Letter Telling the Landlord You Intend to Repair and Deduct
From California Tenants Rights, "Withhold the Rent If problems are serious and other attempts to repair them have failed, you may be able to stop paying any rent to the landlord until the repairs are made. Before you can properly withhold the rent, be sure that you can say “Yes” to the questions in “Big Stick Prerequisites,” above. When you withhold rent, you simply stop paying rent until the landlord fixes the problem (at least two cities, however, have established escrow programs for tenants who withhold rent, as described in Step 1, below). The theory is that the landlord will be powerfully motivated to do the repair when the rent has stopped coming in. Once the rental is habitable, you begin paying rent. You will also owe the landlord a portion of the withheld rent, which reflects the value of the rental in its unfit condition (see “Paying the Landlord for the Value of the Unfit Rental,” below, for methods of computing the proper amount)."
