into your basement.

Any decaying food in the trash will attract these creatures and create a fruitful breeding ground for them. Once their offspring hatch, the larvae grow by eating the same rotting food in the trash, and the problem multiplies like a run-away train.

Left over food in the open trash bin with flies inside

Even just leaving it there overnight can cause an issue.

One female fly can lay over 100 eggs at a time and these can hatch in under 24 hours—sometimes they can hatch in less than 10 hours. Within 12 days, all the female flies will be ready to breed.


There is a really simple fix to this problem. Either keep your trash outside and not in your basement or make sure your trash bag is in a trash bin that has a lid that can be tightly sealed. This will prevent any flies from entering the trash bag and reproducing.

If you have had a fly infestation, then once you have removed the trash from your trash can, it is advised to give it a thorough clean on the inside and exterior.

You can use any kind of cleaning detergent, but you can also use a solution of vinegar and warm water if you prefer to limit the use of detergents. Make sure the trash can is completely dry before using it again.

Since flies are attracted to your rotting leftovers, try to dispose of them either in your garbage disposable or in a separate plastic bag that you can easily seal and dispose of in an outside bin.

3. Animal Feces

Flies are attracted to anything rotting or decaying, so your golden retriever’s daily droppings festering in the summer heat make a perfect haven for them to set up camp and reproduce.

Alternatively, your dog might decide the best place to do his business is right outside the basement window, which creates a perfect opportunity for the flies to swoop right in. This is a particular issue if your windows are left open to create a draft through the house for ventilation.

Blonde woman kneeling in the floor to pick-up a dog's poop using a plastic

Sometimes accident’s also happen inside the house, when you are not aware of it. These hidden droppings create a breeding ground for flies, which can spread around your home quickly.

Keeping your kitten’s litter box in the basement might have sounded like a great way to keep it out of sight, but the feces will attract flies into the space immediately.


There is no easier solution than to simply keep your yard clean. Try not to let the feces accumulate too much so that it will take you less time to pick it all up and it will not be standing for long enough for flies to reproduce.

Cleaning up and replacing the kitty litter is vital if you want to avoid continuous infestations of flies in your home.

If you assign just a few minutes every day to clean up after your pet, it is a simple way of preventing the problem from arising.

4. Undiscovered Animal Carcasses

Flies are attracted to rotting organic matter, and this includes animal carcasses, which can, unfortunately, hide in the dark nooks and crannies that are so common in basements.

A hole in the outside wall, floor, or the drains, might have invited unwanted rodents or other small animals into your basement. If these entrances are not viable exits as well and a lack of sufficient food, this animal could have become trapped and died behind your drywall or even in your pipes.

Undiscovered animal carcasses will be accompanied by a distinctive and terrible smell, so it will be pretty obvious if this is the source of flies.

Flies are attracted to decaying matter as they feed off of it. Once the flies find this unwanted carcass, they are able to breed quickly and can quickly become a health risk for your family.


Even though it’s an unpleasant thought, you will need to do some sniffing to find the carcass or, at least, the general area that it is in. Alternatively, follow the flies. If they are there for the carcass, they will be concentrated in that area.

Then you should bring in some good lighting and have a thorough look around in that area. Look at spaces that might, at first, seem too small. Animals can squeeze into unlikely places. Look in open pipes and drains, in cracks or gaps in the floor or wall, under and behind stored items and appliances, etc.

Removing the carcass and cleaning the area with disinfectant should solve the problem unless the flies find another food source in or near the basement (try checking all the other possible reasons for flies listed in this article if this is the case).

The next step will be to try and prevent it from happening again. Is there an old chimney down which rodents and birds enter the basement? What about broken or poorly sealed windows? What about holes in the wall or ceiling? What about the vents?

5. Dirty Drains

Some basements have floor drains to prevent water buildup. Basements used as laundries will also have drains. These drains can get dirty with organic matter on which flies can feed.

Dirty floor drain

Dirty drains attracting flies will contain the type of dirt that has an odor. In addition, you will likely see the flies going to and from the drain, so you can readily identify it as the source of these pesky insects in the basement.


Simply put, in order to prevent flies from coming to your dirty drains, you need to make sure your drains are kept clean.

A great home remedy is to combine vinegar and baking soda to make a solution. Pour this down your drain, and the foaming solution will remove any built-up dirt that might be clogging your drain. Use a piping brush to scrub down the drain even further.

Another great easy-to-do tip is to pour boiling water down the drain a few times a week.

If the flies really aren’t leaving, then do yourself a favor and get some Drano Max Gel Drain Clog Remover and Cleaner for Shower or Sink Drains (amazon link) as it can instantly unclog your drain.

The experts recommend that you stay away from pouring pesticides down the drain as the water goes back to the main source (perhaps a dam or river), which can harm any living things that might be living there.

6. Stored Food.

As we all know, a basement is a great place to store all the things that you don’t want to be visible or have space for on the main floors. However, if you need to keep any spare food in your basement, you could be at risk of attracting flies into that area.

The seal of the containers might become compromised for a number of reasons, which can create the opportunity for flies to feed and reproduce.

Your kids might have taken a cookie out of the container and not closed it properly afterward, or your containers might just be getting old and not sealing as efficiently as before.

Sandwiched packed in a plastic with flies inside

People also convert their basements, or at least part of their basements, into root cellars and store fresh produce. The environment is typically well-controlled, but all you need is one potato going bad at the bottom of the crate and it can become a fly-attracting problem.


Unfortunately, if you see your food has been infested with flies, you need to dispose of it immediately since these creatures can carry a handful of harmful diseases and they can lay their eggs in the food as well.

It is really important to store any food in airtight containers to avoid any possible infestations. The Airtight Food Storage Container Set CINEYO (amazon link) is a super affordable option that can keep a variety of food fresh and safe from pests.

In order to avoid having this extra food available for flies to devour, try only buying your food in smaller quantities so that it won’t be laying around for too long. In root cellars, have a system of checking for bad items and keep a close watch on the ventilation.

Make sure that any boxes or containers have not left behind any crumbs on the shelves as these too can attract flies.


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