there shall be rule regarding this depends on the state.

Here is the property code from my state regarding similar situation:

 

If after a casualty loss the rental premises are partially

unusable for residential purposes and if the casualty loss is not

caused by the negligence or fault of the tenant, a member of the

tenant's family, or a guest or invitee of the tenant, the tenant is

entitled to reduction in the rent in an amount proportionate to the

extent the premises are unusable because of the casualty, but only on

judgment of a county or district court. A landlord and tenant may

agree otherwise in a written lease.