Accessory Dwelling Units (ADUs) are no longer just for single-family homes. In California, recent legislation has opened up major opportunities for multifamily property owners to add ADUs—and even Junior ADUs (JADUs)—to increase rental income and address housing shortages.

But just how many ADUs can you legally build on a multifamily lot?

Let’s break it all down, from state law to local interpretations, with bonus guidance on how to get your ADU permits in Palm Springs, Roseville, and other popular areas.

California State Law: ADU Limits for Multifamily Properties

Under California’s AB 68 and AB 881, multifamily properties (e.g., duplexes, triplexes, fourplexes, and apartment complexes) are allowed to add multiple ADUs.

✅ General Rules:

• Up to 2 Detached ADUs allowed on any multifamily lot

• At least one ADU conversion allowed per every four existing dwelling units (within the primary structure)

• Converted ADUs can be built from spaces like:

  • Storage rooms

  • Boiler rooms

  • Basements

  • Laundry rooms

  • Attached garages

• 3 internal conversion ADUs (12 ÷ 4 = 3)

• 2 detached ADUs
  → Total: 5 ADUs

Size Limits for Multifamily ADUs

Detached ADUs:

• Max size: Up to 1,200 sq ft

• Must follow local setbacks and height limits (generally 16 ft to 25 ft)

Converted ADUs:

• No fixed square footage limit from the state, but must meet code and habitable space requirements

Parking & Fire Access Requirements

• No additional parking required for ADUs within ½ mile of public transit

• Detached ADUs typically must meet fire department access rules (e.g., driveway width, turnaround space)

• Open space and lot coverage limits may still apply depending on your city

Construction & Building Codes

• ADUs must be built to California Building Code (CBC)

• Conversions must include full kitchen, bathroom, insulation, and separate HVAC if detached

• Fire separations and sprinkler systems may be required based on local fire codes and existing building type

How to Get an ADU Permit in Palm Springs

Palm Springs offers strong support for ADUs as part of its affordable housing strategy.

Steps:

1. Site Evaluation – Determine eligibility based on zoning

2. Preliminary Plans – Prepare drawings showing unit layout

3. Planning Review – Submit for zoning compliance

4. Building Permit Application – After zoning approval

5. Construction & Inspection

📞 Tip: Work with Accessory Dwelling Unit Builders in Palm Springs, CA who understand local solar requirements and desert code compliance.

How to Get an ADU Permit in Roseville

Roseville ADU permits go through the City’s Planning and Building Division.

Process Includes:

• Site plan, architectural drawings, elevation views

• Energy calculations (Title 24)

• Fire department approval for access

• School and development impact fees (may be waived for small units)

💡 Pro Tip: Ask about streamlined ADU review, which Roseville applies to encourage housing growth.

Top ADU Permit Builders (Regional)

Top ADU Permit Builders in Roseville

• Sierra ADU Solutions

• Roseville SmartHomes

• Golden State Modular

Top ADU Permit Builders in Fremont

• Bay Modular Homes

• NorCal Design & Build

• Fremont Urban Living Solutions

Top ADU Permit Builders in Palm Springs

• Palm Springs Tiny Home Co.

• Accessory Dwelling Unit Builders Palm Springs, CA

• Desert Dream Dwellings

Top ADU Permit Builders in Riverside

• Riverside ADU Creations

• Inland Empire Prefab Solutions

• Summit Ridge Contractors