Bringing UDUs to Light: Ordinances 240803 / 250798

San Francisco has long had thousands of “in‑law” or basement units that were built or used without permits (Unauthorized Dwelling Units, or UDUs). Too often, owners, contractors, and even insiders tried to hide these units, undercount them on plans, or quietly remove them, sometimes backed by bribery or “special treatment” in the permit process. This new ordinance is meant to formalize how UDUs are handled, make unit counts honest, protect existing housing, and cut down on back‑channel deals, fraud, and workarounds.

Is this relevant for you right now?

This ordinance went into effect on October 5, 2025. However, you are mostly in the clear (for now!) if all of these are true:

• You are not filing a Development Application with the Planning Department.

• You are not pulling building permits that change the UDU area (kitchen, bath, doors, layout, stairs, windows).

• There is no open complaint, violation, or inspection related to the unit.

  
  

In that “do nothing, change nothing, no permits” scenario, the City’s new disclosure and investigation rules usually won’t get triggered.

What triggers the ordinance for you

You need to start paying attention to UDU rules if any of the following happens:

• You file a Development Application (major project, additions, or changes to unit count). The City now requires you to disclose any UDUs and Planning must look for them, verify unit counts, and inspect before approving any loss of units.

• You apply for building permits that touch the UDU space in a “unit‑like” way, such as removing or adding a full kitchen or wet bar, a full bathroom, doors that create or remove a separate unit, or interior stairs that connect previously separate spaces.

  • These permits often trigger a UDU screening and can be treated as removal of an unauthorized unit under Planning Code Section 317.

• You submit PLANS for other interior improvements. This legislation is intended to “catch” you if you misrepresent the property configuration in the plans. If you’re replacing a heater, or doing a basic unit renovation to another unit, you won’t need plans, but any work that requires showing the building at large in the drawings will require that you honestly represent and admit there is an illegal unit in the building.

• There is enforcement: a neighbor or tenant complains, a fire or safety inspection happens, or DBI/Planning opens a violation on the unit.

If it is triggered: What steps to take

If the city gets wise to the fact that you have an illegal unit, assume you must deal with the UDU directly. In plain terms:

• Step 1 – Acknowledge the unit

  • Treat the UDU as real housing in your plans and forms: show it on drawings and list it in the unit count.

  • Do not try to “forget” it; misrepresenting units is exactly what this law is meant to stop.

• Step 2 – Ask: legalize or remove?

  • The City’s starting point is: try to legalize the UDU if reasonably possible, using the Dwelling Unit Legalization / ADU programs.

  • If it truly cannot be legalized (for code, safety, or zoning reasons), then you can apply to remove it. Fair warning though, this is a VERY high bar and requires a conditional use hearing at the Planning Commission. Almost none of the applications to remove a unit are approved due to the current housing crisis.

• Step 3 – Follow the formal path

  • Work with a design professional to evaluate whether legalization is feasible and at what cost, and prepare accurate plans and applications.

You can expect planning to screen for UDUs, investigate unit counts, and inspect before approving any loss of a residential or unauthorized unit. DBI will also be applying stricter oversight to catch fraud, bribery, or incomplete disclosures around UDUs and unit counts.

In short: if you’re just sitting tight and not touching permits, this mostly sits in the background. The moment you seek approvals or get pulled into enforcement, you must bring the UDU into the light and either move toward legalization or go through a formal, reviewable process to remove it.

Having said all that - illegal units have no legal value. You are at risk if you have a tenant occupying one of these units because they can simply stop paying rent. In fact, they can even demand their previous rental payments be returned to them. If you do have an illegal unit, we strongly recommend you pursue legalization. Speak to an expert, though. Our team of architects are well-versed in these projects and happy to help you!

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