New York City has one of the densest rodent populations in the world. Aging infrastructure, restaurant-heavy blocks and continuous construction give rats and mice food, shelter and highways between buildings. Killing the rodents you can see is only half the job — without sealing how they get in, the next wave moves in within weeks.
Our rodent programme is built around exclusion: we inspect the building envelope for gaps around pipes, vents, foundation cracks, door sweeps and utility penetrations — rats can squeeze through a hole the size of a quarter, mice through a dime. We seal those entry points, then knock down the active population with a combination of trapping and tamper-resistant baiting placed away from people and pets.
For restaurants, bodegas and multi-family buildings we also advise on sanitation and storage, because rodent pressure in NYC is relentless and a one-time knockdown won't hold without addressing what's drawing them in.
NYC rats are a documented public-health issue, not just a nuisance. The city's dominant rodent is the brown rat (Norway rat, Rattus norvegicus), and a 2023 study estimated roughly 3 million of them across the five boroughs. These rats carry pathogens that reach people: a 2014 Columbia University study of Manhattan rats found Salmonella and E. coli, Seoul hantavirus, and Leptospira, and NYC Health reported a record 24 human leptospirosis cases in 2023, rising to 33 in 2024 — far above the 2001–2020 average of about three cases a year. Most exposure comes from contact with rat urine and droppings, which is why eliminating an infestation and cleaning contamination safely is genuinely protective, not optional.
New York's own rat-control infrastructure tells you how seriously the city takes this. The Health Department conducts more than 150,000 rat inspections a year, designates high-burden neighborhoods as Rat Mitigation Zones, and 'indexes' every property in targeted areas; the Sanitation Department's trash-containerization push has driven 311 rat-sighting complaints down and pushed inspections with active rat signs to a five-year low of 19.7% in FY2025. For a property owner or business, that environment means two things: rat pressure is being squeezed citywide, but a property with active signs or open trash can still be cited. Our programs are built to get a property past inspection — treating the colony, collapsing burrows, and removing the conditions inspectors look for.
What every NYC property owner should know about rats — and the City rules that govern them
NYC's Health Department designates Rat Mitigation Zones — neighbourhoods with high rat activity, like Harlem since January 2023 — where City agencies concentrate abatement resources. Residents report rats and check a property's inspection history through 311 and the Health Department's Rat Information Portal, so a documented professional programme is what keeps a building off the City's radar. (NYC DOHMH — Rat Mitigation Zones)
Under NYC rules, property owners are legally required to keep their properties rat-free and fix the conditions that attract rats. The Health Department states that when owners do not meet this legal requirement, tenants can report the problem through 311 and the Department sends inspectors to investigate — so an active infestation is a compliance exposure, not just a nuisance. (NYC DOHMH — Rats: Information for Tenants and Property Owners)
The Health Department's inspection terms set out the enforcement cycle: an Initial Inspection fails on any Active Rat Signs — fresh burrows, runways, rub marks or gnawing — and on harborage such as clutter and dense vegetation, after which a Compliance Inspection follows. That makes removing harborage, not just killing rats, the owner's burden. (NYC DOHMH — Rat Inspections: Terms and Practices)
The CDC's guidance puts exclusion first: mice can squeeze through a gap the width of a pencil — about a quarter inch or 6 millimetres — so small holes should be sealed with steel wool and caulk and larger ones with lath screen, cement or hardware cloth. In old NYC building stock, this seal-up step is what baiting alone cannot replace. (CDC — Seal Up to Prevent Rodents)
Exclusion-first vs baiting-only for NYC rats
| Exclusion-first (seal-up + harborage removal) | Baiting-only | |
|---|---|---|
| Targets the actual NYC violation | Yes — removes the harborage and entry points the Health Department inspects for | No — bait stations do not clear harborage or burrows |
| Stops re-entry through gaps | Yes — seals the pencil-width gaps (CDC) rats and mice follow along walls | No — kills some rats but leaves the openings open |
| Addresses Norway-rat behaviour | Yes — closes the burrows and wall/riser runways they reuse | Partial — burrows and runways stay active |
| Disease-exposure reduction | Higher — fewer rats and less urine contamination (leptospirosis risk per DOHMH) | Lower — contamination persists while the colony rebuilds |
| Durability after treatment | Long-term — physical barriers remain in place | Short-term — survivors and newcomers repopulate |
Signs you have a rodent control problem
- Droppings along walls, under sinks, or in cabinets and drawers
- Gnaw marks on food packaging, wiring, or baseboards
- Scratching or scurrying noises in walls or ceilings, especially at night
- A persistent musky, ammonia-like odour
- Greasy rub marks along baseboards and runways
Why Carroll Gardens sees this
NYC's connected basements, shared trash areas and subway-adjacent blocks mean rodent control has to think about the whole building and the street, not just one apartment.
We help commercial clients stay ahead of NYC Department of Health inspections, where rodent evidence is a common violation.
NYC's brown rats are burrowing rodents — they nest in soil along foundations, in tree pits, garden beds, and under decking and slabs — so effective control in the city means treating and collapsing outdoor burrows, not only setting indoor traps.
If your building sits in a NYC Health Department Rat Mitigation Zone, every property in the area can be inspected (indexed), and active rat signs or uncontained trash can trigger a Commissioner's Order to Abate — we document treatment and proofing to keep you inspection-ready.