Staff outlines state middle-housing lot-division rules and pending changes; commission raises water and infrastructure concerns

Planning staff told the commission on Oct. 8 that state law requires cities to allow middle‑housing lot divisions (MHLDs) for certain housing types and summarized a July 2025 amendment that affects accessory‑dwelling‑unit (ADU) allowances.

Staff explained that Senate Bill 458 (often referenced by staff as SB 458) requires jurisdictions to permit lot divisions that enable individually owned ownership of middle‑housing units — duplexes, triplexes, quadplexes, townhomes and cottage clusters — when the development otherwise meets the state’s middle‑housing construction and land‑use requirements. The presenter noted that SB 458 applies to MHLDs permitted on or after June 30, 2022 and that the resulting lots are not automatically granted additional development rights beyond those allowed by the parent lot; a middle‑housing lot remains bound to the parent‑lot standards unless local rules say otherwise.

Staff also described a July 17, 2025 amendment enacted as House Bill 2138 that allows local governments to decide whether to allow ADUs on lots created through MHLDs; jurisdictions may prohibit or add approval criteria for ADUs on those subdivided lots rather than being required to allow them.

Commissioners pressed staff on implementation details. Commissioner Glantz asked whether criteria that applied when planning documents expected more supply remained applicable for a parcel‑removal application; staff agreed to add clarifying findings. Commissioner Allen raised engineering and water‑supply concerns: he noted Troutdale’s dependence on well water and asked whether hydrologists have been consulted, warning that intensifying development without scrutiny of groundwater recharge and infrastructure capacity could create long‑term problems. Planning staff said infrastructure requirements for MHLDs are part of the county and city permitting processes and that many utility and building requirements (meters, separate sewer connections, etc.) already apply to lots created under MHLD rules; staff also noted that state agencies are still drafting implementation rules for the July 2025 amendment and that more guidance is expected in coming months.

Staff outlined next steps: Troutdale must add MHLD procedures into its development code, then return to Planning Commission with proposed criteria and any local options (for example, whether to allow ADUs on MHLD lots). The commission agreed to a multi‑month staff/commission process to draft code language, hold work sessions and, if needed, return with a formal code amendment and public hearings.

Ending: Staff said the first requirement is to codify the SB 458 MHLD process; decisions on ADUs and local approval criteria will be addressed in subsequent code‑writing and public hearings.