Growth Management Act.

The Growth Management Act (GMA) is the state's comprehensive land use planning framework for counties and cities.  The GMA establishes land use designation and environmental protection requirements for all counties and cities within the State of Washington, and a significantly wider array of planning duties for counties and the cities within that are obligated by population-based criteria or choice to satisfy all planning requirements of the GMA.

Urban Growth Areas.

Under the GMA, participating counties are required to designate urban growth areas (UGA) within their boundaries sufficient to accommodate a 20-year population projection range provided by the Office of Financial Management.  Each city located within a planning county must be included within a UGA.  Urban growth must be encouraged within the UGAs, and only growth that is not urban in nature can occur outside of the UGAs.  Each UGA must permit urban densities and include greenbelt and open space areas.

Average Minimum Density Requirements.

Floor area ratio is the measurement of a building's floor area in relation to the size of the lot or parcel on which the building is located.  Minimum density specifies a minimum size, or floor area ratio, for new development. 

Middle Housing Requirements.

Any city with a population of 20,000 or more that plans under the GMA must authorize the development of all middle housing types on all lots zoned for detached single-family residential use and within one-half mile of a major transit stop.  These cities must also allow development of duplexes, triplexes, and fourplexes on all other lots zone for single-family residential use. 

Alternatively, cities may alter local zoning as follows:

• any city with a population of 500,000 or may allow an average minimum density equivalent to 40 dwelling units or more per gross acre across the entirety of the city's urban growth area (UGA);
• any city with a population between 100,000 and 500,000 may allow an average minimum density equivalent to 30 dwelling units or more per gross acre across the entirety of the city's UGA; and
• any city with a population between 20,000 and 100,000 may allow an average minimum density equivalent to 25 or more per gross acre across the entirety of the city's UGA.

Cities required to provide authorization for the development of all middle housing types that have not adopted local antidisplacement measures as a portion of the city's comprehensive plan housing element must, within nine months of the act's effective date,

• identify local policies and regulations that result in racially disparate impacts, displacement, and exclusion in housing;
• identify and implement policies and regulations to address and begin to undo racially disparate impacts, displacement, and exclusion in housing caused by local policies, plans, and actions; 
• identify areas that may be at higher risk of displacement from market forces that occur with changes to zoning development regulations and capital investments; and 
• establish antidisplacement policies, with consideration given to the preservation of historical and cultural communities as well as investments in low, very low, extremely low, and moderate-income housing, equitable development initiatives, inclusionary zoning, community planning requirements, tenant protections, land disposition policies, and consideration of land that may be used for affordable housing.

A city with a population of 10,000 or more that plans under the GMA must authorize the development of duplexes on all lots zoned for single-family residential use.  In addition to duplexes, cities may allow other middle housing types.

Alternatively, cities with a population between 10,000 and 20,000 may alter local zoning to allow an average minimum density equivalent to 15 dwelling units or more per gross acre.

Cities choosing to adopt an average minimum density must also adopt findings of fact demonstrating that actions taken to implement the average minimum density will not result in racially disparate impacts, displacement, or further exclusion in housing and shall transmit the findings to the Department of Commerce (Commerce). 

Cities may adopt development and design standards related to siting and design of middle housing but may not discourage the development of middle housing through fees, delays, or other requirements that make placing middle housing impracticable.  Cities may not implement or require processes stricter than those applied to detached single-family residences.  Cities may not require certain off-street parking requirements under various circumstances. 

For cities with a population over 10,000, the requirements take effect two years after the effective date of the act or one year after a determination by the Office of Financial Management that a city has reached a population threshold established under the act.

Technical Assistance.

The Commerce must provide technical assistance prioritized based on need to cities in implementing middle housing and average minimum density requirements.  The Commerce must develop and publish model middle housing ordinances within 18 months after the act takes effect.  The model ordinances supersede, preempt, and invalidate local development regulations that fail to allow middle housing within the time frames provided.  The Commerce must establish a process cities to seek approval of required local actions, and any local actions approved by Commerce are exempt from appeals under the GMA and the State Environmental Policy Act (SEPA).

Extensions.

Cities may apply for extensions of the timelines established.  Extensions may only be applied to specific areas where a city has identified water, sewer, stormwater, or transportation services that are deficient or will become deficient within five years and for which the city has established a plan of action to remedy such services on a specific timeline.

Amendments to development regulations and other actions taken by a city to implement the middle housing or average minimum density are not subject to administrative or judicial appeal under SEPA.