What are a landlord’s responsibilities regarding repairs?
A landlord must make a rental unit habitable both prior to and during a lease. The landlord is legally required to make all necessary repairs to ensure habitability throughout a tenancy. The case of Green v. Superior Court held that all residential rental agreements contain an implied warranty of habitability, which means regardless of what your lease says, your landlord has a duty to ensure the unit is livable, safe, and not in need of repair.  A landlord is responsible for repairing all serious defects that affect a rental unit’s habitability.  In addition, the landlord is responsible for any significant failures to comply with state and local building and health codes. 
What are a tenant’s responsibilities regarding repairs?
Under the implied warranty of habitability, a landlord is not responsible for damages caused by a tenant or a tenant’s guest, family, or pets. Tenants are legally required to maintain their rental units, including common areas such as hallways. The law specifies that tenants are responsible for any damage that results from their neglect or abuse. A tenant may be required to pay for repairs caused by the tenant or the tenant’s family, pets, or guests. 
What are some techniques that a tenant may legally use to compel a landlord to make repairs?
If a rental unit has significant habitability issues that directly affect a tenant’s health or safety and the landlord does not make repairs without good reason, the tenant has the following remedies:
- The tenant may undertake the repairs or pay to have them done and then deduct the cost, up to the amount of one month’s rent.  This is referred to as the “repair and deduct” remedy.
- The tenant may voluntarily abandon the unit or threaten to abandon if repairs are not made. This is referred to as the “abandonment” remedy.
- The tenant may withhold rent until the repairs are completed. A tenant is legally able to stop paying some or all of the rent if the landlord refuses to fix defects that compromise habitability of the rental unit. This is called the “rent withholding” remedy.
In each of these cases, the tenant is legally obligated to give the landlord notice of intent. The law specifies that the tenant must give this notice either orally or in writing. If notice is given by email or fax, it is important to follow up with a written letter. The tenant should sign and date the letter and keep a copy.
Note that employing any of these techniques is extremely risky and generally not recommended as they may lead a landlord to evict. Evictions are difficult and expensive to defend and can be very stressful.
Can a tenant file a petition with the rent-control agency?
Many cities have local rent-control agencies (also known as rent boards) with the power to reduce rent. These agencies allow a tenant to file a petition against a landlord to have rent payments reduced until repair issues are resolved. See San Francisco Rent Board Decrease in Services Petition; City of Oakland Rent Adjustment Program Decrease in Housing Services Petition; and City of Berkeley Rent Stabilization Board Individual Rent Adjustment.
In filing such a petition, the tenant is required to show that the landlord’s failure to timely repair has led to a substantial decrease in services (i.e. a diminution of your use or enjoyment of the rental unit). Examples of substantial decreases in services include no heat, lack of clean water, mold, rodents, significant leaks, non-functioning appliances, etc. It is important to note that rent control agencies only have the power to reduce rent. Before filing such a petition, you will want to make sure you have repair requests in writing that the landlord ignored or did not properly address. The tenant can continue to live in the unit at the reduced rent. If a landlord does not have money to pay a judgment in a lawsuit at Superior Court and does not have property liability insurance, a petition with a local rent control agency may be the only way for a tenant to recover.
How can the local building inspector help?
A tenant may also wish to contact the local department of building inspection. The building inspector can visit and cite the landlord for any defects in need of repair. The building inspector can also force the landlord to make repairs by issuing fines for non-compliance. It’s a good idea for a tenant to be present during any building inspection to point out defects. If the landlord still refuses to make repairs after being cited, a tenant should contact any attorney to discuss pursuing legal action against the landlord.
Under what circumstances may a tenant withhold rent or deduct the cost of repairs from his or her rent?
A tenant may deduct money from the rent, up to the amount of one month’s rent, to pay for repairs. A tenant may also withhold rent in order to compel a landlord to complete necessary repairs. This may include any conditions that affect the tenant’s health and safety and that substantially reduce the habitability of the unit, for example, a leaky roof, a gas leak or no hot running water. You will want to speak to a lawyer before withholding rent because it can lead to an eviction.
Under what circumstances might a tenant choose to abandon an uninhabitable rental unit?
Under certain extreme circumstances, a tenant might choose to move out of an uninhabitable rental unit rather than attempt to have repairs made. If a tenant abandons a rental unit because of serious health and safety concerns, the landlord is not entitled to collect rent. It is likely that the tenant has a lawsuit against the landlord if the conditions reach this level.  A tenant who is considering abandoning a unit is encouraged to speak with a lawyer before giving notice to vacate. A judge or jury may find that the issues were not serious enough to warrant abandonment.
Under what circumstances might a tenant consider filing a lawsuit against their landlord?
Depending on the severity of the repair issues, a tenant may have claims against a landlord that can be litigated in Superior Court. For major, ongoing violations, such as no heat, mold, sewage, rodents, leaks, holes in walls, security lapses, non-working appliances, and electrical and plumbing issues, an attorney may take a case on contingency. When a case is taken on contingency, the client does not pay until money is recovered through a settlement or verdict. Damages in an affirmative lawsuit can include return of rent paid, punitive damages (punishing the landlord), payment for emotional suffering, and damages for physical harm.
 Green v. Superior Court, 10 Cal. 3d 616 (1974)
 Green v. Superior Court, 10 Cal. 3d 616 (1974)
 Green v. Superior Court (1974) 10 Cal.3d 616, 637-638 [111 Cal.Rptr. 704, 718-719].
 Civil Code §§ 1929 & 1941.2
 Civil Code § 1942
 Civil Code § 1942(a)
 Civil Code § 1942.