Permitting Illegal ADUs

Do you have an illegal ADU that you'd like to convert into a legal one? This guide will walk you through the different options for bringing a unit up to code.

Last updated 
February 27, 2023
Permitting Illegal ADUs

Guide to Permitting Illegal ADUs

If you live in Los Angeles, you may have heard of the city’s Unpermitted Dwelling Unit (UDU) legalization program that allows owners of illegal ADUs to bring the units up to code. But how does it work, and what does it entail?

In the following blog post, we’ll explain the ins and outs of UDU law and walk you through the different options for bringing an unpermitted accessory dwelling unit up to code.

Options for legalizing unpermitted ADUs

When it comes to legalizing an illegal accessory dwelling unit in Los Angeles, there are two main options: the aforementioned UDU Legalization Program and rebuilding the unit to code.

Read on to learn more about each option.

Option 1: UDU Legalization Program

The Unpermitted Dwelling Units (UDU) Legalization Program applies to illegal dwelling units in the City of Los Angeles. Beginning in May 2017, this voluntary program makes some unpermitted units eligible for legalization, assuming all safety conditions are met.

UDULP Benefits

Some units may qualify for a streamlined legalization process. To take advantage of the streamlined program, applicants must complete a six-step process with City Planning, the Department of Building and Safety (LADBS), and the Housing and Community Investment Department (HCIDLA).

Using the UDULP may require less work and carry a lower price tag than rebuilding the unit. However, this is dependent upon the condition of the unit and how much updating it needs in order to be brought up to code.

UDULP Drawbacks

Because it is an LA City program, it is only applicable to properties located within the City of Los Angeles. And not all LA properties are eligible—in fact, it only applies to properties in multifamily residential districts (i.e. R2 or above). If your property is zoned single-family residential, it will not qualify for the UDU program.

Although the permitting process is streamlined, the UDU legalization program has a number of specific requirements that must be satisfied in order to be eligible. Read the Unpermitted Dwelling Unit (UDU) Ordinance to learn more.

Because the program was designed to create more affordable housing in LA, there is an affordable housing requirement: the newly legalized unit must be designated low- or moderate-income affordable housing. This is not a drawback per se, but it can limit the rental income potential of the unit.

How to Apply for UDULP

More information about the UDU program can be found on LA’s Planning Department website. To apply, email Los Angeles City Planning’s Development Services.

Option 2: Rebuild the unit

In many cases, this is the best or only option available. In this scenario, all existing work is removed, the unit is brought down to the studs, and the project resumes essentially from scratch. It is functionally a conversion ADU—though instead of being converted from a garage or other auxiliary structure, it is converted from an existing ADU (albeit an illegal one).

In some instances, the condition of the structure might be too poor to convert the unit, or the structure itself might not have a permit. When that’s the case, the original unit will need to be demolished and a new unit built in its place. Read our blog post on conversion vs. demolition to learn more.

Rebuilding Benefits

Regardless of the original structure’s condition, the end result is a well-built, legalized dwelling unit.

Unlike the UDU program, this approach is applicable to all unpermitted ADUs, regardless of their jurisdiction or zoning code. There are no affordable housing requirements on the units, which means they can be rented out at market rate.

Because it is essentially a conversion ADU, the specific UDU ordinance requirements do not apply; only state and local ADU law. As such, there is no concern of associated lawsuits or being reported for violations.

Rebuilding the unit from the studs up means that the owner could potentially use the Cal HFA ADU grant to help offset the prebuilding costs, if income requirements are met. Read our blog post on the Cal HFA ADU grant to learn more.

Rebuilding Drawbacks

It can feel disappointing to remove so much of the existing work (and in some cases, completely demolish the unit)—especially when a simpler conversion was expected. Rebuilding a new unit from the studs (or ground) up can also be more expensive than a UDU program conversion project.

Rebuilding Process

First, you’ll need to review existing permits to determine what part of the structure is legal. Only  permitted garages, sheds, or existing structures can be converted to an ADU. If the structure itself is not permitted, it will need to be removed and treated as a new construction ADU. If you don’t have the permit, don’t worry—it might be on file with your local jurisdiction.

Next, a site inspection is needed to review existing site conditions.

If you’re working with Otto, the next step is a design session to create a plan that will meet your functional needs and satisfy the ADU code requirements for spatial layout and utility connections.

Once the plans are agreed upon, we’ll review the plans with a structural engineer and Title 24 consultant before submitting them to the city for approval. Read our blog post on the ADU permitting process to learn more about this step.

During construction, an inspector will determine if existing work can be remediated or needs to be replaced.


Q: Why do I need to redo the electrical or water runs to the illegal ADU?

A: Garages as they were originally built were not intended to be habitable units. There are many code requirements to convert these types of structures to an habitable space. Even if there is already electricity and water in the garage, and that work was permitted, it may not meet the stricter requirements for dwelling units (such as diameter of gas or water lines).

Q: Can I use my existing windows and doors?

A: Potentially. ADUs have a strict energy compliance code to meet (CA’s Title 24). Even if the windows themselves are to code, their installation and/or sealing strategy might not be.

Q: Is there an Owner Occupancy requirement?

A: The 2020 ADU laws waived the owner occupancy requirement through 2025, making ADUs permitted during this time frame exempt. It’s currently unclear what will happen beyond 2025, but if you plan to rent out your main house and ADU in the future, we suggest doing it before 2025.

Remember: in LA City, ADU permits are valid for up to 2 years before you build. Even if you’re not ready to start construction, you can still get the plans and permits ready.

Which option is best?

When it comes to deciding whether to use the UDU program or rebuild the unit, it really depends on the project. Because of the program’s restrictions and requirements, it’s only applicable to a slim percentage of unpermitted units. If your illegal ADU qualifies, it could be a good option for you.

If your unit doesn’t qualify for the program or if converting the unit isn’t feasible, you can’t go wrong with a rebuild. While it might seem defeating at first to undo so much existing work, the  resulting unit will likely be of a higher quality. And although you won’t be able to take advantage of the UDU program’s streamlined process, the general ADU building process is streamlined as well. Additionally, there are a number of local and statewide grants and loan programs available to help offset the cost (as well as financing options if you don’t have enough cash on hand).

And if you choose to rebuild your granny flat, you can hire a trusted full-service ADU company like Otto to create a new unit even better than the original one. Contact Otto for a free consultation and property assessment, and begin designing your beautiful, legal ADU.

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