Why rodent control here is a block-level problem
A rat colony is a neighborhood resident. It burrows in whatever soft ground is available, feeds wherever food is easiest, and moves a few hundred feet between the two. In Philadelphia, with small yards backing onto each other and trash staged on a common schedule, that radius takes in a dozen properties. That is why the cleanest house on the row can still have rats at the cellar door. Your own housekeeping controls whether they find a reason to stay, not whether they show up. What works is doing your own part properly and pushing on the shared part. On your property: hard-sided trash containers with lids, set out as late as the rules allow, no pet food outdoors, clutter cleared so burrows are visible, and every grade-level opening closed. Beyond it: talk to the neighbors on both sides, since sealing one house in a row of open ones mostly redirects traffic. Where a business or a vacant property is generating the pressure, that is the conversation worth having with the city.
Mice and shared walls in attached housing
Mice in attached homes behave less like invaders and more like commuters. They travel through the voids in party walls, up the chases cut for risers, and out into a room through the gap around a drain pipe under the sink. A quarter of an inch is enough, so most of these routes look like nothing at all. This is why a homeowner can trap steadily and still get replacements. The animals are not coming in from the street, they are coming from the building next door, and the trap line has no effect on that supply. The fix is small-scale and cheap per opening. Pull the escutcheons and access panels in the kitchen and bathroom, pack every penetration tight with copper mesh, and seal over it. Do the same behind radiators and at any hole cut for cable or gas. Then trap. If your neighbor is willing to do the same at the same time, the whole row benefits, and if not, sealing still turns your home from a corridor into a dead end.
Old buildings, old holes and what a real inspection finds
Buildings that have been altered for a century collect openings the way an attic collects boxes. Coal chutes get bricked up imperfectly. Gas lines are abandoned in place, leaving the hole. Plumbing gets replaced and the old penetration never gets closed. A joist pocket in a stone foundation opens up as mortar fails. A proper first visit is a hunt for those. Expect the technician to spend most of the appointment in the basement and around the exterior at grade: the sill line, window frames and wells, the cellar door and its threshold, floor drains, and the joint where a rear addition meets the original wall. Photographs should come back with them. What you should be handed is short and specific: which species, a list of openings with the material chosen to close each, a trapping schedule with a number of visits, and any cleanup priced separately. If nobody opened the basement and the recommendation is a monthly exterior station, that is a service subscription rather than a repair, and it is worth getting a second opinion before you sign.
Cellars, storms and standing water
Water shapes rodent behavior in this city more than people realize. Shallow groundwater and roughly 47 inches of annual rain mean cellars take on moisture regularly, and a wet cellar is attractive to Norway rats for the same reason it is unpleasant for you. After a heavy storm, two things happen at once. Burrows flood, displacing animals into buildings, and any floor drain that has lost its grate becomes an open doorway once the water recedes. Both are reasons a building that was quiet in August gets loud in September. Build an inspection habit around weather instead of the calendar. After a major storm, look at cellar corners, behind stored material and around the drains. Keep storage on shelving so evidence appears early. And treat standing water as part of the pest problem rather than a separate maintenance item, since contaminated water is the exposure route for leptospirosis and the CDC lists rodents among the carriers. Dry the space out and the building becomes far less interesting to them.
Reading an estimate and knowing what you bought
Rodent quotes in Philadelphia vary widely for the same building, and the difference is usually what got included rather than who is better. Lay two side by side and look for four items priced separately: the inspection, the sealing work, the number of trapping visits, and any cleanup. A low bid built on exterior bait and a monthly fee holds numbers down while you keep paying and closes nothing. A bid listing ten sealed openings with the material named for each is a repair with an end date, and it will cost more this year and less over five. Ask each company the same short list. What did you find and can I see the photos. What material closes each opening, since anything softer than metal or mortar eventually gets gnawed. How many return visits are included. Does the price cover the yard and the trash area. Get the winning plan in writing before work begins, then walk the list of sealed openings yourself before the final payment goes out.