Off-Grid Living in Multnomah County, Oregon

Multnomah County is a strange one to research because it's really two (or six) different rulebooks stitched together. If your land is in unincorporated territory, the county's own zoning code governs you. If it's inside Portland, Gresham, Troutdale, Fairview, or Maywood Park city limits, that city runs its own planning and building department, and the county's rural rules don't apply at all. I'll flag which is which as I go.

Zoning. For unincorporated land, Multnomah County's zoning code (chapter covering rural districts) sets district-specific minimum lot sizes: MUA-20 (Multiple Use Agricultural) needs 20 acres, Rural Residential (RR) needs 5 acres, Rural Center (RC) needs 1 acre, and Multiple Use Forest (MUF) varies. Inside any of the incorporated cities, that city's own zoning code takes over entirely, so if you're eyeing a parcel inside Gresham or Portland, call that city, not the county.

Dwellings, tiny homes, RVs. The county requires manufactured or mobile dwellings on rural land to meet Oregon's building code and mobile-home statutes, sit on a permitted foundation, and hit a minimum floor area. Living full-time in an RV or tiny-house-on-wheels on raw, undeveloped land is not treated as a legitimate standalone residence, at least within Portland's code, which generally requires an existing primary dwelling on the lot first. I could not confirm whether Multnomah County opted into Oregon's SB 1013 program that lets some counties permit RVs as rental dwellings, so ask the county directly if that's your plan.

Building permits. Multnomah County Land Use Planning handles permits and zoning verification in unincorporated areas; incorporated cities issue their own. A building permit sign-off for a rural dwelling requires an approved foundation and, notably, an issued septic authorization.

Septic. Here's the quirk: Portland Permitting & Development handles septic permitting for the entire county, including unincorporated areas and every other city in it, under an intergovernmental agreement with the county and Oregon DEQ. Start with the county's zoning verification, then go to Portland's septic program for the actual permit.

Greywater and rainwater. I found no county-specific ordinances on either. Both appear to default to Oregon's statewide rules, DEQ's tiered greywater permit program and the state's roof-catchment exemption. Not confirmed whether Multnomah layers anything extra on top.

Wells. Oregon Water Resources Department handles well construction and water rights statewide; no distinct county well ordinance turned up. The county's own water-quality program is a resource for drinking-water testing questions.

Off-grid utilities generally. Nothing bans living disconnected from power or municipal water, but you can't get final building-permit sign-off without an approved septic system in place.