Multnomah County, OR zoning map, flood zone and property lines by address
Free, no account. Or open the Oregon map and tap a lot.
Towns in Multnomah County: Portland, Gresham, Lents.
Flood zone by address
ParcelSheet reads FEMA's National Flood Hazard Layer at the lot: the zone, whether it is a high risk area where lenders ask for flood insurance, and the base flood elevation where FEMA lists one. FEMA's countywide study for Multnomah County has 68 FIRM panels, the newest effective February 2019; no coastal V zones are mapped in it.
The official panel and any Letter of Map Amendment are at FEMA's Map Service Center. An elevation certificate for a Multnomah house comes from a licensed surveyor and is often on file with the county or city building office.
Property lines
The parcel outline, parcel number and mapped size come from the Oregon county parcel layers (each county publishes its own), so a Multnomah lot shows the same lines the county assessor draws. Multnomah County covers about 275,848 acres of land and 21,757 acres of water.
Mapped lines are approximate. The Multnomah County assessor keeps the parcel record (Multnomah County website); a licensed surveyor sets the true corners.
Zoning
Multnomah County zones its unincorporated land, and Portland, Gresham each zone the land inside their limits. ParcelSheet shows the use the county assessor lists for the lot and links the county planning department for the district, the uses it allows and the lot size it needs.
ADU and guest houses
Under Oregon's county land use planning law (Oregon Revised Statutes Chapter 215), local governments can allow an accessory dwelling unit on a lot with a house. Whether a Multnomah lot can add one depends on its district; the county planning department has the rule. ParcelSheet shows the mapped lot size and the ground's slope, the first two things the question turns on.
Septic and soil
ParcelSheet reads the USDA soil survey at the lot: the soil's name, its septic absorption rating and whether it is prime farmland. Multnomah County is soil survey area OR051, Multnomah County Area, Oregon, last updated September 2026, on Web Soil Survey.
A new or changed septic system in Multnomah County needs a permit from the Multnomah County onsite septic program office (run by the county or by Oregon DEQ, under DEQ onsite rules).
Setbacks
Setbacks in Multnomah County come from the zoning district: the front, side and rear distances a house must keep. ParcelSheet does not draw setback lines; the county zoning office gives them for the lot's district, and Portland and Gresham for land inside their limits.
Hazards that apply
- Wetlands and wildfire. ParcelSheet shows the National Wetlands Inventory near a Multnomah lot and the Forest Service wildfire hazard rating at it.
Questions
Is my house in a flood zone in Multnomah County?
Type the address in the box above and ParcelSheet reads FEMA's flood zone at the lot's center. FEMA's countywide flood map for Multnomah County has 68 panels, the newest effective February 2019. A lender or insurer uses the official FIRM panel; FEMA's Map Service Center has it.
How do I find property lines in Multnomah County?
Open the Oregon map, type the address, and the parcel outline from the Multnomah County assessor shows on the map with its parcel number and mapped size. Mapped lines are approximate; only a licensed surveyor sets the true corners.
What is my property zoned in Multnomah County?
Zoning in Multnomah County is set by the county for unincorporated land and by each city (such as Portland, Gresham) inside its own limits. ParcelSheet shows the use code the county assessor lists and links the office that sets the zoning; the planning office has the final word.
Can I build an ADU in Multnomah County?
Under Oregon's county land use planning law (Oregon Revised Statutes Chapter 215), counties and cities can allow an accessory dwelling unit, and each sets its own rules. In Multnomah County ask the zoning office for the lot's district first; ParcelSheet shows the lot size as mapped so you can see the room you have.
Do I need a septic permit in Multnomah County?
Yes. A new or changed septic system in Multnomah County needs a permit from the Multnomah County onsite septic program office (run by the county or by Oregon DEQ, under DEQ onsite rules). ParcelSheet shows the USDA soil survey's septic rating at the lot, from survey area OR051 (Multnomah County Area, Oregon).
What can I build on 5 acres in Multnomah County?
Zoning in Multnomah County is set by the county for unincorporated land and each city inside its own limits (such as Portland, Gresham). The zoning district decides the uses, how many homes and the smallest lot it allows on 5 acres. ParcelSheet shows the lot size as mapped and the use code on the parcel record; the planning office has the district and its rules. See the Multnomah County website.
What are the residential setbacks in Multnomah County (2026)?
Setbacks in Multnomah County come from the zoning code of the county, or of the city when the lot is inside city limits: the front, side and rear distances depend on the lot's district. ParcelSheet does not draw setback lines or give a number it did not read; the zoning office gives them for the district. See the Multnomah County website.
Next to Multnomah County: Clackamas County, Columbia County, Hood River County, Washington County.
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