Why sealing the building is the real fix
Yes, usually. Sealing the gaps and holes rodents use to enter — around pipes, vents, foundations, and doors — is generally part of the landlord's duty to keep the building sound and free of rodents.
Trapping the rodents already inside is only half the job. If the entry points stay open, new rodents keep coming and the infestation never really ends. Because these openings are part of the building's structure, closing them off — a process pest professionals call exclusion — is typically the landlord's responsibility.
A landlord who only sets traps but ignores the holes is treating the symptom, not the cause, and the problem will usually return. Lasting control almost always requires both removing the current rodents and sealing the building. If your landlord sets traps but never seals the entry points, a free review can help you understand what more they should be doing.
This is general information about California tenant rights, not legal advice. Every situation is different.