Important Rules for Building an ADU in The Inland Empire

ADU Rules in the Inland Empire: Size, Permits, Parking & Setbacks

If you’re thinking about building an ADU (Accessory Dwelling Unit) in the Inland Empire, you’re not alone. With more homeowners looking for flexible housing options, ADUs have become a popular way to create rental income, support multi-generational living, and increase overall property value.

The Inland Empire includes both Riverside County and San Bernardino County, and while California ADU laws set the foundation, individual cities may still have their own requirements.

Below is a simple breakdown of the key ADU construction rules Inland Empire homeowners should know before starting design or permits.

1. CAN YOU BUILD AN ADU ON YOUR PROPERTY?

Most Inland Empire cities allow ADUs on lots with existing single-family or multi-family homes. Many properties in the region have larger lots and detached garages, which can make ADU planning more flexible.

Before moving forward, confirm:

• Your zoning designation

• Any local lot coverage or development standards

• Whether short-term rentals are restricted

ADUs are typically best suited for long-term rental or housing for family members.

2. HOW BIG CAN YOUR ADU BE?

ADU size limits depend on the type of unit you plan to build. Many Inland Empire cities follow California’s statewide maximums.

Typical guidelines include:

• Detached ADUs: Up to 1,200 sq ft

• Attached ADUs: Up to 50% of the primary home (max 1,200 sq ft)

• Junior ADUs (JADUs): Up to 500 sq ft, built within existing space

3. SETBACKS & HEIGHT RESTRICTIONS

Setbacks and height rules affect where your ADU can sit on the lot and what kind of design is possible.

Many ADUs follow:

• Setbacks: Often 4 ft from rear and side property lines

• Height:

  • One-story: commonly around 16 ft

  • Two-story: may be allowed depending on city zoning

Because many Inland Empire neighborhoods have larger lots, homeowners may have more placement options — but each city still has its own development standards.

4. BUILDING CODE & SOLAR REQUIREMENTS

All ADUs must meet California Building Code and Title 24 requirements, including:

• Energy efficiency and insulation

• Ventilation and heating requirements

• Safe plumbing and electrical installation

• Fire safety standards (as required)

Most newly built ADUs in California require solar panels, unless the project qualifies for an exemption.

5. PARKING REQUIREMENTS

Parking rules for ADUs are generally easier than most homeowners expect, thanks to California’s statewide ADU laws.

Parking may not be required if:

• The ADU is under 500 sq ft

• The ADU is near transit

• The project is a garage conversion

• The property qualifies under state exemptions

When parking is required, it’s often one off-street space, and tandem parking is typically allowed.

6. THE ADU PERMITTING PROCESS

ADU permits in Inland Empire cities are reviewed through the local building department. State law requires a timely review once your application is complete.

The process usually includes:

• Plan submission

• Corrections (if needed)

• Permit approval

• Inspections during construction

• Final inspection and sign-off

In most cases, cities must review a complete ADU application within 60 days.

FINAL THOUGHTS

Building an ADU in the Inland Empire can be one of the best ways to add livable space and increase your property’s long-term value. The most important step is understanding your city’s rules early so your design is compliant and your permit process stays on track.