It seems to me that questions concerning habitability and the effect lack of habitability are asked often both by landlords and tenants. Specifically, landlords ask what are they required to do with respect to habitability, and tenants ask what they can do if the landlord fails to meet these requirements.
With respect to the landlord, the general rule is that he is responsible to maintain the rented premises in a habitable condition. Also he is required to act “reasonably” when a habitability problem arises. As regards the tenant, responsibility for the habitability problem rests with the tenant if it is caused by the tenant. It should be kept in mind, thought, that the two concepts are not mutually exclusive. Even if the tenant is the cause of the cockroaches, for example, the landlord is not excused from eradicating them in a prompt an reasonable manner. Conversely, in this same situation, neither is the tenant excused if the landlord takes care of the problem. In other words, the tenant must reimburse the landlord for the expense of eradicating the cockroaches and can be evicted if he fails to do so.
So in the real world, the tenant complains to the landlord that he has cockroaches or that the screens in the apartment are broken. After promptly investigating, the landlord determines that the tenant’s own lack of cleanliness is the cause for the cockroach infestation and that the tenants kids pushed out all of the screens. What is the landlord required to do in this case? First, he should inform the tenant that the tenant is responsible for both habitability issues and he should demand that the tenant promptly remediate. If the tenant fails to do so within a reasonable time (which almost always is the case), then the landlord must take care of the problems himself. The landlord now has acquitted himself of his responsibilities with respect to the habitability complaints.
But the story is not quite over. The next question is, what can the landlord to about this? The simple answer is he can evict the tenant, upon service of the proper notice, or he can simply file a small claims action for the cost of remediation and repair.
On the other hand, what can the tenant do if the landlord fails to send out an exterminator and to repair the screens? In California, there are multiple remedies from which the tenant can choose: repair and deduct, withholding of all or part of the rent, terminating the lease, and even suing the landlord. These remedies require a substantial knowledge of the law and experience with how the courts deal with these situations. In other words, they required the assistance of competent counsel and careful consideration.