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Maps show 30 percent of Portland lots could host backyard homes

70,863 of the tax lots in Portland (about 30 percent) may be prime for ADU development.

A solution to Portland’s housing crisis could be in your own backyard. New data from the Institute for Sustainable Solutions shows over 70,000 single family residential lots in Portland, about 30 percent, could host a second small home on their property. That’s good news in a city with a sparse inventory of available housing and some of the fastest rising rents in the nation.

Known as Accessory Dwelling Units or ADUs, these small backyard homes can ease the housing shortage and offer an affordable option for people who might otherwise be forced out of their neighborhood due to rising housing costs.

Urban planning graduate student Sachi Arakawa analyzed the data and developed the GIS maps during an internship with the Institute for Sustainable Solutions. The maps are part of the Institute’s Small Backyard Homes Initiative, which aims to make it easier and more affordable for Portland homeowners to construct an ADU on their property.

Check out the data below. Click the map images to enlarge.

29,363 of the lots prime for ADU development are also within 500 feet of a transit stop.

3,860 of the prime lots are on an alley, which could allow for a clustering of ADUs that use the alley as a thoroughfare.

A walk score is a measure of a neighborhood's “walkability,” or how easy it is to get to places like like grocery stores, schools, and restaurants by walking.

Portland has some of the fastest rising rents in the nation. ADUs could help ease that trend by creating more housing options in existing urban space. Rental data analysis by students in Dillon Mahmoudi’s GIS for Community Development class.

Here’s a breakdown of the preliminary data on Portland lots that could accommodate ADUs. 

  • 70,863 of the tax lots in Portland (about 30 percent) are prime for ADU development.* 
  • 29,363 of those lots are within 500 feet of a transit stop.
  • 3,860 of those lots are on an alley, which could allow for a clustering of ADUs that use the alley as a thoroughfare.

» You might also be interested in this: Students create preliminary ADU designs for Small Backyard Homes Initiative



*The criteria for determining prime lots: Zoned single family residential: R 2.5, R5, or R7; Lot is 5000 sq. ft. or larger; There's no existing ADU on property; Lot is outside of historic landslide zones; Primary dwelling is at least 118 sq. ft. (so the ADU can be 100 sq. ft. or greater); Lot has a buildable environment of at least 667 sq. ft. (so it can hold an ADU of at least 100 sq. ft.) and allows for at least 250 sq. ft. of outdoor area (so total area is at least 917 sq. ft.).