Introduced as the “Grand Bargain” between new market-rate development and affordable housing, MHA was the centerpiece of then-Mayor Ed Murray’s Housing Affordability and Livability Agenda (HALA), a collection of 65 recommendations for addressing the housing crisis.

The policy has served as a lightning rod in the midst of Seattle’s rapid population boom and the accompanying spike in the cost of living.

Supporters, including city council members, affordable housing developers and density advocates, say MHA is a balanced approach to growth that will create much-needed affordable housing while allowing for construction of more market-rate housing to meet increasing demand.

Some detractors, many of them homeowners in Seattle, fear the upzones will irrevocably change the single-family neighborhoods that make up so much of Seattle without creating enough affordable housing to address actual need. On the other side of the same coin, some pro-development skeptics of MHA say it will hinder construction by adding excessive fees, defeating the city’s stated goal of building housing to meet the demands of a growing population.

MHA spent a year in legal limbo after 26 neighborhood groups called Seattle Coalition for Affordability, Livability, Equity (SCALE) appealed to the city hearing examiner on the grounds that the city had done insufficient analysis of MHA’s impact.

Today’s vote is not the council’s first go at MHA. As a forerunner to the citywide version, Seattle has already implemented MHA in six neighborhoods – Downtown, Belltown, South Lake Union, Chinatown-International District, University District, and at three intersections along 23rd Avenue in the Central District.

On Monday, the council adopted the citywide version of MHA. Though the “citywide” name makes it sound like all of Seattle is about to be upzoned, the new policy affects 27 neighborhood urban villages, leaving much of the city untouched.

Another misperception is that MHA is a uniform upzone that will allow high rises throughout Seattle. Each neighborhood is getting a variety of changes, depending on existing zoning. In many cases, each zone is essentially getting one notch denser.

For example, in the Rainier Beach neighborhood along Rainier Avenue, neighborhood commercial zones are changing from a maximum building height of 40 feet to 55 feet. At Jackson Street and 20th Avenue in the Central District, commercial buildings can now be 75 feet instead of 65 feet. Existing low-rise zones that allow duplexes, triplexes and small apartment buildings will get denser, as well. In Low Rise 2 zones, backyard cottages can be up to 22 feet high instead of the current 18 feet, and apartment buildings can be four stories instead of three.