Residential Infill and Middle Housing Land Divisions in Single-Dwelling Zones
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Source: Residential Infill and Middle Housing Land Divisions in Single-Dwelling Zones ↗ Last modified: Sun, 19 Apr 2026 20:05:42 GMT
The City of Portland’s single-dwelling zones govern the types of housing permitted in our neighborhoods.
The variety of housing options in Portland’s neighborhoods includes
- multiple accessory dwelling units (ADUs)
- duplexes
- triplexes
- fourplexes
- cottage clusters (a detached housing option)
Required standards in the Zoning Code include adopted limits on the size and scale of residential development.
Residential infill options: more flexibility for how you use lots
In zones R2.5, R5, R7, R10 and R20, the residential infill options add flexibility to what you build by:
- Increasing the number of units you can build on each lot
- Increasing the number of allowable configurations on lots
- Removing off-street parking requirement in single-dwelling zones
- Allowing detached housing developments called cottage clusters
Residential Infill Options: Learn about the different residential infill options. ↗
Narrow lots: For lots less than 32 feet wide, additional rules will apply. ↗
Limits to building size
Floor area ratio (FAR)
A requirement to measure each building’s floor area ratio on the lot limits the size of buildings.
FAR resources:
- Floor area ratio and how it might affect your project ↗
- How to calculate floor area in single-dwelling zones ↗
Building height
Height limits also determine how tall a building is allowed to be.
Measuring height: Learn how height is measured. ↗
Find out if your lot can have more units
A duplex is allowed on all single-dwelling zoned lots where a primary structure is allowed, with the exception of the RF (Residential Farm Forest) zone.
Residential infill option housing types are not allowed in lots in the z overlay on the zoning map. Lots in the z overlay have flooding, landslides, environmental zoning, or wildfire hazard.
See Portland City Code 33.418, Constrained Sites Overlay Zone ↗ for a complete list of the constraints that require application of the z overlay.
You cannot build more than two units on lots that are on unmaintained streets ↗, unless they have frontage on a dedicated pedestrian or bike connection that leads to a maintained street.
Minimum lot size requirements
The minimum lot size for most housing options is shown below:
- Zone R2.5: 1,500 square feet
- Zone R5: 3,000 square feet
- Zone R7: 4,200 square feet
- Zone R10: 6,000 square feet
- Zone R20: 12,000 square feet