How California Law is Making it Easier to Build an ADU in 2025

In an attempt to address the housing crisis in California, the state legislature has passed a series of laws that make it easier for homeowners to build Accessory Dwelling Units (ADUs) on their properties.

Recent changes to state law have removed many barriers that previously made ADU construction challenging or impossible. Here's how these changes could help you add an ADU to your property.

Pre-Approved Plans Are Coming

Starting in 2025, local agencies will be required to maintain a program of pre-approved ADU plans. This is huge news for homeowners! Instead of starting from scratch, you'll be able to:

• Choose from pre-approved designs posted on your local agency's website.
• Get faster approval when using these plans (within 30 days).
• Potentially save money on architectural fees.
• Have more certainty about what will be approved.

More Generous Height and Size Restrictions

The state has established clear, generous standards for ADU sizes and heights:

• Detached ADUs can now be up to 16 feet tall.
• If you're near major transit or have a multi-story main house, you can build up to 18 feet.
• Attached ADUs can be up to 25 feet tall (or as tall as your main house).
• Local agencies must allow at least an 800-square-foot ADU with 4-foot side and rear setbacks.

Parking Requirements Are Simpler

Good news if you're worried about parking! The law now specifies that:

• You don't need to replace uncovered parking spaces that you remove to build an ADU.
• There are numerous situations where you can't be required to add parking for your ADU.

More Options for Multi-Family Properties

Own a multi-family property? The new laws have something special for you:

• You can build up to eight detached ADUs (as long as it doesn't exceed the number of existing units).
• You don't need to modify your existing building to meet current setback requirements.
• You have more flexibility in where you can place your ADUs

Easier Path to Legalization for Existing Units

If you have an unpermitted ADU built before January 1, 2020, the path to legalization is now clearer:

• Local agencies can't deny your permit just because the ADU doesn't meet current standards.
• You can get a confidential inspection from a licensed contractor before applying.
• You'll receive clear information about what makes a building substandard.
• You won't be penalized for coming forward to legalize your unit.

No More Owner-Occupancy Requirements

A significant change that provides more flexibility: local agencies can no longer require the property owner to live in either the main house or the ADU. This means:

• More rental options for property owners.
• Flexibility to rent both units if needed.
• Easier property management for owners who live elsewhere.

What This Means for You

California's commitment to expanding ADU construction is clear. These changes make it easier than ever to:

• Plan your ADU project with confidence.
• Navigate the approval process more quickly.
• Understand exactly what's allowed.
• Legalize existing units.
• Maximize your property's potential.

Further Reading

For more information on the new laws and how they affect you, check out the California Department of Housing and Community Development website.

And remember to check with your local planning department about specific requirements in your area, as some details may vary by jurisdiction. But with these state-level changes, you'll find fewer obstacles and more support for your ADU project than ever before.