Unwarranted Units in San Francisco: Buying, Legalizing or Removing
An unwarranted unit is living space, often a ground-floor in-law apartment, that has been used as a separate home without the permits that would make it a legal dwelling unit. You can buy a San Francisco home that has one, but you inherit the permit problem: a tenant living there is still covered by the Rent Ordinance, and since 2016 removing the unit has generally required Conditional Use authorization from the Planning Commission (confirm the current rule with SF Planning). The city’s Unit Legalization program, in place since May 2014, lets an owner legalize one such unit per lot if it existed before January 1, 2013.
City planners have estimated that San Francisco has 30,000 to 50,000 unauthorized units, so many buyers will run into one, often on the ground floor of a house built over a garage. This guide explains how to spot one, the three ways an owner can deal with it, and what each choice means for price, tenants and taxes. For the citywide picture, start with our San Francisco real estate guide.
What counts as an unwarranted unit
The city’s term is “unauthorized unit”: one or more rooms in a building used, without a permit, as a separate living or sleeping space independent of the building’s other residential units. Agents and owners also call these in-law units, illegal units or unwarranted units. A finished ground floor with a bedroom and a bathroom isn’t automatically one; what matters is whether it is used, or set up to be used, as a separate home.
How to find out what is legal
Start with the Report of Residential Building Record, or 3R report. The seller is legally required to give it to the buyer, and it shows the building’s authorized use and building permit history. It doesn’t list plumbing or electrical permits.
The city’s current fee is $286 per residential building, plus a 2.5% surcharge for online card payment, and processing takes seven to ten business days. Our list of San Francisco seller requirements covers ordering it.
Compare the 3R with what is actually there. If the report shows a single-family dwelling and you are standing in a second kitchen, you have found the issue. Our property evidence checklist helps organize permits, plans and photos, and the Sunset lower-level space workbook applies the same approach to a typical Sunset ground floor.
Three paths for an unwarranted unit
An owner has three basic choices. Each has a different cost and a different effect on the tenant, the city record and the next sale.
| Path | What it involves | Main trade-off |
|---|---|---|
| Leave it as is | No permits; the space keeps its current use | Enforcement risk remains. A tenant is still protected, and the space can’t be marketed as a legal unit |
| Legalize it | Through the city’s Unit Legalization program or, for some units, state ADU rules | Construction cost and time; a legalized unit stays under rent control if the building was, and can’t be sold separately |
| Remove it | Convert the space back to part of the main home | Under the rules in place since 2016, generally Conditional Use authorization and a Planning Commission hearing, plus compliance with tenant law; confirm the current Section 317 requirements |
The Unit Legalization program
The Board of Supervisors created the program with Ordinance 43-14, effective in May 2014. It added Planning Code section 207.3 and Building Code section 106A.3.1.3, and allows one unauthorized unit per lot to be legalized even where the lot is already at its density limit.
Who qualifies
- One unit per lot. Only one unit on a lot can be legalized through the program.
- The unit existed before January 1, 2013. Direct proof includes a signed lease, rent deposits or eviction records; indirect proof can combine voter rolls, utility bills, letters from former occupants and earlier city enforcement cases.
- No disqualifying evictions. SF Planning says a unit is ineligible if an owner move-in eviction was filed after March 13, 2014 and the notice was served within five years before the permit application, or if another no-fault eviction filed after that date was noticed within ten years.
- Life safety met. The Department of Building Inspection (DBI) decides eligibility, and all life-safety conditions must be satisfied.
What the program waives and what it doesn’t
SF Planning’s current FAQ says the unit must meet the Planning Code except for density, rear yard, open space, exposure for light and air, and parking. Legalization can’t create or worsen a nonconformity for the building’s other legal units. Building and Housing Code standards still apply, which is where the cost usually is: ceiling height, egress, fire separation, light and ventilation.
The steps
- Confirm eligibility, including eviction history, which the Rent Board can provide.
- Hire a licensed architect, engineer or contractor to complete and stamp the city’s screening form and estimate the cost of code corrections.
- Gather floor plans of the whole building, a site plan and proof the unit existed before 2013.
- Submit the screening packet and attend the free screening meeting with the Unit Legalization team.
- File the Planning project application and obtain Planning approval.
- Apply to DBI for the building permit, using the program’s permit fee waivers, and complete the work and inspections.
If the city has already issued a Notice of Violation for the unit, it can be suspended for a year while you legalize. The city’s 2019 community stabilization research put the average cost of bringing a unit to code at about $60,000, based on DBI permit data; treat that as dated, and get a current estimate for the specific space.
Rent control and tenants in an unwarranted unit
The Rent Board is direct about this: a rental unit under the Rent Ordinance means a residential dwelling unit “regardless of zoning or legal status.” A tenant in an unpermitted unit is protected by the ordinance, including its eviction rules, even though the unit is illegal.
Legalizing doesn’t change that. A unit that was subject to rent control stays subject to it after legalization, and the city says the cost of the legalization work can’t be passed through to tenants. Legalized units also can’t be subdivided and sold separately, so legalization is not a route to a condo; see our San Francisco condo guide for how condo status actually works.
Removing a unit is a just cause for eviction under the Rent Ordinance, but the Rent Board says the landlord must first obtain all permits needed to remove the unit before serving notice, and the notice must meet both city and state requirements. If a building is tenant-occupied, involve a tenant-law attorney before you sign a contract, and read our guide to selling a tenant-occupied home.
Removing an unauthorized unit: Planning Code section 317
Under Ordinance 33-16, which took effect on April 10, 2016, Planning Code section 317 required Conditional Use authorization for the loss of an unauthorized unit, by demolition, conversion or merger, in zoning districts where residential use is allowed. The rule applies to building permits issued on or after March 1, 2016.
- The exception. DBI can exempt a unit from the Conditional Use process if its screening finds the unit can’t be legalized under the Building Code.
- What the Commission weighs. Whether the cost to legalize is reasonable compared with the average cost, whether legalization is financially feasible, meaning the value it adds equals or exceeds its cost, and whether it would cause the owner financial hardship if city funds aren’t available.
- Enforcement. When DBI issues a Notice of Violation, the owner must file to legalize the unit unless the Commission approves its removal, and has one year to abate.
These are the rules as SF Planning summarized them in 2016. We could not check them against the current text of Section 317 for this review, and the city’s rules on unit loss have been revised repeatedly, so treat them as background, not as the current rule. Confirm the current requirements with SF Planning, and have a land-use attorney review them, before you plan around removal.
One current point is confirmed: SF Planning’s May 2026 program FAQ says a legalized unit can be merged with an original unit only through the Conditional Use process, with a Planning Commission hearing.
State ADU law and older unpermitted units
California Government Code section 66332 limits when a city can deny a permit to legalize an unpermitted accessory dwelling unit built before January 1, 2020. The city generally can’t deny it for violating building standards or ADU rules unless correcting the violation is needed to meet the substandard-housing standards in Health and Safety Code section 17920.3. Applicants generally don’t pay impact fees or connection charges, and the owner can get a confidential inspection from a licensed contractor before applying.
Whether a particular San Francisco space fits the state rule or the city program depends on how it was built and used. Our guide to unpermitted ADUs in California explains the state side, and an architect who handles city ADU and legalization permits can tell you which route fits.
Buying a home with an unwarranted unit
- Read the 3R report and permit history against the floor plan and what you see on site.
- Ask who lives there and on what terms. Get any lease, rent records and notices, and ask the Rent Board about eviction history if you might legalize.
- Get a contractor’s or architect’s opinion on whether the space can meet code and what that would cost, before you remove your inspection contingency.
- Ask your lender and appraiser how they will treat the space and any rent from it.
- Price the decision you will actually make. Legalizing costs money and keeps rent control; removing may need a hearing; leaving it carries risk.
- Plan for property tax. The city notes that legalization brings an updated assessed value, which can raise the tax bill.
Our guide to buying a home in San Francisco covers offers and contingencies, and investors looking at small buildings should also read our San Francisco multifamily guide. Diamond may refer you to partners we work with; you’re free to choose any provider.
Selling a home with an unwarranted unit
Describe the space accurately. Don’t market a permitted single-family home as a two-unit building, and disclose what you know about how the space was built and used. Our guide to California seller disclosures lists the forms involved.
Decide early whether to legalize, remove or sell as is. Legalizing before listing can widen the buyer pool but takes months and money; selling as is with clear documents, a contractor’s estimate and tenancy records lets a buyer price the decision. Our guide to selling a home in San Francisco covers timing and preparation.
Questions people ask
Is it illegal to buy a house with an unwarranted unit in San Francisco?
No. The sale itself is legal. What you buy is the permit problem and any tenancy, so you take on the decision to legalize, remove or leave the space, along with the enforcement risk.
Can I evict a tenant from an illegal in-law unit?
Only for a just cause under the Rent Ordinance, which covers units regardless of legal status. Removing the unit is a just cause, but the Rent Board says you must first get all permits needed to remove it, and removal itself has generally required Conditional Use authorization since 2016; confirm the current rule with SF Planning. Talk to a tenant-law attorney first.
Is a legalized in-law unit rent controlled?
If the building was subject to rent control, the legalized unit stays subject to it, and the cost of the legalization work can’t be passed through to tenants.
How long does legalization take?
The city doesn’t publish an overall timeline. You need a screening meeting, Planning approval and a DBI building permit, plus construction and inspections, so plan for months rather than weeks.
Can I legalize more than one unit?
Not through the Unit Legalization program, which allows one unit per lot. Other options, such as the city’s ADU program, may apply; ask SF Planning about the specific property.
Does the 3R report tell me if a unit is legal?
It shows the building’s authorized use and permit history, which is the starting point. It doesn’t list plumbing or electrical permits, so compare it with the full permit record and the space itself.
Talk through a property with us
If you are buying or selling a San Francisco home with an in-law space, we can help you gather the 3R report, permit history and tenancy records and line up the right professionals before you commit. This is general information, not legal advice; talk to a San Francisco real estate or tenant-law attorney about your situation. Contact us to discuss a specific address.
Sources & notes
- City and County of San Francisco: Check the feasibility of legalizing an illegal unit in your home
- SF Planning: Dwelling Unit Legalization Program FAQ (updated May 10, 2026)
- SF Planning: Code summary, Ordinance 43-14, legalization of unauthorized units (Board File 131148)
- SF Planning: Code summary, Ordinances 33-16 and 23-16, unit removal under Section 317 (Board Files 160115 and 150494)
- SF Planning: Community Stabilization Strategy, stemming the loss of unauthorized units
- San Francisco Rent Board: Topic 253, renting an illegal unit
- City and County of San Francisco: Request a 3R report
- California Public Law: Government Code section 66332 (unpermitted ADUs built before 2020)
Last reviewed October 2026 by Matthew Martinez.
