Growth Management Act. 
The Growth Management Act (GMA) is the State of Washington's comprehensive land use planning framework for counties and cities.  The GMA establishes land use designation and environmental protection requirements for all Washington counties and cities, 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.  Participating counties are required to designate urban growth areas (UGAs) within their boundaries sufficient to accommodate a 20-year population projection range to encourage urban growth.  

Affordable Housing Incentive Programs. 

Jurisdictions that fully plan under the GMA are authorized to enact or expand affordable housing incentive programs to provide for the development of low-income housing units through development regulations.  These programs may include provisions pertaining to:

• density bonuses within the UGA;
• height and bulk bonuses;
• fee waivers or exemptions;
• parking reductions; and
• expedited permitting.

Programs may be implemented through development regulations, conditions on rezoning or permit decisions, or both, on residential, commercial, industrial, and mixed-use development.

Affordable housing incentive programs enacted or expanded must comply with various requirements, including:

• providing for the development of low-income housing units;
• establishing standards for low-income renter or owner occupancy housing;
• establishing a maximum rent level or sales price for each low-income housing unit developed under the terms of a program; and
• committing low-income housing units developed under an affordable housing incentive program to continuing affordability for at least 50 years.

Tiny House Communities. 
A tiny house community is real property rented or held out for rent to others for the placement of tiny houses with wheels or tiny houses using the binding site plan method.  Cities and towns may adopt ordinances regulating the creation of tiny house communities, including through use of the binding site plan method, and may not prohibit the entry or require the removal of a tiny house with wheels used as a primary residence in a manufactured or mobile home community, with certain exceptions.  The landowner on which a tiny house community is located must make reasonable accommodation for utility hookups for water, power, and sewer services in compliance with the Manufactured/Mobile Home Landlord-Tenant Act (MHLTA).  Tenants of tiny house communities are entitled to all rights and subject to all duties and penalties under the MHLTA. 

The binding site plan method is an alternative process to the state subdivision law for creating parcels for sale or leases.

Tiny house communities may be part of an affordable housing incentive program.