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Five counties have had their own code read — the rest answer from state law:

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Empty lots

What can go on an empty lot, on which kind of land

Five kinds of structure, five kinds of land. The answer turns on the district a lot sits in far more than on the county — and inside a city it stops turning on the county at all.

General planning information, not legal advice. Describes what generally applies in a district, not a specific property. Confirm with the county — how this works.

At a glance

What can go on an empty lot, by kind of land, from Oregon statewide law
Kind of structureExclusive farm useForestMixed farm and forestRural residentialInside a city
Site-builtHouse, built on site — Exclusive farm use: available with conditions. What that means.House, built on site — Forest: available with conditions. What that means.House, built on site — Mixed farm and forest: available with conditions. What that means.House, built on site — Rural residential: generally available. What that means.House, built on site — Inside a city: generally available. What that means.
PrefabModular or prefab building — Exclusive farm use: available with conditions. What that means.Modular or prefab building — Forest: available with conditions. What that means.Modular or prefab building — Mixed farm and forest: available with conditions. What that means.Modular or prefab building — Rural residential: available with conditions. What that means.Modular or prefab building — Inside a city: generally available. What that means.
ManufacturedManufactured home — Exclusive farm use: available with conditions. What that means.Manufactured home — Forest: available with conditions. What that means.Manufactured home — Mixed farm and forest: available with conditions. What that means.Manufactured home — Rural residential: available with conditions. What that means.Manufactured home — Inside a city: generally available. What that means.
RV / on wheelsRV, park model or tiny home on wheels — Exclusive farm use: generally not available. What that means.RV, park model or tiny home on wheels — Forest: generally not available. What that means.RV, park model or tiny home on wheels — Mixed farm and forest: generally not available. What that means.RV, park model or tiny home on wheels — Rural residential: available with conditions. What that means.RV, park model or tiny home on wheels — Inside a city: a local question. What that means.
Barn / shopBarn, shop or outbuilding — Exclusive farm use: generally available. What that means.Barn, shop or outbuilding — Forest: generally available. What that means.Barn, shop or outbuilding — Mixed farm and forest: generally available. What that means.Barn, shop or outbuilding — Rural residential: available with conditions. What that means.Barn, shop or outbuilding — Inside a city: available with conditions. What that means.
  • generally available
  • available with conditions
  • generally not available
  • a local question

The district decides, not the county — every county has land in several of these columns. Statewide law; the county’s own standards come on top. Any cell opens what it means for that kind of land.

Under which circumstances

What “conditions” means in each column. Statewide law; the county’s or city’s own standards come on top, and every district page says which questions are theirs.

Exclusive farm use

Land zoned primarily to protect commercial agriculture. New dwellings are generally not allowed unless a narrow statutory test is met, and those tests are fact-intensive rather than automatic.

  • Site-builtAvailable with conditions
  • PrefabAvailable with conditions
  • ManufacturedAvailable with conditions
  • RV / on wheelsGenerally not permitted
  • Barn / shopGenerally available

A house is not a right here; it is one of several narrow statutory routes decided by the county on the parcel’s own facts — lot of record, unsuitability for farm use, a farm dwelling meeting the income test, replacement of a lawful dwelling. Which kind of house is a later question. A barn is generally the most available thing, and the permit exemption for it is narrower than it sounds. An RV is not a dwelling here at all.

What varies by county, county by county

Forest / conservation

Land zoned primarily to protect forest use and conservation values. New dwellings are generally not allowed except through narrow statutory tests, often with additional fire-related siting requirements.

  • Site-builtAvailable with conditions
  • PrefabAvailable with conditions
  • ManufacturedAvailable with conditions
  • RV / on wheelsGenerally not permitted
  • Barn / shopGenerally available

As for farm land, with the template test in place of the farm routes: a dwelling depends on how many lots and dwellings stood within a 160-acre square around the tract on 1 January 1993 — so two parcels in the same district can reach opposite answers, and the county runs the count.

What varies by county, county by county

Mixed farm and forest

Land zoned for a mix of farm and forest use, typically in larger parcels. Dwelling approval is generally constrained and depends heavily on parcel history and the specific county's provisions.

  • Site-builtAvailable with conditions
  • PrefabAvailable with conditions
  • ManufacturedAvailable with conditions
  • RV / on wheelsGenerally not permitted
  • Barn / shopGenerally available

The county’s own provisions govern, drawing on both the farm and the forest routes. Which route applies is the county’s first determination and is worth asking before anything else.

What varies by county, county by county

Rural residential

Land zoned to allow rural living on acreage. This is generally where a first dwelling is most likely to be achievable, and where second-dwelling options such as accessory dwellings or RVs are most likely to be available if the county permits them at all.

  • Site-builtGenerally available
  • PrefabAvailable with conditions
  • ManufacturedAvailable with conditions
  • RV / on wheelsAvailable with conditions
  • Barn / shopAvailable with conditions

A first dwelling is what the district is for, subject to approved sanitation, legal access and the district’s standards — and on a vacant parcel the sanitation question comes first, because it decides whether anything can be built. Prefab and manufactured homes are conditional on county standards. An RV as a dwelling depends on the county having adopted the state option, which 3 of 36 have, and on a house already being there.

What varies by county, county by county

Urban residential

Land inside an urban growth boundary zoned for housing — inside a city, or unincorporated county land the city will one day annex — generally on smaller lots with urban services available or planned. Rural-specific pathways do not apply; two statewide statutes bind by city size instead.

  • Site-builtGenerally available
  • PrefabGenerally available
  • ManufacturedGenerally available
  • RV / on wheelsNot yet researched
  • Barn / shopAvailable with conditions

Inside an urban growth boundary the answer stops varying by county and is set by state law and the city’s population: a manufactured or prefabricated home must be allowed wherever a house is, on the same terms; an accessory dwelling is required with every detached house above 2,500; a duplex on every single-family lot above 2,500. An RV is the city’s own call. What remains is the city’s dimensional standards and system development charges. One kind of lot sits between these columns and is not answered here: county-administered land inside a growth boundary but outside city limits, where the county’s urban-area provisions govern.

Every city, by what state law requires

Where it varies, by place

Rural land — every countyWhat a buyer can do that changes county by county: an ADU on rural residential land, and an RV as a second home. Everything else is statewide.Inside a city — every cityWhat state law settles for a lot by the city’s population: an ADU, a duplex, other middle housing. The city’s own standards come on top.

Have a listing? The search on the home page reports the district and answers for it. Know the county and district already? The planner refines the answer for one parcel.