Legal Question in Landlord & Tenant Law in California

It depends on where the rats are coming in from and why, whether it is a single family dewelling or a multi-unit property, and if it is a multi-unit property whether the rats are in the common areas or the unit. Landlords are responsible for making sure there is no point of entry for rodents, just as for keeping out wind and rain. The landlord is also responsible for the condition of common areas in multi-unit properties, and if there are rats in the common areas that then enter the units, the landlord is responsible for the rats in the units too. However, if the tenant leaves doors and windows, or any other point of entry for rodents open, and especially if they do so and fail to maintian sanitary conditions, including securing garbage and food, then the tenant may be responsible. I had a tenant in my single family rental who kept the back porch door open for their dog to go in and out, and left food in the porch. I think you can guess who won the fight over responsibility for extermination and clean up when the rats moved into the porch and adjacent basement and kitchen areas.