Multnomah County, OR Building Permits, Zoning & Septic Rules

Multnomah County, Oregon zones most of its unincorporated land itself, but does not issue building permits: the City of Portland's Permitting & Development bureau issues them for some areas of unincorporated Multnomah County under an intergovernmental agreement¹². Portland also administers septic (onsite wastewater) permitting for the entire county under a separate agreement with Multnomah County and Oregon DEQ³. Because which office you deal with depends on exactly where your parcel sits, and not every unincorporated area is Portland-served, confirm your specific jurisdiction before you assume any office covers you⁴.

At a glance

Building permit: Required; issued by Portland Permitting & Development for some unincorporated areas, not by the county itself¹
Zoning: Yes, administered by county Land Use Planning for most unincorporated areas; some pockets use city zoning under agreement⁵
Septic permits: Required countywide, administered by Portland Permitting & Development under an intergovernmental agreement³
Owner-builder: Available statewide if you build entirely with your own or unpaid help and haven't used it in the last 5 years⁶⁷
Minimum lot size (rural zones): 80 acres in Exclusive Farm Use, 20 acres in Multiple Use Agriculture, 5 acres in Rural Residential⁸⁹¹⁰
RV living: A county may allow one RV as a rental home on qualifying rural residential property; campground/park stays cap at 90 days¹¹¹²
Manufactured homes: Allowed on private land with the owner's consent statewide; mobile-home-park units need at least 800 sq ft in some zones¹³¹⁴
Accessory dwelling units: One ADU per detached home required as of right; unincorporated county ADUs can't be short-term rented¹⁵¹⁶

Who to call

Building permits

Portland Permitting & Development

Building permits for some areas of unincorporated Multnomah County, under an intergovernmental agreement with the county

503-823-7300

Planning & zoning

Multnomah County Land Use Planning

Zoning and land-use review for most of unincorporated Multnomah County

503-988-3043

[email protected]

Septic permits

Portland Permitting & Development - Septic Permits

Septic (onsite wastewater) permits and inspections for all of Multnomah County under an intergovernmental agreement

503-823-6892

[email protected]

Roads & driveways

Multnomah County Transportation Division

Driveway (road right-of-way access) permits for unincorporated Multnomah County roads

503-823-4000

Contact details are copied from each office’s official page and were checked against it on September 28, 2026.

Do you need a building permit in unincorporated Multnomah County, Oregon?

Yes, a building permit is required statewide in Oregon for constructing, enlarging, altering, repairing or moving a residential building or structure, and that includes unincorporated Multnomah County¹⁷. Multnomah County itself does not issue that permit: the City of Portland's Permitting & Development bureau issues building permits for some areas of unincorporated Multnomah County, while the county's own Land Use Planning division handles the zoning review that goes alongside it²¹. That word 'some' matters: not every unincorporated parcel is Portland-served, and other unincorporated pockets are administered by neighboring cities under separate intergovernmental agreements, so confirm which office covers your specific parcel before you assume Portland is it¹⁸. Oregon's own residential construction code, the Oregon Residential Specialty Code, applies statewide to one- and two-family dwellings and townhouses, with its construction provisions mandatory since April 1, 2024¹⁹. One narrow exemption exists even without a Portland or county building-permit desk: certain detached, nonhabitable, one-story accessory structures under 200 square feet and under 15 feet of average roof height don't need a building permit, though they may still need electrical, mechanical or plumbing permits¹⁷.

Who issues building permits and zoning approvals in Multnomah County, and how do you reach them?

For the building permit itself, contact Portland Permitting & Development's general inquiries line at 503-823-7300 if your parcel is in one of the unincorporated areas the city serves²⁰. For zoning, contact Multnomah County Land Use Planning directly at 503-988-3043 or [email protected]; that office administers zoning for most of the county's unincorporated land and can tell you what your specific parcel is zoned⁴. Multnomah County is explicit that it does not issue building permits itself, so a call that starts at the county for a permit question gets routed to whichever city serves that address¹. The county land-use fee schedule effective July 1, 2026 lists a $527 zoning plan check and a $1,620 floodplain development permit, although other application fees, deposits or notice charges can apply²¹. Because zoning and building-permit authority run through two different offices here, and building-permit coverage varies by exact location, start with Land Use Planning to confirm jurisdiction, then follow their referral to the correct permitting office⁴.

Does Multnomah County have zoning?

Yes: Multnomah County is responsible for zoning in most of its unincorporated areas, administered through the county zoning code, though some unincorporated pockets are administered by neighboring cities instead under intergovernmental agreements⁵²²¹⁸. Minimum lot sizes vary sharply by zone: 80 acres for a new parcel in the Exclusive Farm Use zone, 20 acres in Multiple Use Agriculture (MUA-20), and 5 acres in Rural Residential (RR), each with its own exceptions written into the code⁸⁹¹⁰. In the MUA-20 zone, yard setbacks run 30 feet in front, 10 feet on the side, 30 feet on the street side and 30 feet in the rear, and maximum structure height is 35 feet, though barns, silos and similar structures can exceed that if set back at least 30 feet from any property line²³²⁴. A dwelling in the Multiple Use Forest (MUF) zone built after August 14, 1980 needs at least 600 square feet of floor area and must sit on a permitted foundation²⁵. Statewide, Oregon also sets its own resource-land floors that a county's zoning must respect: at least 80 acres for exclusive farm use land not designated rangeland, 160 acres for exclusive farm use rangeland, and 80 acres for designated forestland, unless the county has an approved smaller acknowledged minimum²⁶.

How do septic permits work in Multnomah County?

Septic (onsite wastewater) permitting for all of Multnomah County, including incorporated cities and unincorporated areas, is administered by the City of Portland under an intergovernmental agreement with the county and Oregon DEQ³²⁷. That makes septic the one process here that genuinely runs countywide through a single office, unlike building permits. Every septic tank permit needs an approved plumbing inspection for the sanitary line before the permit can be finalized, and if the system uses a pump, approved electrical inspections for the underground trenching and the septic panel are required too, with inspection schedules differing east and west of the Willamette River²⁸. Where a municipal sewer isn't available, development must use an onsite wastewater or septic system instead, and the site needs enough usable space, required setbacks, adequate sewage-flow capacity and suitable soil or water-table conditions before DEQ will issue the construction permit²⁹. Only about 1.5% of Multnomah County's mapped soils are free of severe limitations for a conventional septic drain field, so budget for a site evaluation and likely an alternative or engineered system on nearly any parcel³⁰. Reach Portland's septic program at 503-823-6892 or [email protected]³¹.

Can you live in an RV or place a manufactured home on your land in Multnomah County?

Oregon law lets a county allow one recreational vehicle to be sited on a rural lot or parcel as a rental home, but only under specific conditions: the property must be outside an urban reserve, an owner-occupied single-unit home must already be the owner's primary residence there, no other dwelling can be on the property, the RV can't be used for vacation or short-term stays, and the county can require registration and a written rental agreement¹¹. Separately, a recreational vehicle can be occupied year-round in a manufactured dwelling park, mobile home park or RV park if it's lawfully connected to water, electrical and sewage service, or temporarily on a lot with a home made uninhabitable by a disaster, for up to five years³². Outside those specific situations, camping in a county-regulated campground or RV park in the MUA-20, RR, BRC, SRC or RC zones is capped at 90 days in any consecutive 12-month period and is defined as temporary, not residential, occupancy, so it does not answer whether you can simply live in an RV on ordinary unincorporated land¹². A manufactured home is more straightforward: Oregon law lets you occupy one on private land with the landowner's consent if the site has adequate water supply and sewage disposal, and a manufactured home in a mobile-home-park space within certain county residential zones needs at least 800 square feet, built after June 15, 1976, with a state compliance insignia¹³¹⁴.

Building a home in Multnomah County: the steps, in order

Confirm your parcel's exact jurisdiction with Multnomah County Land Use Planning at 503-988-3043, since zoning, building permits and even which city serves you can vary by exact location⁴¹⁸.
Confirm your zoning district's minimum lot size and setbacks; for example, Rural Residential requires 5 acres and Multiple Use Agriculture requires 20 acres for a new parcel⁴¹⁰⁹.
Apply for your building permit through Portland Permitting & Development at 503-823-7300 if your parcel is in a Portland-served unincorporated area; construction must follow the Oregon Residential Specialty Code²⁰¹⁹.
If you are not on public sewer, apply for your septic permit through Portland's onsite program at 503-823-6892; plan for a plumbing inspection on the sanitary line before the permit is final³¹²⁸.
As an owner-builder, you can build your own single-family home and adjacent outbuildings yourself, or with unpaid help from friends and relatives, if you haven't used this exemption in the past five years; a permit is still required, and it must note whether the structure meets the exempted structural requirements⁷.
If your driveway needs a new or altered connection to a county road, apply for a driveway permit through the county; the county says these usually take about three weeks and require a site plan, proof of insurance and, for paving work, a refundable deposit³³³⁴.
Budget time for inspections: work must be inspected before it is covered by drywall, concrete or backfill, and a permit expires if it goes without an approved inspection for more than 180 days³⁵.

What to check before you buy land in Multnomah County

Jurisdiction: because zoning, building permits and septic run through different offices depending on exact location, confirm with Land Use Planning which agencies actually cover your specific parcel before you rely on anything in this guide⁴. Soils: only about 1.5% of Multnomah County's mapped soils are free of severe limitations for a conventional septic drain field, so get Portland's septic program to evaluate any specific parcel before you close³⁰³¹. Ownership: about 38.4% of Multnomah County is federal land, which sharply limits how much of the county is even available to buy, so confirm a parcel's private status and boundaries carefully³⁶. Access: if you will need a new driveway onto a county road, budget about three weeks for the county's driveway permit process, plus a refundable deposit if you are paving³⁴³³. Climate and cost: the county averages about 63.4 inches of precipitation a year with roughly 9.4% of years in severe drought, a typical home insurance premium near $1,181 a year, and a typical property tax bill around $5,061 a year at an effective rate near 1%³⁷³⁸³⁹⁴⁰⁴¹.

Watch-outs

Multnomah County does not issue building permits itself, and Portland's Permitting & Development bureau covers only some unincorporated areas; confirm which office actually serves your parcel before you assume county or Portland rules apply¹⁴.
Camping or RV-park stays in county-regulated zones are capped at 90 days and are defined as temporary, not residential; that limit does not answer whether you can live in an RV on ordinary unincorporated land¹².
Only about 1.5% of Multnomah County's mapped soils are free of severe limitations for a conventional septic drain field; get Portland's septic program to evaluate any specific parcel before you buy³⁰³¹.
About 38.4% of Multnomah County is federal land; confirm a parcel's private ownership and boundaries carefully before you buy³⁶.

Sources

Written September 28, 2026 from the rules quoted below, each taken from an official source and re-checked by an independent reviewer. This is research, not legal advice: rules change, so confirm with the office before you buy or build.

How Multnomah County scores

Seclusion15100% ev.

Self-Sufficiency44100% ev.

Admin Boringness42100% ev.

Durability60100% ev.

Property Autonomy72100% ev.

Carry Cost29100% ev.

Evidence strength: 100%. This reports direct-source completeness and fallback use; it is separate from the score and is not a confidence interval. How it works →

$511kTypical home

1%Property tax

$27,472Land / acre

63.4"Annual rain

9.4% of yrsSevere drought

1.9 / yr (+1.5)Mid-century 100°F days

26.4 daysMid-century dry spell

2.24" (+3.9%)Mid-century 1-day rain

1.33×Wildfire change factor

100%Forward climate coverage

$1,181Home insurance / yr

3.2% / yrInsurance growth

0.55%Nonrenewal rate

county median (2+ published ZIPs)Insurance basis

1,457,701People within 30 min

3,825,009People within 2 hr

1,435,326Radius comparison (15 mi)

1,831.6People / sq mi

38.4%Federal land

55%Land at 15% slope or less

1.5%Septic soil without severe limits

3,096 acWorkable land screen

162.7 tonsBiomass / forest ac

51.8°FAvg temp

Answers from the rulebook for Multnomah County

What the ordinances and state agencies actually say — one answer per question, each quoted from the official source and independently re-checked.

Multnomah County rules

Building permitLimited
Building permits in unincorporated Multnomah County; the issuing city depends on the area, and Portland issues permits for some unincorporated areas.
- Multnomah County states that it does not issue building permits.
- Building permits in Multnomah County are issued by cities, including for areas outside city boundaries.
- Portland's page expressly limits its role to some areas of unincorporated Multnomah County.
“The City of Portland also issues building permits for Some areas of unincorporated Multnomah County”
Submitting a Building Plan ↗Re-checked Sep 24, 2026
InspectionsRequired
Permitted residential construction in unincorporated Multnomah County where the issuing jurisdiction requires the listed inspections; Portland's residential inspection rules apply to permits administered by Portland Permitting & Development.
- All permitted work must be inspected before it is covered by drywall, concrete, backfill, or similar concealment.
- New construction follows a full inspection sequence beginning with erosion control and foundation inspections and ending with final inspections.
- All permits need the 999 Final Permit inspection; a permit is not approved and closed until that inspection is completed.
- If a permit is without an approved inspection for more than 180 days, it will expire.
permit inspection expiration without approved inspection: 180 days
“All permitted work must be inspected before it is covered by drywall, concrete, backfill, etc.”
Residential Inspections: The Start-to-Finish Guide ↗Re-checked Sep 24, 2026
Certificate of occupancyLimited
New single-family dwelling units, duplexes, and accessory dwelling units in areas of unincorporated Multnomah County administered under the Portland residential certificate-of-occupancy program.
- Either a Certificate of Occupancy or Temporary Certificate of Occupancy is required before occupancy of all new residential construction of single-family dwelling units, duplexes, and accessory dwelling units.
- Certificates of Occupancy and Temporary Certificates of Occupancy are not required for residential additions, alterations, or accessory structures such as garages.
- A Certificate of Occupancy is issued after final inspections for all requirements related to the permitted project are inspected and approved.
- A Temporary Certificate of Occupancy may be requested when not all permitted work is complete, but minimum fire and life-safety requirements, applicable temporary erosion control, required discipline approvals, and the issuance fee must be satisfied.
temporary certificate duration: 30 days (Extensions may be granted for a maximum of 30 days each under the program guide.)
“Either a C of O or TCO is required prior to occupancy of all new residential construction of single family dwelling units, duplexes, and accessory dwelling units.”
Residential Certificate of Occupancy and Temporary Certificate of Occupancy ↗Re-checked Sep 24, 2026
County-wide zoningPresent (with conditions)
County zoning in Multnomah County, principally the unincorporated areas outside cities.
- Multnomah County is responsible for zoning in most unincorporated areas.
- Some unincorporated areas are administered by neighboring cities under intergovernmental agreements and have city zoning.
- Incorporated municipalities administer their own zoning.
“Multnomah County is responsible for zoning in most unincorporated areas of the County. Unincorporated areas are those areas located outside of a city.”
County Urban Pocket Areas ↗Re-checked Sep 24, 2026
Local zoningVaries (with conditions)
The county aggregate of local zoning across incorporated municipalities and unincorporated areas of Multnomah County.
- The county administers zoning in most unincorporated areas.
- Some unincorporated areas have city zoning administered by neighboring cities under IGAs.
- The City of Portland administers the Portland Zoning Code for specific areas of unincorporated Multnomah County.
- Property-specific jurisdiction and zoning must be verified using the county jurisdiction map or with the responsible planning authority.
“Some unincorporated areas are administered by neighboring cities and have city zoning. These areas are determined through Intergovernmental Agreements (IGAs) and are known as IGA areas.”
County Urban Pocket Areas ↗Re-checked Sep 24, 2026
Minimum dwelling sizeDistrict specific (with conditions)
Residential uses located in the Multnomah County Multiple Use Forest (MUF) base zone after August 14, 1980.
- The dwelling must comply with the listed MUF residential development standards.
- The dwelling must be attached to a foundation for which a building permit has been obtained.
- The dwelling must be outside a big game habitat area unless the Oregon Department of Fish and Wildlife certifies acceptable impacts.
minimum floor area: >= 600 square feet
“A residential use located in the MUF base zone after August 14, 1980, shall comply with the following: [...] The dwelling shall have a minimum floor area of 600 square feet.”
Chapter 39 – Multnomah County Zoning Code ↗Re-checked Sep 24, 2026
Minimum lot sizeSpecified
New parcels in the Exclusive Farm Use (EFU) base zone.
- The rule has an exception for MCC 39.3070.
- The EFU dimensional and development standards also apply.
minimum lot size: >= 80 acres (Except as provided in MCC 39.3070)
“Except as provided in MCC 39.3070, the minimum lot size for new parcels shall be 80 acres in the EFU base zone.”
Chapter 39 – Multnomah County Zoning Code ↗Re-checked Sep 24, 2026
2 more reviewed findings on this topic
- Specified — New parcels or lots in the Multiple Use Agriculture (MUA-20) base zone.
  “Except as provided in MCC 39.3080, 39.4330, 39.4335 and 39.5300 through 39.5350, the minimum lot size for new parcels or lots shall be 20 acres.”
  Chapter 39 – Multnomah County Zoning Code ↗Re-checked Sep 24, 2026
- Specified — New parcels or lots in the Rural Residential (RR) base zone.
  “Except as provided in MCC 39.3090, 39.4380, 39.4385 and 39.5300 through 39.5350, the minimum lot size for new parcels or lots shall be five acres.”
  Chapter 39 – Multnomah County Zoning Code ↗Re-checked Sep 24, 2026
SetbacksSpecified
Development in the MUA-20 base zone.
- Accessory structures may encroach up to 40 percent into a required yard only when the yard is not contiguous to a road, the structure does not exceed five feet in height or a ten-square-foot footprint, and fire-code compliance is demonstrated.
- A variance is required for an accessory structure encroaching more than 40 percent.
- Minimum yards increase where the yard abuts a street with insufficient right-of-way width.
- Agricultural structures may have a reduced rear yard to 10 feet under the stated dwelling-separation conditions.
front yard: >= 30 feet · side yard: >= 10 feet · street-side yard: >= 30 feet · rear yard: >= 30 feet (Agricultural structures may qualify for a reduced rear yard of 10 feet under MCC 39.4325(F))
“Minimum Yard Dimensions – Feet Front Side Street Side Rear 30 10 30 30”
Chapter 39 – Multnomah County Zoning Code ↗Re-checked Sep 24, 2026
Lot coverageSpecified
Development in the MR-4 base zone.
- The MR-4 dimensional requirements include exceptions under MCC 39.3140(B) and 39.4910(A)-(B).
maximum lot coverage: <= 40 percent
“The maximum lot coverage shall be 40 percent.”
Chapter 39 – Multnomah County Zoning Code ↗Re-checked Sep 24, 2026
Building heightSpecified
Structures in the MUA-20 base zone.
- Structures such as barns, silos, windmills, antennae, chimneys, or similar structures may exceed the height requirement if located at least 30 feet from any property line.
maximum structure height: <= 35 feet (Certain structures may exceed the limit if at least 30 feet from any property line)
“Maximum Structure Height – 35 feet [...] structures may exceed the height requirement if located at least 30 feet from any property line.”
Chapter 39 – Multnomah County Zoning Code ↗Re-checked Sep 24, 2026
Living in an RVTemporary only (with conditions)
Recreational vehicle occupancy in a county-regulated campground, campsite, or recreational vehicle park in applicable unincorporated Multnomah County zoning districts.
- The campground definition allows recreational vehicle occupancy for overnight temporary vacation, recreational, or emergency purposes, but not residential purposes.
- In MUA-20, RR, BRC, SRC, and RC base zones, the stay by a person or vehicle in a camp, campground, campsite, or recreational vehicle park may not exceed 90 days in any consecutive 12-month period unless otherwise provided in state law.
- The 90-day provision does not apply in the West of Sandy River Planning Area or Urban Planning Area.
- Camp, campground, and recreational vehicle park uses may require approval under the applicable base zone and planning-area provisions.
maximum stay: <= 90 days in any consecutive 12-month period (Unless otherwise provided in state law; not applicable in the West of Sandy River Planning Area or Urban Planning Area)
“the length of stay by a person or vehicle in a camp, campground, campsite or recreational vehicle park shall not exceed a total of 90 days during any consecutive 12 month period”
Chapter 39 – Multnomah County Zoning Code ↗Re-checked Sep 24, 2026
Camping on your landLimited
Temporary camping in county-regulated camps, campgrounds, campsites, and recreational vehicle parks in applicable unincorporated Multnomah County zoning districts.
- Camping is defined for overnight temporary vacation, recreational, or emergency purposes.
- A campsite may be occupied by a tent, travel trailer, or recreational vehicle, but not for residential purposes.
- In MUA-20, RR, BRC, SRC, and RC base zones, stay is limited to 90 days in any consecutive 12-month period, subject to state-law exceptions.
- The 90-day rule does not apply in the West of Sandy River Planning Area or Urban Planning Area.
maximum stay: <= 90 days in any consecutive 12-month period (Unless otherwise provided in state law; excluded planning areas stated above)
“Campground – An area improved with a campsite and/or used for an overnight temporary stay for vacation, recreational or emergency purposes”
Chapter 39 – Multnomah County Zoning Code ↗Re-checked Sep 24, 2026
Manufactured homesLimited
Permanent occupancy of manufactured homes in county-regulated mobile home parks in applicable unincorporated Multnomah County residential base zones.
- The manufactured home must be located in a compliant mobile home space.
- In LR-7 and LR-5 base zones, it must have been constructed after June 15, 1976 and carry a state insignia showing compliance with applicable Oregon mobile-home construction or equipment standards.
- The home must meet state construction standards evidenced by the required insignia.
- Other park standards include potable water and electrical and sewage-disposal connections, space-coverage limits, and separation distances.
construction date: > 1976-06-15 · minimum floor area: >= 800 square feet (For mobile homes in mobile home parks within LR-7 or LR-5 base zones; other zone-specific standards may differ)
“Any mobile home in a mobile home park within an LR-7 or LR-5 base zone shall: (1) Be located in a mobile home space”
Chapter 39 – Multnomah County Zoning Code — Mobile Home Park provisions ↗Re-checked Sep 24, 2026
Agricultural exemptionConditional
Farm use, including buildings and structures accessory to farm use, under the Significant Environmental Concern overlay provisions of Chapter 39.
- Farm use and accessory buildings generally do not require an SEC permit.
- Within the West of Sandy River Planning Area, an SEC-wr and/or SEC-sw permit is required for agricultural buildings, structures, and development associated with farm practices and agricultural uses; agricultural fences are excepted.
- Within Metro’s 2009 jurisdictional boundary, an SEC-s permit is required for agricultural buildings, structures, and development associated with farm practices and agricultural uses; agricultural fences are excepted.
- The code defines farm use by reference to ORS 215.203(2)(a).
“Farm use, as defined in ORS 215.203(2)(a), including buildings and structures accessory to a farm use do not require an SEC permit except in the following situations:”
Chapter 39 – Multnomah County Zoning Code ↗Re-checked Sep 24, 2026
Subdividing landRegulated (with conditions)
Subdivisions and other land divisions in unincorporated Multnomah County subject to Chapter 39.
- Every land division must comply with applicable MCC 39.9505 through 39.9585 standards.
- A rural area subdivision is a Category 1 Land Division.
- An urban area subdivision of more than 10 lots is a Category 1 Land Division.
- Urban subdivisions of 10 lots or less and partitions are assigned categories based on street, impact, overlay, and other criteria.
urban subdivision threshold for Category 1: > 10 lots (Urban subdivision of 10 lots or less may be Category 1 when specified street or impact criteria apply)
“Every land division proposal shall comply with the applicable provisions of MCC 39.9505 through 39.9585.”
Chapter 39 – Multnomah County Zoning Code ↗Re-checked Sep 24, 2026
Driveway accessRequired
Any new or altered access to a Multnomah County road, including driveway access in unincorporated areas.
- Some older driveways that never received a permit may need to be brought into compliance.
- The application requires a right-of-way permit application, site plan, proof of insurance, traffic-control plan, permit fee, and driveway deposit payment.
- A traffic-control plan conforming to MUTCD standards is required if the work is expected to interrupt or affect traffic.
- A deposit is required when paving or repaving a driveway and is refunded after construction passes inspection.
- The county says permits usually take about three weeks.
typical processing time: about three weeks
“A driveway permit is required for any new or altered access to a county road. In addition, some older driveways may have never received a permit and may need to be brought into compliance.”
Permitting a Driveway ↗Re-checked Sep 24, 2026
Short-term rentalsLimited
Accessory dwelling units regulated under the cited Multnomah County Zoning Code provision in unincorporated county areas.
- Short-term rental means fee-based occupancy for fewer than 30 consecutive calendar days.
- Month-to-month rental agreements for long-term purposes are excluded from the definition.
- The property owner must sign and record a covenant with the county stating that the ADU cannot be used for short-term rental.
- The covenant applies until the property is annexed into a city and is no longer subject to county land-use regulations.
- This source establishes an ADU-specific restriction, not a blanket countywide prohibition on every short-term rental.
short-term rental maximum duration: < 30 consecutive calendar days (Month-to-month long-term rental agreements are excluded)
“Short-term rental of the ADU is prohibited. For purposes of this subsection, short-term rental is defined as fee-based occupancy for a period less than 30 consecutive calendar days. Month-to-month rental agreements for long-term purposes are not short-term rental.”
Chapter 39 – Multnomah County Zoning Code, Multiple Use Agriculture ↗Re-checked Sep 24, 2026
Permit feesPublished (with conditions)
Multnomah County Land Use Planning fees for applications in unincorporated county areas.
- The fee schedule is effective July 1, 2026.
- The published schedule includes a Floodplain Development Permit fee of $1,620 and a Zoning Plan Check fee of $527.
- Applications are not identified as received until full payment is made; payment after 4:00 PM or outside regular business hours is received the next business day.
- Some Type II, III, and IV applications require notice fees, deposits, or full-recovery deposits; the Planning Director may require a full recovery deposit estimate when projected costs exceed the listed minimum.
Floodplain Development Permit fee: 1620 USD · Zoning Plan Check fee: 527 USD · effective date: 2026-07-01
“Multnomah County Land Use fee schedule effective July 1, 2026. [...] Floodplain Development Permit | $1,620 [...] Zoning Plan Check (new development, or new development and demo permit, or other site plan review) | $527”
Land Use Planning Fees ↗Re-checked Sep 24, 2026

Oregon rules that apply here

Owner-builder exemptionAvailable (with conditions)
Owner-built single-family residences and adjacent auxiliary structures in Oregon, including Multnomah County, when the statutory owner and construction conditions are met.
- The owner must be the owner of title or contract purchaser of record and must not have used the exemption during the five years before applying.
- The owner-built dwelling and outbuildings must be a single-family residence and adjacent auxiliary structures whose structural components are constructed entirely by the owner, or by the owner and unpaid friends and relatives, and the owner must intend to occupy the structures.
- The exemption applies only to structural-code requirements for ceiling heights, room sizes, and maintenance of specific temperature levels.
- The exemption applies to new construction, renovation, remodeling, or alteration of an owner-built dwelling or outbuilding.
- A building permit issued for the owner-built dwelling or outbuilding must note whether it complies with the exempted requirements.
- If it does not comply, the owner-builder must file a copy of the building permit with the county clerk for permanent deed recording and provide a sufficient property description.
- This exemption does not eliminate the building-permit requirement.
prior use lookback period: 5 years
“Owner-built dwellings and outbuildings shall be exempt from any requirements of the structural code for ceiling heights, room sizes and the maintenance of specific temperature levels in those structures.”
2023 Oregon Residential Specialty Code, Chapter 1 ↗Re-checked Sep 24, 2026
One more reviewed finding on this topic
- Available (with conditions) — Owner-built single-family residences and adjacent auxiliary structures in Oregon where the structural components are constructed entirely by the owner intending to occupy the structures, or by the owner with unpaid assistance from friends and relatives.
  “Owner-built dwellings and outbuildings shall be exempt from any requirements of the structural code for ceiling heights, room sizes”
  2023 Oregon Residential Specialty Code - ORS 455.320 reprinted ↗Re-checked Sep 12, 2026
Building code adoptedAdopted (with conditions)
The Oregon Residential Specialty Code applies statewide to construction, reconstruction, and repair of one- and two-family dwellings and townhouses, including applicable projects in Multnomah County.
- Administrative provisions, Chapter 1, were effective and mandatory October 1, 2023.
- Construction provisions, Chapters 2-44 and appendices, were effective October 1, 2023 with a six-month phase-in period and became mandatory April 1, 2024.
- The cited ORSC page states the code is based on the 2021 International Residential Code.
- This claim addresses the statewide residential code; other building types may be governed by other Oregon specialty codes.
administrative provisions mandatory date: 2023-10-01 · construction provisions effective date: 2023-10-01 (six-month phase-in period) · construction provisions mandatory date: 2024-04-01
“Construction provisions (Chapters 2 - 44 and appendices): Effective Oct. 1, 2023 with six-month phase-in period Mandatory April 1, 2024”
Residential Structures Code Program ↗Re-checked Sep 24, 2026
3 more reviewed findings on this topic
- Adopted (with conditions) — Oregon State Building Code specialty codes administered statewide by the Oregon Building Codes Division.
  “The Building Codes Division adopts, amends, and interprets specialty codes that make up the Oregon State Building Code.”
  Oregon State Building Code ↗Re-checked Sep 12, 2026
- Adopted (with conditions) — Commercial construction, reconstruction, alteration, and repair governed by the Oregon Structural Specialty Code statewide.
  “Construction provisions: [...] Mandatory April 1, 2026”
  Oregon Structural Specialty Code adoption ↗Re-checked Sep 12, 2026
- Adopted (with conditions) — Construction, reconstruction, and repair of one- and two-family dwellings and townhouses governed by the Oregon Residential Specialty Code statewide.
  “2023 Oregon Residential Specialty Code (ORSC) [...] Based on 2021 International Residential Code (IRC)”
  Residential Structures Code Program ↗Re-checked Sep 12, 2026
Zoning districtsPublished (with conditions)
Statewide Oregon zoning data published by the Department of Land Conservation and Development; the data represents local zoning and does not itself replace local zoning ordinances or maps.
- The source identifies the dataset as Statewide Zoning - 2023.
- The source provides downloads through GEOHub and a GIS service.
- Local governments remain the relevant authorities for parcel-level zoning determinations and ordinance administration.
dataset year: 2023
“Statewide Zoning - 2023 Downloads available from GEOHub Service”
Maps, Data and Tools ↗Re-checked Sep 12, 2026
Accessory dwellingsLimited
Accessory dwelling units in areas within an urban growth boundary zoned for detached single-unit dwellings in a city with population greater than 2,500 or a county with population greater than 15,000.
- The local government must allow at least one accessory dwelling unit for each detached single-unit dwelling.
- Local regulations may address siting and design but may not include owner-occupancy requirements for the primary or accessory structure or requirements to construct additional off-street parking.
- Local governments may regulate vacation occupancies to require owner-occupancy or off-street parking.
city population threshold: > 2500 persons · county population threshold: > 15000 persons · minimum ADUs per detached single-unit dwelling: >= 1 unit
“A city with a population greater than 2,500 or a county with a population greater than 15,000 shall allow”
Oregon Revised Statutes, ORS 197A.425 ↗Re-checked Sep 12, 2026
Who permits septicMixed
Residential and small-business septic permitting statewide in Oregon.
- DEQ directly permits residential and small-business septic systems in Curry, Jackson, and Josephine counties.
- In Oregon's other 33 counties, DEQ contracts with local jurisdictions for residential and small-business septic permitting.
“The Oregon Department of Environmental Quality permits residential and small business septic systems in Curry, Jackson, and Josephine counties out of the DEQ Medford Office. In Oregon's other 33 counties, DEQ has contracts with local jurisdictions for residential and small business septic permitting.”
Residential Septic Permitting ↗Re-checked Sep 12, 2026
Off-grid sanitationLimited
Use of composting toilets and related graywater systems in Oregon.
- A composting toilet does not eliminate all household water; plumbing fixtures still need connection to an approved septic system.
- If used with a graywater reuse system, both the graywater reuse system and septic system require a DEQ permit.
- The graywater reuse system must be offline during wet-weather months or when discharges could create a public nuisance.
- Material removed from a composting toilet must be buried under 12 inches of soil.
- Buildings within a sewer district still need a sewer connection.
burial depth for removed composting-toilet material: 12 inches · maximum reduced drainfield capacity mentioned by DEQ: two-thirds (The source says the drainfield may be approved for a smaller capacity, as much as two-thirds the size.)
“Composting toilets don't eliminate all water generated in a home and therefore you will need to be hooked up to an approved wastewater treatment system.”
What do I do with the finished material? ↗Re-checked Sep 12, 2026
One more reviewed finding on this topic
- Allowed (with conditions) — Development using onsite wastewater treatment or septic systems where municipal sewer is unavailable in Multnomah County.
  “In areas where a municipal sewer system is not available, development must use onsite wastewater treatment systems, or septic systems, for sanitary disposal.”
  Housing and Onsite Wastewater Management ↗Re-checked Sep 24, 2026
Mandatory utility hookupSewer (with conditions)
A building located within an Oregon sewer district, including a building using a composting toilet.
- The source specifically addresses buildings within a sewer district.
- A composting toilet does not eliminate the sewer-connection requirement.
“What if my building is within a sewer district? Your building will still need a sewer connection.”
What do I do with the finished material? ↗Re-checked Sep 12, 2026
Permit processPublished (with conditions)
Online homeowner building-permit applications through Oregon ePermitting in participating cities and counties.
- Participation by cities or counties is voluntary.
- Each participating city or county determines which permits are available for online sale.
- The applicant creates an account, downloads the homeowner acknowledgement form, searches for the work-site address, enters owner contact details, uploads the form, and enters work details.
- After submission, the local city or county contacts the applicant when fees are ready to be paid and when the permit has been issued.
- Applicants may track status, pay fees, upload documents, schedule inspections, and review inspection results after submission.
“Participation by cities or counties is voluntary and each participating city or county determines which permits are available for sale online.”
Online building permit application process for homeowners ↗Re-checked Sep 12, 2026
county zoning authorityGeneral
Oregon counties adopting and revising comprehensive plans, zoning, subdivision, and other land-use ordinances applicable to county land, including unincorporated areas.
- The statutory text states an exception for ORS 527.722.
- Plans and related ordinances may be adopted and revised part by part or by geographic area.
- Zoning, subdivision, and other ordinances or regulations must be designed to implement the adopted county comprehensive plan.
- Before a county zoning ordinance has legal effect, the governing body or planning commission must conduct one or more public hearings and publish 10 days' advance public notice; additional notice requirements apply to certain zone changes under ORS 215.223.
“Except as provided in ORS 527.722, the county governing body shall adopt and may from time to time revise a comprehensive plan and zoning, subdivision and other ordinances applicable to all of the land in the county. The plan and related ordinances may be adopted and revised part by part or by geographic area.”
Oregon Revised Statutes, Chapter 215 — County Planning; Zoning; Housing Codes ↗Re-checked Sep 21, 2026
county building authorityGeneral
Oregon counties administering and enforcing building inspection programs, including issuance and enforcement of building permits for residential construction in areas outside incorporated cities.
- A county building inspection program is subject to the state building code and the statutory building-inspection-program framework.
- If a county does not notify the director, or notifies the director that it will not administer and enforce a building inspection program, the director must arrange administration and enforcement through a municipality, other person, state employees, or state agencies; permit and other fees arising therefrom are paid into the Consumer and Business Services Fund.
- A building inspection program is administered for four-year periods under ORS 455.150; the governing body must provide required notices to the Director of the Department of Consumer and Business Services.
- The program must specify cooperation with the State Fire Marshal or designee and how a uniform fire code will be considered in design and construction review.
- The cited archive is the 2015 Oregon Revised Statutes edition; the current official ORS 455 page was identified but returned a 403 error during retrieval.
“If a city does not notify the director, or notifies the director that it will not administer the building inspection program, the county or counties in which the city is located shall administer and enforce the county program within the city in the same manner as the program is administered and enforced outside the city, except as provided by subsection (6) of this section.”
Oregon Revised Statutes, Chapter 455 — Building Code ↗Re-checked Sep 21, 2026

Inside cities and towns in Multnomah County

Municipal rules found while researching the county. They apply inside that city or town, not to unincorporated land.

Who permits septicLocal
Septic permitting and inspections throughout Multnomah County, including incorporated cities and named communities listed by the City of Portland.
- The City of Portland administers the program under an intergovernmental agreement with Multnomah County and Oregon DEQ.
- The City of Portland oversees administration of DEQ’s On-Site Wastewater Treatment Systems Rules.
“The City of Portland has an intergovernmental agreement with Multnomah County and the State of Oregon Department of Environmental Quality (DEQ) to conduct septic permitting and inspections for all of Multnomah County”
Septic Permits: New Construction, Repairs, and Alterations ↗Re-checked Sep 24, 2026
Septic inspectionRequired
Septic permits administered by Portland Permitting & Development for Multnomah County.
- The City of Portland conducts septic inspections for all of Multnomah County under its intergovernmental agreement.
- For all septic tank permits, an approved plumbing inspection for the sanitary line is required before the septic permit is final.
- If a pump is required, approved electrical inspections are required for underground trenching and the septic panel before septic final.
- Inspection schedules differ east and west of the Willamette River.
septic tank inspection code: 836 · drainfield inspection code: 814
“For all septic tank permits, an approved Plumbing inspection for the sanitary line is required before the septic permit is final.”
Septic Permits: New Construction, Repairs, and Alterations ↗Re-checked Sep 24, 2026

Each answer was extracted from an official source and independently re-checked against that source by a second reviewer. That is an evidence check, not legal advice. Rules change; confirm with the authority before you buy or build.

Living off-grid in Multnomah County, Oregon

Is Multnomah County a good place to live off-grid or homestead?

Multnomah County scores 38/100 on the Bolthole Index, a marginal county profile. Its strengths: a stronger property-autonomy legal backdrop and mixed durability signals. Watch-outs: little seclusion — roughly 1,457,701 people within a 30-minute drive and higher long-term carry cost.

Do you need a building permit in Multnomah County, Oregon?

Multnomah County generally requires a residential building permit, and it enforces county zoning. Onsite septic is permitted by City of Portland Permitting & Development (administering Oregon DEQ Onsite Wastewater rules via IGA). Owner-builders may act as their own contractor to build their home. These answers are quoted from official sources and independently re-checked. Rules change and cities within the county differ — always confirm with the county before you buy or build.

Can you live in an RV or tiny home on your land in Multnomah County?

Living in an RV on your own land in Multnomah County is limited to specific cases: Statewide rule. One residential-use recreational vehicle on a lot or parcel in an Oregon rural area, when a county elects to allow the use under ORS 215.490. The property must not be within an urban reserve. An owner-occupied single-unit dwelling must be sited on the property as the owner's primary residence. Confirm with the county before relying on it.

How much does land cost in Multnomah County, Oregon?

Land in Multnomah County runs about $27,472 per acre, based on the latest county data.

What is the water situation in Multnomah County?

Multnomah County gets about 63.4" of rain a year, with severe drought in roughly 9.4% of years.

How remote is Multnomah County?

A representative private-land location has about 1,457,701 people within a 30-minute drive and 3,825,009 within two hours. The road-network catchments count population across county lines and clusters of smaller cities; straight-line radius values remain available as a comparison.

Building permits, zoning and septic rules in Multnomah County, Oregon