Summarize:

Make sure that your trash is not a rat buffet. Rats have trouble chewing through metal or thick plastic bins, but they can easily enter a container with an open lid. If they make a home in the trash, they're more likely to come inside the building as well. If you or your tenants improperly store food, then rats are more attracted to your building. Food should not be stored in dark, closed areas where rats can be easily active. Additionally, food shouldn't be left sitting out. Don't store food in the basement. This includes pet food. Encourage good pet food habits amongst your tenants. Food should not be left out. Leaky pipes offer a water source, and damaged systems offer a place for rats to hide. Keep them out by doing regular maintenance and fixing any issues immediately. Stop rats from entering the building in the first place by keeping your building and foundation secure. Rats can squeeze through the tiniest of cracks, so even a hole as small as a dime needs to be repaired. Carefully inspect and repair your walls, roof, and foundation. Check close to the ground for freshly dug holes. Rats sometimes dig near the foundation so that they can crawl through to the inside of the building. If your walls or basements have vent openings, the rats can enter through the slats or holes. While you can't block the opening, you can apply wire mesh over the open slats so that the rats cannot enter. You can use steel wool to fill in gaps around vents or pipes. Windows provide rats with an open opportunity to enter a building, but it's unreasonable to expect people to leave their windows shut at all times. Instead, make sure that every window has an undamaged screen. Ask tenants to regularly inspect their screens for holes and slits. Offer to replace screens at no cost to them. Rats can squeeze under gaps at the bottom of the door. If your apartment building has doors that leave a gap between the door and the jam, then install a door sweep. The door sweep will attach to the bottom of the door, providing a seal against outside intruders. Rat can hitchhike in large deliveries, especially if food is involved. Rats love to hide in wood piles, garbage, discarded items, and tall grass.
Secure the lid to the trash bin. Use safe food habits. Maintain plumbing systems. Repair cracks and holes. Block the area around pipes and vent openings. Cover all windows with a wire screen. Add door sweeps. Encourage tenants to carefully inspect deliveries. Remove any debris from around the building.