The state's House and Senate have now both passed a measure that requires cities with more than 10,000 people to allow duplexes in areas zoned for single-family homes. In the Portland metro area it goes a step further, requiring cities and counties to allow the building of housing such as quadplexes and "cottage clusters" of homes around a common yard.

This type of housing is often called "missing middle" housing — that is, everything between single-family homes and mid- or high-rise apartment buildings. Buildings such three-flats or courtyard apartments used to be common, but many communities made them illegal, often as part of a strategy for racial and class segregation.

Rep. Julie Fahey, a Democrat from Eugene, worked with Kotek on the bill. Many people "might not be able to afford to buy a detached single-family home," she told Oregon Public Broadcasting. "The prices of those starter homes are rising further and further out of reach. So to have duplexes, to have town homes, those sort of things ... is really important."