Rats are one of the most successful commensal species in history, adapting to our human environments with terrific speed and skill. Our infrastructure, buildings, and supplies have given them everything they need to flourish, so if you’ve detected a subtle scurrying sound coming from your roof, there’s a good chance your home has become theirs.
So—how do you get rid of roof rats? And how do you know if you have them in the first place? In this article, we’ll cover everything you need to know about rats in your roof, so that you can keep your home pest-free.
What types of rats are found in roofs?
A black rat—the most common type of roof rat.
The two types of rats you’re likely to find in a roof are black rats, or brown (Norway) rats, with the former being much more common. Black rats have light brown to black fur, and are between 12.75 to 18.25 cm long, including a 15 to 22 cm tail. That means the mightiest black rat in your roof might be the length of a bowling ball, though nowhere near as round.
Rats are warm-blooded creatures like us, so they need shelter and warmth to survive. That’s why a roof can make a perfect home, which can easily be reached with their excellent climbing skills. Other common household homes for rats include garages, sheds, basements, cabinets, and inside walls.
Black rats originated in the Indian subcontinent. They quickly spread with the invention of trading ships, and can now be found everywhere in the world. They are famously prolific breeders, whose females become sexually mature after two to five months. Then they can have up to 40 babies a year. According to Rentokil, in an ideal environment, two rats can turn into 1,248 in just a year1. In three years, you could have 482 billion rats—your own personal rodent army!
Why roof rats are a problem
Rats are pretty cute, but the last thing you want is a hoard of them living in your roof. These are the two biggest reasons why:
Disease
Most people know about the Black Death bubonic plague in the 14th century—a pandemic that killed between 75 to 200 million people in Eurasia and North Africa2. Rats were thought to be instrumental in its spread, because the fleas they carried in their fur were infected with the bacterium that caused the disease.
Bubonic plague is less of a problem these days. But modern rats can carry and spread a parade of other diseases, like hantavirus, salmonella, ringworm, and leptospirosis. It’s believed that rats carry more human diseases than any other life form, transmitted to us through their faeces, urine, or saliva, which they can leave plenty of around your home.
Rats can also carry ticks, lice, and fleas, which have their own diseases that can be easily passed onto humans.
House damage
A rat’s jaw can exert a force of up to 24,000 pounds per square inch. By comparison, an American pit bull’s bite is 235 pounds per square inch. That means a rat’s bite is over 100 times stronger than a pit bull’s, which is why they can chew through brick, concrete, sheetrock, and pretty much anything else in your home.
Rat’s teeth constantly grow, so they have to gnaw on things to keep them at an appropriate size. They also chew as a way to gain entry to places, to build nests, and to find food. When they’re living in someone’s roof, the result may be broken drywall, beams, water pipes, and electrical wire, which are not only expensive to fix, but can also lead to hazardous safety issues. If your electricity suddenly goes kaput, and you’ve detected other signs of rodents in your home, you may discover a fried rat somewhere.
How to identify rats in the roof
Thankfully, there are plenty of telltale signs of rats living in your roof.
A dead rat
Found an upturned black rat in your home? It may have come from your roof, and because they love getting jiggy, there’s probably more. If you can safely access your roof cavity, check for faeces, bite marks, nests, and of course, other rats.
Noises
When roof rats scurry around and gnaw on things, you may be able to hear scratching or grinding sounds, or even the occasional thud. You won’t hear squeaking because they use high-frequency ultrasonic vocalisations that we can’t hear. But dogs and cats can easily detect rat chatter, so if you’re noticing them becoming animated for no reason, or fixated on the ceiling, they may have found rodents. Or they’re being their weird selves as usual.
Suspicious roof noises can be caused by possums too. Check out our article on how to detect and remove possums from your roof.
Faeces
Rat faeces on a glue trap
Rats can produce up to 40 droppings a night, and they’re usually concentrated in single areas. You might find them behind storage shelves, boxes, underneath appliances, and in the roof itself.
Rat faeces are brown or black, and between 10 to 18mm long with pointed ends. It can look similar to a grain of rice, but darker and larger.
Gnaw marks
Rat marks on a bar of soap. This rat had excellent breath for a while
Rats chew on pretty much everything, so look out for damage in your walls, supporting beams, pipes, and wiring. Anything that looks like it’s had chunks taken out of it.
Dirt marks
Rats don’t have daily showers or baths like we do. This causes dirt and grease to build up in their fur, which can easily rub off on walls and flooring, and alert you to their presence. Look out for dark stains like those seen in the picture above.
Nests
Rat’s nest on a cardboard box.
Rats keep away from humans and other predators who want to kill them, so nests can be tough to find. They’re usually in hard-to-reach places like cavity walls, crevices, and under eaves, and are made of debris, twigs, cotton, plant materials, and anything they can get their paws on.
Half-eaten fruit or vegetables
If you have a fruit tree in your garden, or your own little vegetable patch, any produce you leave lying around can be hollowed out or partially eaten by rats. Of course, this doesn’t mean you have rats in your roof, but if you’ve recognised other signs like rat poo, it’s worth taking a look.
How to get rid of roof rats
So how do you get rid of roof rats? If you’ve confidently identified vermin in your roof cavity, these are the most effective ways to get rid of them.
Traps
Traps are one of the most effective ways to get rid of roof rats, but they vary in quality depending on their type. We’ve ordered our recommended trap types by effectiveness and humaneness.
Traps also need bait to lure the rat—these are the best baits you can use:
- Peanut butter
- Smelly cheese
- Hot dog
- Chocolate
- Cat or dog food
When you’re setting up traps, keep an eye out for rats in the area. They can bite and even chase you when threatened.
Snap trap
Snap trap. Image from Catchmaster Pro
Snap traps are the traditional rodent-catching traps with the steel bars that snap down onto the animal’s neck. They may seem inhumane, but a well-designed snap trap will quickly kill the rat without causing any pain, so they are considered one of the best ways to get rid of roof rats.
Snap traps need to be checked daily for captured rats, just in case the device has come down onto the wrong part of the animal’s body. If this happens and the animal is in pain, hard as it can be, you’ll need to kill the rat with a quick, heavy blow to the head.
When setting up the trap, the RSPCA recommends the following:
- Place the bait in the marked area, and keep the rest of the trap clear of food. This ensures that the steel bar comes down on the rat’s neck.
- Place the traps parallel to the wall, which follows the rat’s natural course, and encourages it to walk onto the trap correctly.
Live trap
A live rodent trap. Image from eBay
Live traps use spring-activated doors and bait to trap animals, without killing them. Once trapped, the rat should be released in the countryside.
These types of traps may appear to be the most humane way to get rid of roof rats, but unfortunately, relocated rats have an extremely low survival rate3. The traps also need to be checked daily, with food, water, and nesting material provided. Otherwise they become one of the most inhumane trap types, because the poor rat can die of thirst or hunger.
A poorly designed live trap can also catch the rat’s tail, causing pain until you’re able to release it.
Electronic trap
Electronic rat trap. Image from Amazon
Electronic traps work by luring the rat into a plastic chamber, and then delivering a high-voltage electric shock to kill it. Customer reviews are mixed for this type of product—some say it’s effective, and others not. It’s difficult to confirm whether this type of trap is humane or not. Be sure to do plenty of research on a product you’re considering.
Glue trap
We’ve included glue traps in our list, but they are an incredibly cruel and inhumane way to trap rats, so please don’t use them.
Glue traps are usually flat pieces of cardboard coated in strong glue. This traps the rat on the surface, and in its desperation to get free, it will rip its fur, tear its limbs, and even chew off its own legs.
Poisons
Poisons are an appealing way to get rid of roof rats. There’s a good chance the rat will remain hidden while dying, so you won’t have to see or deal with it. Sadly, as with glue traps, poisons are a horrible and inhumane way to deal with rats. They contain anticoagulants which thin the rat’s blood and cause internal bleeding, which can suffocate them, swell their bodies, give them seizures, and a whole lot more nastiness.
There’s also a risk of other animals consuming the poisons. A study in 2018 found that over 70% of dead boobook owls had high levels of rat poison in their blood, indicating that the poison probably killed them4.
Please don’t use poisons.
Remove food and water sources
Once you’ve humanely eliminated or removed rats from your property, you’ll want to ensure the buggers don’t return. Rats will only set up shop in places where they have access to food and water, so by removing these two things from the environment, they will move onto another spot.
Like us, black rats are omnivores, so will eat whatever they can get their paws. These are the food sources you should remove from around your home:
- Pet food. Many people keep their pet food in an outer area of the home, like a laundry or shed. This is easy pickings for a resourceful rat, so keep your pet food in a tight metal container.
- Food or crumbs. It’s easy to make yourself a sandwich and forget to wipe the crumbs off the sideboard. The rats in your roof will look down with adoration. Keep sides thoroughly wiped at all times.
- Home-grown vegetables. Vegetable patches are a cheap, healthy, and delicious source of free food—for both you and your roof rats. To deter rats, you’ll need to keep your compost bin clean and well-sealed, block off their paths of entry (look for grease marks), and remove any sources of water (more on this below). If you grow chillies, beware of fire-breathing rats.
- Fruit trees. Mangos, apples, peaches…rats love them all. Be sure to pick up dropped fruit from your lawn.
These are the water sources you should remove from around your home:
- Leaky hoses or taps. One of the most common sources of water for rats. Get this fixed!
- Pet water bowls. If you keep your pet’s water bowls outside, bring them into the kitchen instead.
- Air conditioning condensate drain. Your AC’s condensate drain is where moisture is expelled from the system. It’s a PVC pipe that sits next to your outdoor unit. This can be a tricky one to fix, but using a small plastic container to collect the moisture might do the trick. Or even a plastic bottle cut in half. You’ll just need to regularly empty the container.
- Potted plant saucers. Remove saucers from underneath plants, as they are a great source of water for rats.
- Sprinkler lines. If you have an irrigation system, check the outlets to ensure that nothing is leaking.
- Birdbaths. Temporarily remove your birdbath until you fix your rat problem.
Remove rubbish and clutter
Rubbish can be both a source of food and a hiding place for a rat, so be vigilant with your rubbish and always keep it in a tightly sealed bin (wheelie bins work). Other clutter like paper, wood, and cardboard boxes should also be removed if possible. The more rubbish you leave lying around, the happier your roof rats will be.
Call an exterminator
If all else fails, and your roof remains a safe and cosy home for rats, calling a professional should do the trick. They’ll use their knowledge and experience to quickly solve your rat problem, but at a cost. You can expect to around $342 on average, although this number varies depending on where you live, and the size of your infestation5.
What not to do
These are some common solutions that people recommend, none of which have proved to work effectively:
- Mothballs—mothballs contain a chemical called naphthalene which deters rats. However, mothballs don’t contain enough of the chemical to be effective.
- Strong scents—some people suggest using items with strong scents to deter rats, like ammonia, peppermint oil, or chilli flakes. Unfortunately, there’s no evidence to suggest that these products work. The rats probably just get used to the smell.
- Cats—cats are great at catching mice, but not so good at catching rats.
- Sound devices—you can buy products that emit high-frequency sounds that rats dislike. However, they aren’t proven to have a lasting effect—as with strong smells, the rats get used to them.
How to stop rats getting in the roof
We’ve covered how to identify rats, how to eliminate them, and how to keep them away. The final piece of the puzzle is how to block them from getting into your roof in the first place.
Rats usually access your roof through holes and cracks, drains, doors and windows, and pipes, and there’s plenty you can do to prevent this from happening. These are the best methods:
- Find holes and cracks that are 20mm or bigger, and seal them up with caulk. You can also use steel wool if you need to. In the roof, you can usually find holes in rafters, gables, and eaves.
- Place metal screens/cages over vents and chimneys.
- Block gaps under sinks and appliances.
- Cut back trees and shrubs, particularly any that are overhanging the roof. These are great entry points for acrobatic rats.
Summary
Rats are tenacious little buggers. With reliable sources of food and water, and easy access points, they will easily make your roof their home, and can multiply to astonishing numbers. If you detect rats in your roof, it’s crucial to fix the problem as quickly as possible, and we hope that this article has given you everything you need to do so.
Good luck!
References
- Rise of the rats | Rentokil, Rentokil
- Black Death – Wikipedia, Wikipedia
- What is the most humane way to kill pest rats and mice? – RSPCA Knowledgebase, RSPCA
- Michael T Lohr, 2018, Anticoagulant rodenticide exposure in an Australian predatory bird increases with proximity to developed habitat, Sci Total Environ
- How Much Does a Rat Exterminator Cost? (2021) – This Old House, This Old House