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.
