Why are there rats in my Tampa attic?

Why roof rats and not the rats from the drains?

Roof rats live above ground, which is why an attic, not a sewer or a yard, is the place they choose to nest.

The rat most people picture is the one that lives in drains and burrows under a yard. That is not the animal usually found in a Tampa attic. The roof rat, Rattus rattus, is a climbing species, and UF/IFAS describes it as the worst and most abundant rodent pest in Florida. It nests in roof spaces, in the upper parts of trees and in dense shrubs, and it moves along wires, branches and fences to get where it wants to go.

The Norway rat, which is the burrowing species, is described by UF/IFAS as rare in Florida. That matters for a homeowner because the signs, the routes and the fix are different. A rat in an attic is almost always a roof rat, and the fix is above the ground, not in the drains.

What are the signs in an attic or roof space?

Sound, droppings, gnaw marks and smears are the signs that matter most, and they are usually found together.

Roof rats are most active at night, so the first sign is often a sound rather than a sight. Scratching or light running across the ceiling joists, heard after dark or early in the morning, is a common first clue. The droppings follow, usually along the top of the ceiling, near stored boxes and close to the spots where the animal feeds or rests.

Gnaw marks are the sign that deserves the most attention. Roof rats chew to keep their teeth worn down, and they will chew wood, insulation, cardboard and wiring. The list below sets out what to look for, and it is worth a walk through the attic with a flashlight before anyone decides the building is clear.

• Scratching or running sounds in the attic, mostly at night
• Droppings along the top of the ceiling joists, near stored boxes and the insulation
• Gnaw marks on wood, on wire insulation and on pipe jackets
• Grease or dirt smears along the same routes the animal uses repeatedly
• Shredded nesting material in the insulation or inside stored items

Where do they come in?

The entry is usually above the ground, along a route the animal already uses to climb.

A roof rat does not need a hole in the ground. It needs a way up, and a palm frond or a shrub against the wall provides one. Once it reaches the roofline, it needs a gap at the eave, the soffit, a vent or a pipe penetration, and many houses have one or more of these that have been damaged or left open. The entry is often hard to see from below, which is why the route up the outside matters as much as the attic inside.

Walk the outside of the building with the sound of the attic in mind. Look for the places where something touches the roof or the wall, and for any gap that a rat could use to get in. A technician will check each one.

• Palm fronds that touch the roof or the wall
• Shrubs and vines growing against the eaves or the soffits
• Gaps where a pipe or cable enters the roof or the wall
• Damaged vent screens and loose soffit boards
• Overhanging branches near the roofline

Why do palms and shrubs matter so much?

Palms and dense shrubs give roof rats a climbing route and a nest site outside the building, which is why they are so often the cause.

A palm is a natural ladder for a roof rat. Its fronds reach the roof, its trunk gives cover, and its crown can hold a nest well above the ground. The same is true of dense shrubs and vines that climb the wall. Removing the route is often the most useful step a homeowner can take, and it is the step that keeps a trapped building from being refilled from the trees.

Trimming a palm or a tall shrub can be dangerous, particularly near power lines or on a steep roof. Keep the work on the ground where it is safe, and ask a technician or a qualified tree worker to do anything that needs height. A cut frond or a removed shrub also changes where the rats go, so the building should be checked again afterward.

What exclusion looks like, and why trapping alone fails

Exclusion closes the routes; trapping removes the rats already inside. The two work only together.

Trapping is quick, and it gives an immediate result, but it removes only the animals that were in the building when the trap was set. A building that still has an open route will be reached by the next roof rat that finds it. Exclusion is slower, because it means finding and closing every gap and removing the outside cover, but it stops the flow of new animals in.

A proper exclusion job uses durable materials and sound workmanship. Gaps are filled with materials a rat cannot chew through, metal mesh is fitted over vents, and the outside cover is cut back so the building cannot be climbed. Food and nesting material are removed from the attic, and the building is checked again after each change to see whether the animals have found another way in.

• Seal every gap that a rat could use with durable, chew-resistant material
• Fit metal mesh over open vents and damaged screens
• Trim vegetation away from the roofline and the wall
• Remove food, stored material and nesting material from the attic
• Check the outside of the building again after each change

What damage do they leave behind?

Chewing, nesting and droppings are the damage, and each has a cost and a health concern attached.

Chewing is the damage that costs the most. A roof rat chews through insulation, cardboard and wood, and the wiring it chews can fail or start a fire. Nesting material adds to the mess and can block vents, and the droppings and urine collect in the insulation where they are hard to reach.

Droppings and nests are a health concern. Rodents can carry disease, and disturbing dry droppings can release particles into the air. Do not sweep them up dry. Wear gloves, open a window to ventilate, wet the material with a disinfectant and remove it carefully, or ask a technician to clear the space. A disinfectant should be used as its label directs.

When to call a technician

Call when you see signs more than once, when wiring is chewed, or when you cannot find the route in.

One sound in the attic can be a passing animal. Repeated sounds, a second sign of droppings or any gnawing on wiring is the point to stop waiting. A technician will look at the attic, the outside and the route up the trees, and will explain the plan before anything is closed or set.

Call (855) 974-4733 and describe what you have seen and heard, and where. The desk can arrange a visit, and the technician will explain what was found and what the plan covers before any work starts.

How a technician plans the exclusion visit

A proper visit walks the route from the ground to the attic, then closes the building in the order the animals use it.

A technician starts outside, usually with a walk around the building and a look at the trees and shrubs that touch it. The route from the ground to the roof is traced first, because cutting the outside cover is what keeps a closed building from being climbed again. Then the roofline, the eaves, the soffits and every vent and pipe penetration are checked, and each gap is noted for closing.

Inside, the attic is walked with a light to find droppings, gnaw marks and nesting material. The insulation is checked along the routes the animals have used, and the stored items are moved to see what is underneath. The plan that comes out of the visit lists the outside work, the inside cleanup and any trapping, and explains the order they will be done in. None of it should start before the homeowner has seen and agreed to it.

Why the attic is only half of the building

Roof rats use the whole building and its surroundings, so a fix that stops at the attic door leaves most of the route open.

A rat that has been in the attic has often also used the wall voids, the space above a kitchen cabinet and the crawl space at the base of the building. The entry may have been made through a soffit on one side, while the nest is on the other. For that reason the inspection covers the outside of the house as well as the attic, and it asks where the animals appear first, which is often a clue to the route.

Garages and sheds deserve the same attention. A stored box of clothing or a bag of pet food in a garage is a food source, and a shed roof with a palm frond above it is a route. Removing the food and the cover in those outbuildings is part of the work, even though they are not the house.