Astoria, Oregon — what state law requires the city to allow on a residential lot

What it is, legally

Built on the parcel to the Oregon Residential Specialty Code, inspected in place. This is the baseline category the others are defined against — ORS 446.003 excludes anything built to that code from the definition of a manufactured dwelling.

What it turns on

• The lot meets the city’s dimensional standards for the district.
• Connection to municipal water and sewer, where the city requires it.

Ask the county

• Ask the city’s planning department for the district’s setback, height and lot coverage standards, and whether any overlay applies to the lot.
• Ask what system development charges apply to a new dwelling — inside a city these are commonly a five-figure line item that no listing mentions.

Who decides what

• Building code · Settled statewide

  The Oregon Residential Specialty Code is statewide. Counties administer it and inspect to it; they do not write their own.

  Ask: Nothing on the code itself. Ask which edition is in force and whether the county has adopted any local wildfire construction provisions, which is the one area where local additions are common. source

• Setbacks, height, lot coverage and road frontage · The county decides

  Set district by district in the county's code. On rural land the setbacks from property lines, from the road, and — in farm and forest districts — from adjoining resource operations are the standards most likely to decide where on the parcel a house can go, or whether an odd-shaped parcel can hold one at all.

  Ask: Ask for the district's dimensional standards and any resource-land buffer setbacks, and whether the parcel meets the road frontage or access standard.

What it is, legally

A building manufactured or assembled in whole or substantial part using closed construction at an off-site location, as defined in ORS 455.010, and regulated by the state Building Codes Division rather than by the county. Once sited it is a building like any other: it is NOT a manufactured dwelling, and the rules that follow manufactured dwellings do not follow it.

Commonly confused with

• A manufactured home. The two are separate legal categories with separate law. A prefabricated structure is built to the same state building code as a site-built house; a manufactured home is built to the federal HUD standard. Which one a supplier is selling determines which rules apply, and marketing language does not reliably distinguish them.

What it turns on

• The lot is zoned to allow single-family dwellings.
• The unit is a prefabricated structure under ORS 455.010, certified by the state Building Codes Division.

Ask the county

• Ask the city to confirm the lot is in a district that allows single-family dwellings — that is what triggers ORS 197.478.
• Ask whether the lot is in a historic district or adjacent to a historic landmark, which is the one exemption.

Who decides what

• Construction standard and plan approval · Settled statewide

  A prefabricated structure is built off site to the state building code under the Building Codes Division's Prefabricated Structures Program, which approves the plans and inspects the factory. The county building official inspects only what happens on site — foundation, connections, and any site-built portion.

  Ask: Ask the supplier for the state insignia of compliance and the approved plans; the county will need the on-site work permitted separately. source

• Setbacks, height and lot coverage · The county decides

  Once placed it is a building like any other, so the district's dimensional standards apply exactly as they would to a site-built house — and nothing more, since it is not a manufactured home and the placement standards for those do not reach it.

  Ask: Ask for the district's setback, height and lot coverage standards. If the county cites manufactured-home placement standards, point out that a prefabricated structure under ORS 455.010 is a different category.

What it is, legally

A residential trailer, mobile home or manufactured home under ORS 446.003 — built on a chassis to the federal standard rather than to the state building code. The statute is explicit that a unit meeting the definitions of both a manufactured dwelling and a recreational vehicle, but not identified by the manufacturer as a recreational vehicle, is a manufactured dwelling.

Commonly confused with

• A modular or prefabricated building, which is a different legal category built to a different code.
• A park model recreational vehicle. The manufacturer's own identification of the unit is what separates them under ORS 446.003, not size, appearance or how it is marketed.

What it turns on

• The lot is zoned to allow single-family dwellings.
• The lot is not in a historic district or adjacent to a historic landmark.

Ask the county

• Ask the city to confirm the lot is in a district that allows single-family dwellings.
• If the city cites appearance or design standards specific to manufactured homes, ask which statewide-goal protective measure they rest on — ORS 197.478 allows nothing else.

Who decides what

• Foundation, anchoring and installation · Settled statewide

  Every manufactured dwelling installed in Oregon is installed to the Oregon Manufactured Dwelling Installation Specialty Code — foundation, tie-downs, wind anchoring, setup — administered by the state Building Codes Division and inspected under it. This is the same everywhere in the state. A county planner cannot waive it and does not set it.

  Ask: Nothing to ask the county here. The installer works to the state code; ask the installer which edition applies and for the certified installation. source

• Construction standard of the unit itself · Settled statewide

  A manufactured home is built to the federal HUD standard, not to the state building code, and Oregon regulates the units and their dealers under ORS chapter 446. A county does not inspect the construction of the unit.

  Ask: Ask the dealer for the HUD certification label and data plate. The county will ask for them at permit time. source

• Placement standards · The county decides

  Outside an urban growth boundary a county's code can carry placement standards for manufactured homes beyond what it asks of a site-built house, and many do. They are drawn from a short, long-standing statutory template, so the kinds are predictable even where the figures are not: whether the unit must be multi-sectional; a minimum floor area; how high the unit may sit above grade and whether the perimeter must be enclosed; a minimum roof pitch; exterior siding and roofing comparable to nearby houses; a certified thermal envelope; and sometimes a limit on the unit's age. Inside a UGB, ORS 197.478 removes all of these except a thermal-envelope requirement.

  Ask: Ask for the county's placement standards for a manufactured home in this district, in writing, and specifically whether there is an age limit on the unit — that one decides whether a used home is an option at all. source

• Setbacks, height and lot coverage · The county decides

  The district's dimensional standards apply to a manufactured home as they would to any dwelling. They are set district by district and revised with the code.

  Ask: Ask for the district's setback, height and lot coverage standards, and whether any overlay on the parcel changes them.

What it is, legally

A vehicle designed for human occupancy and to be used TEMPORARILY for recreational, seasonal or emergency purposes, under ORS 446.003. The word temporarily is doing the work: a recreational vehicle is not a dwelling in Oregon law, so permission to live in one is a separate question from permission to have a dwelling, and it is answered by separate rules. A park model recreational vehicle is a recreational vehicle. A tiny home built on a trailer chassis is generally one too.

Commonly confused with

• A tiny home on a permanent foundation, which is not a recreational vehicle at all and is assessed as whichever dwelling category it was built under.
• A manufactured home. Under ORS 446.003 a unit meeting both definitions is a manufactured dwelling unless the manufacturer identified it as a recreational vehicle — so the factory label decides this, and it is worth reading before buying rather than after.

What it turns on

• The city’s code allows occupancy of a recreational vehicle on the lot, and on what terms.

Ask the county

• Ask the city whether an occupied recreational vehicle or tiny home on wheels is allowed on a residential lot, whether that depends on a house already being there, and for how long.
• Ask what the city treats a park model or a tiny home on wheels as — a recreational vehicle, or something else.

Who decides what

• Baseline occupancy on private land · Settled statewide

  ORS 446.125 generally permits a person to occupy a camping vehicle on privately owned land with the owner's consent, provided the land has adequate area for a safe and approved water supply and sewage disposal and the occupant meets state and local sanitation, water, plumbing and electrical standards. It is a habitability provision, not a land use permission — it does not override zoning — but it is why the sanitation question comes first in nearly every conversation about this.

  Ask: Ask what water supply and sewage disposal the county will accept for a recreational vehicle on the parcel — that question is decided before the zoning one is reached. source

• Where a county may not prohibit occupancy · Settled statewide

  ORS 197.493 generally bars a local government from prohibiting residential occupancy of a recreational vehicle, or limiting how long it may be occupied, solely because it is a recreational vehicle, in three situations: where ORS 215.490 applies; where the vehicle is in a manufactured dwelling, mobile home or RV park and is lawfully connected to water, power and sewage disposal; and where the dwelling on the lot was made uninhabitable by a natural disaster, for a limited period. A county saying occupancy is not permitted is generally speaking about ordinary private land, and those three are worth raising by name.

  Ask: If one of the three situations applies, ask the county how it treats it, citing ORS 197.493. source

• Zoning treatment of an occupied vehicle · The county decides

  Outside those situations, whether a recreational vehicle may be lived in on a parcel, for how long, and on what conditions is the county's zoning code — set district by district, and the part that varies most from county to county.

  Ask: Ask whether an occupied recreational vehicle is allowed in this district, whether that depends on a house already being there, for how long, and whether temporary occupancy during construction of an approved dwelling is a separate route.

What it is, legally

A structure with no dwelling use. Where it qualifies as an agricultural building on a farm, ORS 455.315 exempts it from the structural code and from a building permit — but that exemption is narrower than it is usually understood to be, and what it does not cover is set out per district below.

Commonly confused with

• A shop with living quarters, sometimes marketed as a barndominium. The living part is a dwelling and is assessed as one; the exemption for agricultural buildings does not reach it.

What it turns on

• The building meets the city’s size, height, setback and lot coverage standards for accessory structures.

Ask the county

• Ask the city what size an accessory structure may be before it triggers additional review, and whether a shop with plumbing or living space is treated differently.

Who decides what

• Agricultural building exemption · Settled statewide

  ORS 455.315 is statewide. What it exempts — the structure of an agricultural building on a farm, from the structural code and a building permit — and what it does not — electrical, plumbing, mechanical, and land use approval — does not vary by county.

  Ask: Ask the planning department, not the building official, whether the parcel qualifies as a farm for the exemption; the statute leaves that determination to them. source

• Size, height, setbacks and permit threshold · The county decides

  Where the exemption does not apply, the county's code sets how large an accessory building may be before it needs a permit or triggers review, its height, and its setbacks — and whether a shop with plumbing or a sleeping area is treated as something other than an accessory building.

  Ask: Ask the size below which no building permit is needed, the height limit, the setbacks, and how the county treats a shop that has plumbing or living space.