A new bill has passed in the Washington State Senate that would allow townhomes and duplexes in predominantly single-family home areas. The bill, referred to as the “middle housing bill,” was introduced in the state House of Representatives in an effort to add one million homes to the state over the next 20 years.

“Suburban communities around Seattle have left it to Seattle to bear the burden of the growth that the whole region needs to take,” Seattle City Councilmember Dan Strauss told a local NPR station. “Now, they’re going to have to wrestle with that.”

The bill that passed through the House would have met approximately 20% of the state’s housing needs by allowing duplexes, four-plexes and six-plexes capable of housing more families with less space than traditional single-family homes. The Senate bill has relaxed some of those original contingencies, though: the new version of the bill only requires small- and mid-sized cities to allow duplexes.

The bill will return to the House, where the state representatives can choose to accept or reject the amendments. With bipartisan support in both the Senate and the House, the legislation is likely to end up on the governor’s desk in one form or another, meaning the higher-density housing should be showing up in Seattle suburbs in the next few years.