Rodent Exclusion
Finding and closing the openings rodents use.
Resources
Rodent Entry Point Guide for NYC Buildings
The gap that matters is usually not the one you can see. Here is where inspectors look first.
Short answerRodents enter through pipe penetrations, foundation cracks, utility openings, door gaps, vents, roofline gaps and damaged drains. In NYC buildings the cellar or basement is often where several of these meet.
Pipes and Utilities
Water, gas, drain and radiator lines pass through walls and floors, often with oversized sleeves. Cable and conduit entries and meters add more.
Foundation and Ground Line
Cracks in masonry, gaps where the building meets the sidewalk and cellar or areaway doors that do not seal.
Doors, Vents and Roofline
Worn door sweeps, damaged vent screens and roof edge gaps. These reach upper floors.
Drains and Sewer Lines
Broken or open lines and unsealed floor drains. Toilet entry is rare and points to a broken line.
What to Do
Do not plug holes you have not inspected. See rodent exclusion.
Not sure what you are dealing with? An inspection finds the source and sets the scope.
Questions and Answers
Can rats come through pipes?
Rats can use damaged drain or sewer lines, and gaps where pipes pass through walls and floors are a common way in. Coming up through a toilet is rare and usually points to a broken line. An inspection that looks at the lines and every pipe penetration is how you find out which applies to your building.
Why do rodent problems so often start in basements and cellars?
Basements and cellars sit at ground level and hold pipes, utility lines, older masonry, storage and access to trash areas. That combination gives rodents entry, shelter and food in one place. In many NYC buildings the cellar is also where shared utility runs connect to the upper floors, so activity below can show up as noise or droppings above.
What materials are used to seal rodent entry points?
Materials rodents cannot chew through, matched to the opening. That usually means metal mesh or hardware cloth, sheet metal, and cement or masonry fillers for masonry gaps. Foam or plain caulk on its own is not enough because rodents chew it out. The right choice depends on what the opening is, what surrounds it and how it will be used.
Last reviewed 2026-09-21. Time sensitive NYC rules and processes change, so check the linked official pages before you act.
Related pages
Entry Point Sealing
Closing the specific openings an inspection finds.