Building an ADU in Vancouver, Washington

What you can build in Vancouver

Vancouver's city ADU page says "Up to two ADUs can be built on a lot." They can be attached, detached, a combination of both, or conversions of existing structures. An ADU must be on the same parent lot as a single-family house, duplex, triplex, fourplex, townhome or rowhome. If you add more than two units, they may still be allowed, but no more than two of them can be ADUs.

You can build ADUs in the Low-Scale Neighborhood (LS) and Medium-Scale Neighborhood (MS) zones. The city says ADUs may also be possible in the Mixed-Use Neighborhood and Regional Activity Center zones, but it is less likely because of their higher density requirements. Look up your zone with the Clark County Property Information Center.

New code. The city's updated Comprehensive Plan, zoning map and zoning code "went into effect on July 31, 2026." The new Title 20 zoning code regulates ADUs through "building types." A house with ADUs uses the Flex-Plex Building Type, a cluster of two to six units on one parent parcel. The copy of Title 20 that the city links from its permits page is dated May 5, 2026, so confirm the current standards for your lot with Land Use Planning. See our Washington ADU law page for the state rules behind these changes. [1][2][4]

Size, height and setbacks

Size. "A dwelling unit must be 1,000 square feet or less to be considered an ADU and qualify for reduced impact fees." A larger unit may still be allowed, but not as an ADU. The ADU can't be smaller than the Washington State Building Code requires.

Flex-Plex standards (the building type for a house with ADUs):

• Side setback from a neighboring lot: at least 5 feet, and buildings on the same lot may share a zero lot line
• Rear setback: at least 5 feet from a neighboring lot, 0 feet from an alley
• Front: buildings on the primary street sit 5 to 20 feet from the lot line
• Open space: at least 10 percent of the lot
• Impervious area: 65 percent of the lot for fewer than three units, 75 percent for four to six

Height. Flex-Plex height follows the zone. In the Low-Scale Neighborhood zone the maximum is "Three (3) floors above the adjacent grade and forty-five (45’) feet."

Building code spacing. A detached ADU must be at least 10 feet from all other structures, including the house, decks, garage and sheds, or meet extra requirements such as sprinklers or 1-hour fire-rated construction. An ADU doesn't have to look subordinate to or match the main house. [1][2]

Parking

"Like all dwelling units, there are no minimum vehicle parking requirements for ADUs." The zoning code's parking table lists "None Required" for any residential use. If you choose to build parking, the code has rules for where it goes and what it's made of; in the Flex-Plex type, parking is reached from a side street or alley if one exists. [1][2]

Fees

Impact fees. Under VMC 20.450.030, impact fees for up to two ADUs of 1,000 square feet or less "shall be 50% of the principal unit." If the main house already exists, the ADU's fee is based on what the house's fee would be if it were built today. The city offers a residential impact fee deferral application on its residential permits page.

Permit fees. You pay plan review fees when your application is entered and the rest of the permit fees when plans are approved. A Request for Utility Services is free and gives an overview of costs to connect new units to water and sewer. A Pre-Application Conference for one to six units on one lot costs $382.

Tax relief. An ADU built as part of an addition or remodel may be eligible for property tax relief for up to three years. You must apply with the Clark County Assessor before construction is finished; see the Homeowner's Remodel Exemption. For budgeting help, see our ADU cost guide. [1][2][3]

Utilities

Some utilities can be shared between the house and one or two ADUs, but each unit needs separate shutoffs and its own temperature control. Ask Clark Public Utilities at 360-992-8558 whether you need a power upgrade or separate meter. If the property is on a septic system, check with Clark County Public Health. Before you apply for an ADU permit, you must submit a Request for Utility Services to find out whether a civil engineering review is needed. [1][3]

Garage and other conversions

The city says an existing garage or other accessory structure "may be converted into an Accessory Dwelling Unit (ADU), provided it can meet applicable zoning, building and safety standards."

Washington law goes further on setbacks: cities must allow ADUs in existing structures, including detached garages, "even if they violate current code requirements for setbacks or lot coverage." If your garage sits closer to the lot line than the code allows, raise this with Land Use Planning.

Attached ADUs need 1-hour fire-rated construction and STC/IIC 45 sound separation. The city makes one exception: a single ADU created entirely inside an existing home may not need that separation if hard-wired interconnected smoke detectors run through the home and ADU. In that case the converted space needs a finished ceiling at least 6 feet 8 inches high and legal egress windows. Multiple ADUs, detached ADUs and ADU additions need full fire and sound separation. See our garage conversion guide. [1][5]

Renting or selling it

You don't have to live on the property to have an ADU. You can live in it, rent it, or sell it; the city says ADUs "can be sold as individual units." Selling one separately may involve a land division, so ask Land Use Planning what your lot would need. Long-term rentals must be registered and periodically inspected.

A short-term rental (fewer than 30 consecutive nights) needs a city permit, a state and city business license, liability insurance and a notice letter to your neighbors. The application fee is $265. The city may issue no more than 870 active short-term rental permits at a time, first come, first served, and permits expire when the property changes hands. Short-term rentals can't operate in an accessory structure that isn't a legal dwelling unit. [1][2][6]

Permit steps in Vancouver

1. Check your zone and property

   Look up your property and zoning on the Clark County Property Information Center or the city's Property Information Lookup. [1]

2. Request utility services (required, free)

   Submit a Request for Utility Services before applying, unless you had a Pre-Application Conference in the last 365 days. It shows water and sewer availability and costs, and whether you need a civil engineering (ENG) permit. Questions: Permit Center Engineering, 360-487-7804. [1][3]

3. Get advice if you want it

   Book a free 30-minute virtual appointment with Permit Center staff, or pay $382 for a Pre-Application Conference with a written staff report. Both are explained on the Residential Building Permits page. [3]

4. Apply for a Residential Building Permit (RES)

   Use the New Housing or Dwelling Unit, including ADU, application and submittal checklist. Email the completed form to eplans@cityofvancouver.us, pay plan review fees, then upload plans in ePlans. [3]

5. Answer review comments

   Reviewers check planning and zoning, structural and fire requirements. If they need changes, you'll get an email and respond in ePlans. [3]

6. Pay fees and get your permit

   When all reviews are approved, pay the final fee total, including impact fees. Then download the approved plans, permit and inspection card from ePlans. [2][3]

7. Build and schedule inspections

   Keep the approved plans and inspection card on site and schedule inspections as you build. Inspectors post results online. [3]

Who to call

• Building Plans Examiners

  ADU building code and plan review questions

  360-487-7828

  City Hall, 415 W. 6th St., Vancouver, WA 98660

  [1]

• Land Use Planning

  Zoning, building types and setbacks

  360-487-7803

  [1]

• Permit Center Engineering

  Request for Utility Services and civil engineering review

  360-487-7804

  [3]

• Clark Public Utilities

  Electrical service, meters and power line clearances

  360-992-8558

  [3]

Questions people ask