(a) If within a reasonable time after written or oral notice to the landlord or his agent, as defined in subdivision (a) of Section 1962, of dilapidations rendering the premises untenantable which the landlord ought to repair, the landlord neglects to do so, the tenant may repair the same himself where the cost of such repairs does not require an expenditure more than one month’s rent of the premises and deduct the expenses of such repairs from the rent when due, or the tenant may vacate the premises, in which case the tenant shall be discharged from further payment of rent, or performance of other
conditions as of the date of vacating the premises. This remedy shall not be available to the tenant more than twice in any 12-month period.