Accessory Dwelling Unit Inspection

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Accessory dwelling units must be inspected by a land use planner prior to final occupancy approval. The ADU inspection is separate from other inspections that you may have.

The information below is not intended to address every code requirement that may arise with your project. New construction must comply with current, applicable codes (e.g., building, electrical, mechanical, plumbing, energy and indoor air quality codes).

Permits are Required

Any work that is being done to the existing building, plumbing system, electrical system or mechanical system will require a permit from the city. This includes, but is not limited to: new or altered construction of walls, stairs, guardrails, drywall; new or altered plumbing lines, added plumbing fixtures; new or altered electrical circuits or fixtures; and new or altered mechanical work, ducting or appliances.

Code Requirements

Fire-Resistant Separation

Code Reference: International Residential Code (IRC) R302 & R202

Fire separation is not required if all required smoke alarms in the ADU and in the primary residence are interconnected in such a manner that the actuation of any one alarm will activate all other alarms in the ADU and primary residence.


The ADU is required to be separated from the primary residence by not less than one-hour floor and wall assemblies tested per ASTM E 119 or UL 263, with penetrations in accordance with IRC R302.4. Any door separating the dwelling units must be, at minimum, a listed 45-minute fire-rated door equipped with a self-closing device.

Smoke Alarms

Code Reference: IRC R314

A smoke alarm must be located within every sleeping room, outside of and in the immediate vicinity of all sleeping areas and on every level of the building. Combination smoke and carbon monoxide alarms are acceptable.

Carbon Monoxide Alarms

Code Reference: IRC R315

A carbon monoxide alarm must be located outside of and in the immediate vicinity of each sleeping area and on every level of the building. Any sleeping room containing a listed direct-vent fuel-burning appliance must have a carbon monoxide alarm installed within the room.

Room Dimensions

Code Reference: IRC R304 & R305

Habitable rooms, not including kitchens, must have a minimum room area of 70 square feet with a minimum dimension of seven feet in any direction.

Habitable rooms must have a minimum ceiling height of seven feet. Beams, ducts and other obstruction may project to within six feet eight inches in habitable rooms in basements only. Bathrooms and laundry rooms must have a minimum ceiling height of six feet eight inches.

Egress Door

Code Reference: IRC R311.2

The ADU must have an unobstructed path of travel to an exterior door. The door must be side-hinged, with a clear opening width of 32 inches and height of 78 inches. If no path exists to an acceptable door in the primary residence, the ADU must have a separate egress door.

Emergency Escape and Rescue Openings

Code Reference: IRC R310

Basements and all sleeping rooms must have an emergency escape and rescue opening that leads directly to a yard or public way. A door may be used as a rescue opening. Emergency egress windows must provide:

  • Minimum clear openable area of 5.7 square feet, minimum openable height of 24 inches and minimum openable width of 20 inches. (Note: Windows at grade level or below are permitted a minimum clear opening area of 5 square feet)
  • Maximum finished sill height 44 inches above the floor
  • Any bars, grills, or covers must be releasable from the inside without the use of any key, tool, or special knowledge.

Window wells for below-grade egress windows that are deeper than 44 inches are required to have an egress ladder.

Light and Ventilation

Code Reference: IRC R303 & M1507

Habitable rooms must be provided with natural light by glazed openings not less than eight percent of the floor area, or artificial lighting must be provided.

Habitable rooms must be provided with ventilation through openable window areas a minimum of four percent of the floor area, or mechanical ventilation must be provided per IRC section M1507.

Exhaust Fans

Code Reference: IRC M1507.4

Local exhaust fans which are vented to the exterior of the building must be provided in all remodeled or newly constructed laundry areas (min. 50 cfm), bathrooms (min. 50 cfm), and kitchens (min. 100 cfm).

In existing laundry and bath rooms, an openable window is permitted instead of mechanical ventilation.

In existing kitchens, an existing exhaust fan in the room may be used in place of the exhaust fan over the range.

Electrical Panel Access

In case of emergency or a tripped circuit breaker, the main electrical panel must be accessible to the primary residence and ADU.

Unit Size

Code Reference: LUC 20.20.120

The accessory dwelling can be a maximum of 40 percent of the total square footage of the residence. The ADU shall contain not less than 300 square feet and not more than 800 square feet, excluding any garage area. If the ADU is completely located on a single floor, the size may be increased to efficiently use all floor area; discuss options with your land use planner.


Code Reference: LUC 20.20.120

There shall be one off-street parking space provided for the accessory dwelling unit, which is in addition to any off-street spaces required for the primary residence.

Special Hazards

If during the ADU inspection the land use planner observes any possible life or safety hazards, a city inspector may be called to verify the existing conditions. The owner may be required to make necessary corrections prior to the approval of the ADU registration. Such hazards may include, but are not limited to:

  • Safety hazards: guardrails, handrails, stairs, proper lighting, etc.
  • Electrical hazards: wiring, outlets, fixtures, panels, etc.
  • Mechanical hazards: chimneys, venting, circulation, etc.
  • Structural hazards: framing, finishes, damage, dry rot, etc.