Building an ADU in Coeur d'Alene

What you can build here

The city says ADUs have been allowed in Coeur d'Alene since 2007, and the ADU code was updated in 2019 and 2021. The rules are in City Code Sections 17.06.650 to 17.06.670. "Accessory dwelling units are permitted within all Residential and Commercial Zoning Districts," and one ADU is allowed "as subordinate to an existing single-family dwelling."

The ADU "may be added to or included within the principal unit, including a basement, or located in a detached structure." The total number of people living in the house and the ADU together can't exceed the code's maximum for a "family." The ADU can't be subdivided or owned separately from the main home. [1][6]

Size, height and setbacks

Size. The code sets "No minimum size." The "Maximum size shall be eight hundred (800) square feet (finished area; does not include unfinished basements)," and an ADU "shall not exceed seventy five percent (75%) of the total square footage of the primary dwelling unit, excluding the garage area."

Height. 32 feet when built within the building envelope of the main house; 18 feet for a one-story ADU in the rear yard; 24 feet for an ADU over a detached garage in the rear yard, which must meet the second-story step back. Railings, parapets and equipment count toward the height.

Setbacks. Inside the main building envelope, an ADU follows the main home's yards: 20 feet in front, 5 feet on an interior side (with at least one 10-foot side yard if there's no alley), 10 feet on a street side and 25 feet in the rear. In the rear 25 feet of the lot, an ADU must be at least 5 feet from the side and rear lot lines, or 3 feet from the rear line on a lot with an alley.

Second-story step back. In the rear yard, the upper floor must step back starting at 10 feet high on an interior side lot line and 15 feet on the rear lot line, at a 45-degree angle. Eaves may project 2 feet into the step-back space.

Pervious surface and design. A lot with an ADU must be at least 30% pervious (grass, pavers, gravel and similar). An attached ADU gets only one entrance on each front or street side, and additions must match the house's roof pitch, siding and windows. [1][2]

Parking

The code says "One additional parking space beyond that required for the principal dwelling is required for an ADU." The city's ADU application asks you to show "One space for ADU" and "Two spaces for primary dwelling unit" on your site plan, each 9 by 20 feet.

Idaho's new ADU law requires covered cities, by February 1, 2027, to stop requiring off-street or guest parking for an ADU unless the main home has no off-street parking, the street isn't paved and built for on-street parking, or the home is within a quarter mile of transit, an employment area or commercial services. City staff wrote that the statute's wording on this point is "a drafting error" that the Legislature "may correct" in January. City staff asked the Planning and Zoning Commission in October 2026 whether to keep a parking stall where the state law allows one or drop the ADU parking requirement entirely. Until the code changes, ask the Planning Department what it will require. [1][2][4][5]

Idaho's 2026 law and Coeur d'Alene's rules

Idaho Code 67-6541 (SB 1354) took effect July 1, 2026 and applies "only to cities with a population greater than ten thousand (10,000)." Coeur d'Alene had 54,628 people in the 2020 Census. By February 1, 2027, the city must amend its rules for land zoned for single-family homes (historic districts and historic properties are excepted) to, among other things, stop limiting an ADU to "less than one thousand (1000) square feet or seventy-five percent (75%) of the size of the primary dwelling," stop requiring owner occupancy, stop setting a height limit lower than the existing house, and stop applying stricter setback, lot size or coverage rules to ADUs than to single-family homes in the same zone. ADUs that meet the rules must be approved administratively, as a matter of right.

Several current city rules conflict with those requirements:

• Size. The city's 800-square-foot cap is below 1,000 square feet. City staff cite a July 29, 2026 Legislative Services Office opinion that a city "may not cap an ADU at 75% of the primary dwelling if that would be smaller than 1,000 square feet."
• Height. State law bars a height limit lower than the existing house, and the city's 18-foot limit for a one-story rear-yard ADU can be lower than that. Staff list "Height of ADU to match existing dwelling unit" as a topic still under discussion.
• Coverage and step backs. Staff say coverage and pervious rules "cannot be stricter for an ADU than for the primary dwelling" and that "The second-story step back must be removed or replaced."
• Owner occupancy. Staff say the rule only applies to short-term rentals "AND WILL BE REMOVED."
• Fees. Staff list "Fees must match the single-family schedule" as already in compliance.

In their report for the Planning and Zoning Commission's October 13, 2026 workshop, staff said they will bring forward code amendments and schedule public hearings to meet the February 1, 2027 deadline. Until then, the city code still says what it says: ask the Planning Department which rule it will apply to your application. See our Idaho ADU law page. [1][4][5][7][8]

Fees

The Planning Department's fee list shows an ADU fee of $150.00, and the ADU application lists a "Review Fee: $150.00." Building permit fees "are based on project valuation"; call the Building Department at 208-769-2267 for details. City staff say the city already meets the state rule that ADU impact and utility connection fees can't be higher than those for other single-family homes. See our ADU cost guide. [2][3][4][5]

Garage and shed conversions

"Any existing detached structure may be converted into an accessory dwelling unit" if it meets the current building code so a permit can be issued, isn't over the property line or in the city right-of-way, and meets current standards if it's expanded outward or upward. An existing garage with a valid building permit and a height between 18 and 25 feet may be converted if it meets the building code requirement. See our garage conversion guide. [1]

Renting it out and short-term rentals

The city's ADU code is written to let homeowners earn "rental income" from tenants in either the ADU or the main home. Before July 1, 2026, the city required a short-term rental permit ($285 the first year, $180 to renew, under its fee schedule) and required a majority owner or an immediate family member to live in the house or the ADU more than six months a year when one of them was a short-term rental.

House Bill 583 changed Idaho Code 67-6539 effective July 1, 2026. It says "No county or city shall require a license, fee, permit, certification, or registration to operate a short-term rental," and it bars "Requiring owner occupation for any amount of time" and other special rules that don't apply to ordinary homes. A city may still require smoke alarms in sleeping areas, a fire extinguisher and carbon monoxide detector on each floor, escape ladders for upper-floor sleeping areas, building-code occupancy limits and an information handout for guests.

City staff wrote on October 13, 2026 that since HB 583 took effect "the City has not been enforcing the STR regulations" and that amendments will remove the permit and the owner-occupancy rule for ADU properties. The city code text and fee schedule still list the old rules until they're amended, so ask the Planning Department at 208-769-2274 what applies. [1][5][9][10][11][12]

Free ADU plans

The city's ADU page links four free ADU plan sets sponsored by Housing Solutions Partnership. The city says they "have been reviewed by building department heads and planners from local municipalities" and are "FREE for use in Kootenai County, Idaho." Your project still needs the city's ADU review and a building permit. See our prefab ADU guide. [2][6]

Permit steps in Coeur d'Alene

1. Check your zone and lot

   Confirm your zoning district on the city's zoning map and district information sheets and compare your lot with the ADU size, height, setback, parking and pervious surface rules. [1][2]

2. Prepare your plans

   You need a site plan showing all property boundaries, setbacks, parking and the main house; floor plans and elevations of all sides; second-story step back elevations for the side and rear yards; and a lot coverage plan with pervious surface calculations. [2]

3. Submit the ADU application with your building permit

   Fill out the city's ADU application, which goes in with the building permit, and pay the $150 review fee. [2][3]

4. Record the notice to title

   Sign the city's Agreement and Notice to Title before a notary and record it with Kootenai County. It runs with the land, states that an ADU is on the property, and commits you to tell buyers about the ADU rules. [1][2]

5. Apply for the building permit

   Building permits are handled through the city's Building.CdaId.org site. Call 208-769-2267 to set up the account it requires. [13]

6. Build and schedule inspections

   Once the permit is issued, schedule inspections through the same online account. The city may also inspect the ADU, with reasonable notice, for compliance with the ADU rules. [1][13]

Who to call

• City of Coeur d'Alene Planning Department

  ADU rules, ADU applications and zoning (email planningdiv@cdaid.org). Monday to Friday, 8 a.m. to 5 p.m.

  (208) 769-2274

  710 E. Mullan Ave, Coeur d'Alene, ID 83814

  [2][14]

• City of Coeur d'Alene Building Services

  Building permits, fees, online permit accounts and inspections

  (208) 769-2267

  710 E. Mullan Ave, Coeur d'Alene, ID 83814

  [3][13][14]

Questions people ask