Scale of houses

Portland’s zoning allowances use measurable standards such as limits for height, lot coverage, setbacks and yard area to define a building envelope that limits how large a single family house can be on a lot. While the building envelope allowance has remained relatively unchanged, the size of houses built has increased steadily as a nationwide trend. Larger homes can result in loss of space for yard, gardens or trees; more shading on adjacent lots; greater energy and material consumption; and less neighborhood compatibility.

What is currently allowed

Building coverage regulations and height limits currently control house size. On a 5,000 square foot lot for example, the maximum building coverage is 2,250 square feet and the maximum height is 30 feet.

Comparison of house sizes on 5,000 square foot lots
RulesResults
Maximum building coverage allowed (square feet) Maximum height (feet) Maximum house size allowed (square feet) Average house built in 2013 (square feet) Largest house built in 2013 (square feet)
2,250 30 (three stories) 6,750 2,680 4,461

Proposal: Limit the size of houses while maintaining flexibility in form.

  • Establish house size square foot limits proportional to lot size
  • Exclude basements, non-habitable attics and detached structures from size limits
  • Retain current code’s building coverage limits

The proposal would add a new square foot limit via a sliding scale tied to lot size.

Proposed house size limits based on lot size
Lot size (square feet) 2,500 5,000 7,500 10,000 12,500
Proposed house size (square feet) 1,750 2,500 3,000 3,500 3,750
5000 sq foot lot graphicClick to enlarge

To encourage detached garages and detached accessory dwelling units (ADUs), an additional 800 square feet would be allowed. This also helps break up the massing of a house by distributing the size throughout the lot.

one story, two stories, three stories graphicClick to enlarge

Houses could either be taller with a smaller footprint or shorter and more spread out, but not both. Three possible 2,500 square foot house configurations: Single level (left), wide two-story (middle), and narrower, deeper two-story (right).

Download the Residential Infill Project draft proposal booklet.