Chicago rodents head indoors as soon as the nights cool off. Here is how owners inspect, seal, and garbage-proof a building before the fall push begins.
Chicago consistently ranks at or near the top of national rat rankings, and the pressure is seasonal. Through the summer, Norway rats and house mice live comfortably outdoors, in alley burrows, under wooden back porches, and in overgrown gangways. Once overnight temperatures start dropping in September, that outdoor population goes looking for somewhere warm and dry with a reliable food source, and a heated apartment building is exactly that.
For owners in Logan Square, Wicker Park, and Bucktown, where dense two-flats and three-flats share narrow gangways and a common service alley, one neglected building can seed an entire block. The window that matters is late August through early October. Exclusion work done now costs a fraction of what a midwinter infestation costs in extermination, tenant goodwill, and 311 complaints, and it is far easier to seal a foundation gap before the ground freezes.
Trapping without exclusion is a treadmill. Start with a slow lap around the building at ground level, ideally with a flashlight, looking for entry points rather than for animals. A house mouse fits through a gap about the width of a pencil. A Norway rat needs roughly the size of a quarter.
Check where utility lines, gas service, and cable conduits penetrate the foundation, since those are the most common openings in Chicago greystones and frame two-flats. Look at mortar joints at grade, the gap under garage service doors, crawlspace vents, and the junction where wooden back porch framing meets masonry.
Note the active signs too: smooth dark rub marks along foundation walls, fresh burrow holes near the gangway or under the rear stairs, and droppings around the garbage cart pad. Photograph each opening and mark it with chalk or tape so nothing gets missed on repair day.
Expanding foam on its own is not exclusion. Mice chew through it in a weekend, and rats do it faster. Use materials with real mechanical resistance.
Copper mesh or stainless steel wool packed tightly into a gap and then capped with mortar, hydraulic cement, or a quality sealant will hold. For larger foundation openings, quarter-inch galvanized hardware cloth cut oversized and fastened with masonry screws is the standard fix. Gaps under exterior doors need door sweeps with a metal-reinforced edge. A worn rubber sweep on a rear service door is one of the most common failures we find in Rogers Park and Ravenswood buildings.
Do not stop at ground level. Rats climb, and older buildings often have openings at soffit returns, around roof vents, and where a fire escape bolts through masonry. If a squirrel could use the opening, a rat can use it too.
Contact Lena Services INC at 773-939-4284 or [email protected]