Building code regulations for legalizing existing accessory dwelling units

Accessory and junior dwelling units need to comply with State and local building code regulations. These regulations apply to the legalization process for existing dwelling units.

For detailed regulations, refer to:

• Health and Safety Code Section 17920.3
• City Code Chapter 8: Building, Construction and Fire Prevention

Key requirements

These apply to both ADUs and JADUs.

• Insulation, lighting, ventilation, and heating systems need to be adequate.
• The exterior door needs to be a side hinged swinging door. Sliding doors are not allowed. (CRC R311.2)
• Direct access to the electrical panel/disconnect serving the unit, but without requiring access through the main dwelling unit. (CEC 225.35) Bedrooms/sleeping areas require emergency escape windows. (CRC R310.2)
• If there are already 5 bathrooms in the building and a new bathroom is added, you need to verify or upgrade the sewer line to 4” diameter. (CPC Table 703.2 Footnote 4)
• If a gas appliance (like a furnace or water heater) is in a sleeping area or bathroom (CPC sec. 504.1 and CMC sec. 904.1), it needs to be in a closet:
  • With a listed, gasketed door assembly and listed self-closing device, or
  • It’s a direct-vent type
• Openings from a private garage directly into a room used for sleeping purposes is not allowed. (CRC R302.5.1)
• Conversion of an existing garage requires a 10-mil Class A vapor retarder, lapped not less than 6 inches, over the existing garage slab. (CRC R506.2.3)
• If it’s less than 10 feet between the main house and a detached ADU (CRC R302.3), one of the walls (either the house or ADU) needs to be:
  • 1-hour fire rated
  • Opening on that wall needs to be 45-minute fire rated

ADU-specific requirements

• The living room is at least 190 sq ft.
• Includes:
  • Separate closet
  • Kitchen sink
  • Cooking appliance and refrigerator, each with a clear working space of at least 30″ in front, lighting, and ventilation (unless it’s an accessible, adaptable unit)
  • Separate bathroom containing a water closet, lavatory, and bathtub or shower.
• Comply with rent restrictions, including a deed restriction.

Refer to CBC 1208.4 for details about what to include in your ADU.

Fire safety

• 1-hour fire rated wall and floor-ceiling assembly separation from primary dwelling unit.
• Supporting construction of rated floor-ceiling assembly must have the same or greater fire rating.
• Fire-resistance rated floor/ceiling and wall assemblies need to extend to and be tight against the exterior wall.
• Wall assemblies need to extend from the foundation to the underside of the roof sheathing.

Refer to CRC R302.3 for fire safety details.

Heating

• Heating facilities need to be provided.
• They must be separate from the main dwelling unit heating as return air from one dwelling unit shall not discharge into another dwelling unit through the heating or cooling air system.

JADU-specific requirements

Owner occupancy

JADUs are subject to an owner-occupancy requirement. Someone with legal or equitable title to the property must live on the property, in either the main house or the JADU. It must be their primary residence and legal domicile.

Deed restriction

Before you can get a building permit, the City must record a deed restriction with the County Recorder’s office. It will:

• Include the required restrictions and limitations
• Run with the land and bind all future owners, heirs, and assigns