Why do I hear scratching in my walls and ceiling at night?

Rats are nocturnal and travel through wall voids, plumbing chases and the gaps between ceilings and walls after the building goes quiet, so you hear scratching, gnawing and scurrying at night while the rat itself stays hidden. In NYC's attached buildings the sound seems to move around because the voids connect. Consistent night noise is a reliable sign of activity even without a sighting.

How do rats get into walls and ceilings in a NYC building?

Through the building envelope. Rats enter via gaps around pipe and utility penetrations, vents, foundation cracks and gaps under doors, then travel up plumbing chases and through wall voids to the spaces between ceilings and floors. Mice can fit through a hole the width of a pencil and rats through a slightly larger gap, which is why sealing those openings is the core of getting them out.

Is it rats or mice in my ceiling?

Size of the evidence is the clue. Rat gnaw marks measure about 3.5 to 4 millimeters wide versus 1 to 2 millimeters for a mouse, and rat droppings are far larger than a mouse's rice-grain droppings. Heavier scratching, larger gnaw holes and bigger droppings point to rats; fine, light nibbling and tiny droppings point to mice.

Why do commercial buildings and restaurants get rats in the ceiling?

Commercial kitchens and food-service spaces offer constant food and warmth, and their drop ceilings, shared party walls and utility chases give rats hidden highways to travel and nest above the dining or prep area out of sight. That's why a ceiling rat problem in a restaurant or retail space needs an exclusion-and-trapping program that treats the whole structure, not just the room where they were heard.

Can I get rats out of my walls myself?

You can trap down some of the population, but the lasting fix is sealing every entry point in the building envelope, which is hard to do completely in a shared NYC building where the voids connect to neighbouring units. If the noise persists, droppings appear in several rooms, or it's a multi-unit or commercial building, the source is usually beyond your unit and needs a building-wide response.

Rats in Walls and Ceilings in NYC: Sounds, Signs and How to Get Them Out

The short answer

Rats get into NYC walls and ceilings through gaps in the building envelope, then travel through wall voids, plumbing chases and the space above drop ceilings — so getting them out means trapping down the population and sealing every entry point. Rats can make nests inside walls and other protected places (Cornell IPM), and in New York’s connected, party-walled buildings, killing rats without sealing how they get in just invites the next wave.

The sounds and signs of rats in walls and ceilings

The most common first sign is sound. Rats are nocturnal, so New Yorkers report the same thing over and over: scratching, gnawing and scurrying inside walls and ceilings at night, but never a rat in sight. In NYC’s attached buildings, rats travel through shared wall voids, between joists and up plumbing chases, so the noise seems to move around the room.

Beyond the noise, look for:

Gnaw marks. Rats gnaw constantly. Adult rat gnaw marks measure about 3.5 to 4 millimeters wide, versus 1 to 2 millimeters for a mouse (Cornell IPM) — a quick way to tell which rodent you have.
Droppings along travel routes, in cabinets, and dropping from ceiling gaps and light fixtures.
Greasy rub marks where rats brush fixed surfaces on their runways.
A musky, ammonia-like odor from urine and nesting in the void, or a sudden decay smell if a rat dies in an inaccessible space.

For the full identification checklist, see signs of rats in your NYC home.

Why NYC buildings funnel rats into walls and ceilings

New York’s building stock is almost designed to move rats through walls and ceilings. Party walls shared between attached brownstones and row houses give rats continuous voids that run from one building into the next. Plumbing and utility chases act as vertical highways between floors — rats follow pipes up from the basement into upper-floor walls and ceilings. And drop ceilings, common in commercial spaces, basements and renovated apartments, create a wide, dark, hidden cavity above the room that rats use to travel and nest out of sight.

Rats exploit all of this through the building envelope. They enter via gaps around pipe penetrations, vents, foundation cracks and doors, then work into the voids. The gaps don’t need to be large: mice can fit through a hole the width of a pencil (about a quarter inch), and rats need only a modestly larger opening (CDC). Norway rats — NYC’s dominant rat — prefer to burrow in soil but will take advantage of voids near a food source (Cornell IPM), which is exactly what a heated wall above a kitchen offers.

Commercial buildings, restaurants and ceiling rats

For a commercial property — a restaurant, bodega, retail space or office — ceiling rats are a particular problem. Commercial kitchens provide constant food and warmth, and their drop ceilings, shared party walls and utility chases give rats hidden routes to travel and nest directly above the prep and dining areas. You’ll often hear them in the ceiling before anyone sees a rat, and a sighting in a food-service space is a Department of Health concern, not just a nuisance.

A commercial ceiling rat problem can’t be solved by trapping the one room where rats were heard. Because the voids connect across the structure and into neighbouring units, it needs a whole-structure exclusion-and-trapping program: inspect the building envelope and the ceiling cavity, trap down the active animals, and seal every penetration rats use to reach the void. That’s the approach our rat & mouse control service runs for food-service and commercial clients, with the documented service records inspectors expect.

How to get rats out of walls and ceilings

The lasting fix is always the same two-part approach — knockdown plus exclusion:

Confirm and locate. Use the night sounds and the signs above to confirm rats and trace where they’re travelling.
Trap down the population. Set snap traps and tamper-resistant bait stations along walls and runways, away from children and pets, to remove the rats already in the voids.
Seal every entry point. Fill small holes with steel wool and caulk around it; close larger holes with lath screen, hardware cloth, metal sheeting or cement (CDC).
Think building-wide. In a shared NYC building the voids connect to neighbouring units, so a complete seal often needs a building-level response.

For the prevention-first version of this — sealing the envelope before rats establish — see how to rat-proof your NYC home.

When to call a professional

If the scratching persists, droppings turn up in several rooms, or it’s a multi-unit or commercial building, the source is beyond your unit — rats are using shared voids and chases your traps can’t reach. Our rat & mouse control service inspects the whole building envelope and ceiling cavity, finds and seals the entry points DIY misses, and knocks the population down across the building — not just the one room where you heard them.