ADU rules in Gladstone

A detached backyard ADU is an accessory use allowed outright in both of Gladstone's single-household zones, R-7.2 and R-5, with no hearing and no design review. One ADU per lot is the cap. Detached units get their own height limit of 26 feet (below the 35-foot zone maximum) and must include at least two of five listed architectural details: a covered porch at least five feet deep and wide, a recessed entry at least two feet deep, roof eaves projecting at least 12 inches, horizontal lap siding three to seven inches wide, or window trim at least three inches wide. Ordinance 1544, adopted March 10, 2026, put that objective menu in place of the older requirement that an ADU visually match the primary dwelling. Standard accessory-building setbacks apply: 20-foot front and street side, 15-foot rear, and 7.5-foot side in R-7.2 (five feet for irregularly shaped lots) or five feet in R-5.

Attached, internal and addition-style ADUs are allowed on the same terms as detached ones. The code defines an accessory dwelling unit as a unit that 'may be created as a detached structure or within, or as an addition to, a detached single-household dwelling or accessory structure,' and the size rule expressly contemplates internal conversions by exempting a converted existing basement from the floor-area cap so long as no new floor area is added. The two-of-five design-detail menu and the 26-foot height cap are written to apply only to detached ADUs, so an attached or internal unit is governed by the primary dwelling's own standards.

The floor area of an ADU may not exceed 800 square feet or 75 percent of the primary dwelling's gross square footage, whichever is less, so on a 1,000 square foot house the effective cap is 750 square feet. Converting an existing basement is exempt from the size cap provided no new floor area is added. There is no minimum size: Ordinance 1544 (adopted March 10, 2026, City file TXT-26-01) deleted the former 220-square-foot floor along with the old two-bedroom and one-front-entrance limits, and set the 26-foot height cap for detached ADUs, which staff derived as 75 percent of the zone's 35-foot maximum. The city's Planning FAQ page has not been updated for that ordinance and still advertises the repealed 220-to-800 square foot range.

No owner occupancy is required to build an ADU or to rent one on a long-term lease; ORS 197A.425(1)(b)(B) bars Oregon cities of Gladstone's size from imposing one, and Gladstone's code contains no general requirement. The single exception is short-term use: an ADU used as a vacation rental must have a deed restriction recorded in the Clackamas County Clerk's Office, in a form prescribed by the city, requiring that either the primary dwelling or the ADU be owner-occupied for as long as the ADU is used as a vacation rental. That is not a preempted requirement; ORS 197A.425(2) expressly preserves local authority to require owner occupancy when regulating vacation occupancies as defined in ORS 90.100.

Gladstone requires no off-street parking for an ADU. The parking chapter's Table 1 lists no ADU row, expressly requires none for a residential unit under 750 square feet, and by its own terms applies to developments subject to design review, from which single-household dwellings and their allowed accessory uses are exempt. Staff confirmed the point to Council in March 2026, listing 'Cannot require vehicle or bicycle parking' among the state requirements. The one exception is vacation-rental use: an ADU used as a vacation rental must provide one off-street space in addition to whatever GMC Chapter 17.48 requires for the primary dwelling, which ORS 197A.425(2) permits.

Ministerial. ADUs are listed among the accessory uses 'allowed' in the R-7.2 and R-5 districts, which are themselves reached through uses allowed outright, so there is no conditional use hearing and no Planning Commission review. Design review, Gladstone's discretionary site-and-architecture process, expressly does not apply to 'single-household dwellings, middle housing, and their allowed accessory uses.' In practice the only approval is a building permit, which Gladstone routes through the Clackamas County Building Department; the city's land use application list contains no ADU application type.

Nothing in the code restricts renting an ADU long term, and no owner-occupancy or minimum-lease condition attaches to it. Short-term use is regulated: a 'vacation rental' is defined as a dwelling unit or ADU providing vacation occupancy under ORS 90.100, and an ADU used that way must add one off-street parking space and record a Clackamas County deed restriction keeping one of the two units owner-occupied. Separately, GMC 5.04.055 requires a city business license for short-term rentals, with quarterly transient lodging tax remitted under GMC Chapter 5.70 and no more than one rental party occupying a dwelling unit at a time. An ADU cannot be sold separately from the primary house; the code allows no condominium or lot split for it, and ADUs are prohibited outright on any lot created by a middle housing land division.