Can you live off-grid in Multnomah County, Oregon?
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Major concerns
Possible, but hard and costly. The ground is steep, with slopes averaging about 25%. That raises the cost of a driveway, septic, and foundation. Water is easy here, with about 52 inches of rain a year and wells near 140 feet. Solar is weaker here, about 3.9 hours of full sun a day, so plan a bigger battery bank or a generator.
What the land says
Rain
Rain can supply much of a household's water with a large tank. A garden mostly waters itself in normal years.
About 52 inches a year (PRISM, 1991 to 2020 average)
Wells
Shallow wells, so drilling should be one of the cheaper costs.
The typical well here is about 140 feet deep; a well typically runs $9,000 to $19,000
Growing season
A full season for most vegetables.
About 211 frost-free days, USDA zone 8b; last frost about April 19, first about November 4
Sun
Weak sun. Solar needs a generator behind it in winter.
About 3.9 hours of full sun a day, averaged over the year
Flood
Flood zones run along creeks and rivers here. Look up the parcel on FEMA's flood map.
FEMA maps flood zones within a quarter mile in places
Wildfire
Low wildfire risk.
U.S. Forest Service wildfire hazard map: Very Low to Moderate here
Storms
Hurricanes and strong tornadoes are rare here.
NOAA: no hurricane-strength storm within 50 miles since 1975; about 0.3 strong (EF2 or stronger) tornadoes a decade within 25 miles
Earthquakes
Strong shaking is possible. Build to the seismic code and brace the water tank.
USGS seismic hazard map: high
Terrain
Steep. A flat house site and a driveway route will drive the cost.
Slopes average about 25%, about 470 feet above sea level
Soil
Expect a costlier septic system, because rock or a hard layer sits about 38 inches down. The county's soil test decides.
Silt loam, well drained (USDA soil survey). A mound, sand filter, or treatment unit typically runs $10,000 to $20,000
Road
Paved roads are close by.
Nearest paved road usually within about 0.4 miles (OpenStreetMap)
Check an Oregon parcel, or plan the one you own
Get a free 0-100 off-grid score.
A step-by-step build plan, sizing your solar, water, garden, septic, heat, and buildings.
Is it legal here?
Zoning
Multnomah County zones land outside its towns and publishes its zoning map. Our free lookup shows the district for any address.
Building code
Oregon's building code applies uniformly statewide, including the Oregon Residential Specialty Code for houses (based on the International Residential Code), and cities and counties cannot set different requirements without state approval. City or county building departments issue house permits and inspect, and the state Building Codes Division does it for some counties.
Rainwater
Collecting it is allowed.
Composting toilets
Allowed.
Water rights
Water belongs to whoever claimed it first. A new well or pond may need a state permit, and a creek may already be claimed.
Drilled to about 140 feet, with pump and pressure tank
Septic
$10,000 to $20,000
Mound, sand filter, or treatment unit
Solar and batteries
$19,000 to $36,000
Sized for a modest household
Road or driveway
$4,000 to $10,000
From the nearest road to a house site
Clearing
$1,000 to $5,000
A house site, solar, and garden
Total
$42,000 to $90,000
Before the house
Before you make an offer on land here
Soil test
Get a soil test before you count on septic.
Rock or a hard layer sits about 38 inches down, which can rule out a standard system.
Flood map
Look up the parcel on FEMA's flood map.
Flood zones run along creeks and rivers here. Building in one means flood insurance and extra permits.
Zoning
Look up the parcel's zoning district with our free tool.
The county publishes its zoning map.
Nearby counties
789,698 people live in Multnomah County, about 1832.2 per square mile. It ranks 22nd of the 36 Oregon counties we scored, and Oregon ranks 46th of 50 states.