How do mice get into a NYC apartment in the first place?

Through gaps as small as 6mm — roughly the diameter of a pencil. The most common entry points in NYC apartments are the gaps around water supply pipes and drainpipes under the kitchen and bathroom sink, the space where the gas pipe enters the wall behind the stove, gaps at the base of walls where the floor meets the baseboard, worn door sweeps or gaps under exterior-facing doors, and pipe chases inside shared walls that run vertically from the basement to upper floors. In prewar buildings — the majority of NYC's residential stock — these penetrations were never properly sealed during construction.

I live on the 8th floor. How do mice even reach my apartment?

Through the building's internal pipe risers and wall cavities. Hot water lines, plumbing stacks, and electrical conduit run vertically through every floor from basement to roof. Mice use the gaps around these pipes as internal vertical travel routes. A ground-floor or basement breach can establish a population that colonises upper floors within four to six weeks via riser penetrations at each floor. The mouse you found on the 8th floor almost certainly did not take the elevator — it travelled vertically through a wall cavity.

What is the most effective mouse trap for a NYC apartment?

Standard snap traps — Victor, Tomcat, or equivalent — remain the most effective and the most humane option. They kill instantly, are cheap, and are easy to monitor daily. Set them in pairs flush against the wall, not perpendicular to it, because mice run along walls rather than across open floor. Bait with a pea-sized amount of peanut butter, hazelnut spread, or chocolate. Place traps at every location where you have found droppings. Glue boards are not recommended — they are inhumane, slow to kill, and do not address the entry problem. Electronic traps work but cost significantly more for equivalent effectiveness.

Is poison bait safe to use in a NYC apartment?

No — for two reasons. First, in an apartment with pets or children, rodenticide bait poses an accidental ingestion risk that is not acceptable. Second, mice poisoned inside a wall die inside a wall. Decomposing mice in wall cavities produce a foul odour that can persist for weeks, is extremely difficult to locate, and is impossible to remove without opening the wall. Snap traps are the correct method for apartment use — dead mice are caught on the trap, visible, and disposable immediately.

My landlord is not doing anything about the mice. What are my rights in NYC?

Under NYC Housing Maintenance Code §27-2018, your landlord is legally required to maintain your apartment free of mice and other pests. Mice are classified as a Type C (hazardous) violation, which requires the landlord to remediate within 30 days of HPD inspection. If HPD classifies the infestation as immediately hazardous, the timeframe drops to 24 hours. Steps: notify your landlord in writing (text message or email with timestamp is sufficient), keep a record of sightings with dates and photos of droppings, then file a 311 complaint if no action is taken within a reasonable window (72 hours for an active infestation is reasonable). HPD will inspect and issue violations. Your landlord — not you — is responsible for the cost of extermination in a rental.

How do I know if I have one mouse or an infestation?

One mouse seen equals 10 to 50 mice living in your wall voids — that is the pest-control industry standard and it reflects how mouse biology works. The mouse you saw is the bold one, the hungry one, or the one pushed out of the nest by competition. A single female produces 50 to 75 pups per year across multiple litters of 6 to 8 young, with offspring reaching sexual maturity in six weeks. Signs of an active infestation beyond a sighting: dark shiny droppings (fresh) or grey chalky droppings (older) concentrated along walls and in cabinet corners; grease rub marks — dark smears on baseboards where mice repeatedly travel the same path; gnaw marks on food packaging, cardboard, or wiring insulation; scratching sounds in walls at night. If you see mice during daytime, the population is large enough that competition for space and food is pushing individuals into open areas during unusual hours — that requires professional intervention.

When should I call a professional exterminator for mice in my NYC apartment?

Call a pro if: you find an active nest (shredded paper or fabric, multiple young, heavy dropping concentration in one location); you see mice during daytime, which indicates a significant infestation; you have set snap traps correctly for two weeks and the catch rate is not declining; or you live in a shared building and the mice appear to be coming from common walls or areas outside your unit, which makes DIY-only resolution structurally impossible. For NYC renters: your landlord should be funding this, not you — see the question on tenant rights above.

What is the best food storage practice to prevent mice?

Transfer everything not in a glass jar or steel tin into airtight hard-sided containers. Mice chew through cardboard cereal boxes and thin plastic bags without resistance — those are not mouse-proof storage. The target is any food that has a scent: grains, pasta, flour, rice, pet food, snacks, bread. Under-sink cabinet space near pipes is an active mouse travel route — keep it completely clear of food. Clean up crumbs from counters and floors nightly, and do not leave pet food out overnight.

How to Get Rid of Mice in Your NYC Apartment

Step 1: Find Every Entry Point Before You Set a Single Trap

Trapping without sealing is treadmill pest control. You catch a mouse, another enters through the same gap the next night. The only way to stop this cycle is to eliminate the entry points first.

Mice enter through any gap larger than 6mm — roughly the diameter of a pencil. In NYC apartments, the locations to check are:

Under the kitchen sink: The gaps around hot and cold supply pipes and the drainpipe where they enter the wall. In most NYC apartments these gaps are partially or completely open.
Behind the stove: The gas supply pipe penetration. Pull the stove out and check the wall behind it.
Bathroom plumbing penetrations: Supply pipes and drainpipes under the bathroom vanity; the gap around the toilet’s supply line; gaps at the base of the bathtub.
Baseboard gaps: Anywhere the baseboard has separated from the floor or the wall, particularly in corners.
Door sweeps: If daylight is visible under your front door or any exterior-facing door when closed, mice can enter.
Behind the refrigerator: Pull it out. The wall behind older NYC refrigerators often has open pipe chases from the building’s water supply.
In closets: Check corners at floor level, particularly in closets that share a wall with another unit or a building corridor.

Use a torch and get down to floor level — entry points at skirting height are easy to miss at standing height. Push a small piece of newspaper into any gap you find so it holds position, then walk through after dark: in active infestations you can sometimes hear mice moving paper you’ve placed at active entry points.

Step 2: Seal the Gaps With the Right Materials

Expanding foam alone is not a mouse barrier. Mice chew straight through cured expanding foam — it takes them less than a minute. The correct approach is:

Copper mesh (Xcluder) or steel wool: Pack it firmly into the gap before applying any sealant. Mice cannot chew through copper mesh or steel wool. Fill the gap completely — if the gap is large, use multiple passes.
Expanding foam over the mesh: Apply over the packed mesh to hold it in place and create a finished surface. The foam adds no mouse resistance on its own; it anchors the mesh.
Hardware cloth (galvanised steel, 1/4-inch mesh): For larger openings — gaps under kick plates, large pipe chases, or structural openings — hardware cloth fixed with screws or construction adhesive is the correct closure. Available at any hardware store in NYC.
Door sweep: If your front door has a daylight gap, a door sweep is a $15 fix. Metal-reinforced rubber sweeps are better than standard rubber-only versions.

Do not use caulk alone for any gap larger than 2mm. Mice can re-open dried caulk.

Step 3: Set Snap Traps Correctly

After sealing, set snap traps at every location where you found droppings. Placement and quantity matter more than trap brand.

Placement: Flush against the wall, with the trigger end toward the wall. Mice run along walls — a trap set perpendicular to the wall, or in the middle of the floor, will catch far fewer mice. The mouse travels along the wall, encounters the bait end of the trap, and triggers it.

In pairs: Set two traps side by side at each active location, triggers facing in opposite directions. Mice sometimes step over a single trap. Two traps at the same spot doubles catch rate.

Bait: A pea-sized amount is enough. Peanut butter is the most effective NYC bait — it stays on the trigger, mice cannot steal it without engaging the mechanism, and the scent carries. Hazelnut spread (Nutella) and small pieces of chocolate also work. Do not use cheese — the stereotype is wrong; cheese is not particularly attractive to mice and falls off triggers easily.

Check daily: A snapped trap with no mouse means a mouse triggered it without being caught — reset it. A mouse on a trap should be removed within 24 hours. Dead mice left on traps or nearby reduce trap effectiveness as other mice avoid the scent.

How many traps: More than you think. Pest control professionals place a minimum of six traps per room in an active infestation. Three or four traps spread across an apartment is unlikely to be sufficient. Focus density in the kitchen and any room where you have found droppings.

Step 4: Secure Every Food Source

An apartment with sealed entry points and active traps but accessible food will simply sustain a smaller mouse population rather than eliminate it. Mice can survive on 3 grams of food per day.

Relocate to hard-sided containers:

Dried grains, pasta, rice, flour, oats
Bread and crackers
Pet food — never leave out overnight
Snacks in cardboard or thin plastic packaging

Glass jars with screw lids, sealed plastic containers with locking lids, and steel tins are all mouse-proof. Cardboard, foil packaging, and thin plastic bags are not.

Garbage: Use a metal or hard-plastic lidded bin inside the apartment. Do not leave open bags of rubbish on the floor overnight.

Under the sink: Clear this space entirely of food products. Under-sink cabinet space in NYC apartments is a primary mouse travel corridor — food stored there is highly accessible to mice and also reduces your ability to inspect and seal pipe penetrations.

Step 5: Know Your Landlord’s Legal Obligation

If you rent your apartment, mice are not your financial problem to solve. Under NYC Housing Maintenance Code §27-2018, your landlord is required by law to maintain your building free of pests including rodents. Mice in a rental unit constitute a housing violation — specifically a Class C (hazardous) violation when an active infestation is present.

What to do:

Notify your landlord in writing. A text message or email with a timestamp is sufficient. Keep the record. Say clearly: “I have an active mouse infestation in my apartment. I am requesting extermination and repair of entry points as required under NYC Housing Maintenance Code §27-2018.”
Document. Photograph droppings with timestamps. Keep a log of sightings — date, time, location. This documentation supports a 311 complaint if your landlord fails to act.
File a 311 complaint if the landlord does not respond within 72 hours of a written notice for an active infestation. HPD will schedule an inspection and can issue violations.
After HPD issues a violation: A Class C violation requires the landlord to remediate within 30 days. If HPD classifies the condition as immediately hazardous — which can apply to a severe infestation — the landlord has 24 hours to begin remediation.

You are entitled to pest-free housing as a baseline. You should not be paying for exterminator visits or traps in a rental — document, notify in writing, and escalate to 311 if your landlord does not act.

Step 6: Coordinate With Neighbours in Shared Buildings

In an NYC apartment building — whether a prewar walk-up, a postwar co-op, or a high-rise — mice travel through shared wall voids, pipe chases, and building corridors between units. Treating only your apartment while neighbouring units remain active accomplishes less than it should.

Mice do not stay in one unit. They redistribute within four to six weeks into adjacent spaces through the same internal routes they used to arrive. If your neighbour on the same floor, directly above, or directly below has an active infestation, your sealed-and-trapped apartment will face ongoing re-ingress pressure.

What this means practically:

Talk to your neighbours. If others on your floor or in adjacent units have seen mice, that information is relevant to how aggressively you need to seal your unit — and to what you report to your landlord.
If your building has a super, a mice problem reported by multiple tenants on the same floor is much more likely to result in building-wide treatment than a single-unit complaint.
If your super or landlord treats your unit in isolation and the problem returns within a few weeks, the source is likely a neighbouring unit or a common area (basement, laundry room, building corridor). At that point, a building-wide treatment is the correct escalation — and it is your landlord’s responsibility to provide it.

Step 7: When to Call a Professional

DIY treatment is effective for early-stage, single-unit mouse problems when combined with proper exclusion. Call a licensed NYC pest control professional if:

You find a nest. An active nest with young mice indicates an established population. Professional inspection is needed to assess the full extent before treatment.
You see mice during daytime. Mice are nocturnal. Daytime sightings indicate a population large enough that competition for resources is pushing individuals into open activity during unusual hours.
Trapping is not working after two weeks. If you have sealed entry points, placed traps correctly, and are still catching mice consistently after two weeks without a decline in catch rate, the entry points were not fully sealed or the population is larger than DIY treatment can resolve.
The problem is building-wide. If droppings appear in common areas, the building super is ineffective, and multiple neighbours are affected, a licensed operator can assess and treat the full building — something no individual tenant can do.
You are a renter and your landlord is unresponsive. A professional inspection report documenting the infestation and entry points is useful evidence for an HPD complaint and any follow-on action.

A licensed NYC pest control company will inspect with UV light (fresh droppings fluoresce), map grease rub marks along active travel runways, identify every entry point, seal with copper mesh and hardware cloth, set snap traps at active zones, and monitor weekly for a minimum of four weeks. Two consecutive weeks with zero catches and sealed entry points indicates resolution.