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Legislature Paves the Way for Tiny Houses

Legislature Paves the Way for Tiny Houses

Living in tiny houses (also called tiny homes) is both an increasingly attractive and affordable housing option as well as a trending alternative lifestyle choice. However, because of significant regulatory barriers, this housing option has not yet gained traction in Washington State. This should hopefully change with the passage of ESSB 5383—a bill intended to enable the development of tiny house villages or communities throughout the state.


Some of the perplexing questions associated with regulating tiny houses have been:

What are they?

Are they recreational vehicles? Are they mobile homes? Are they site-built structures? Unfortunately, tiny houses don’t often fit neatly into any of these categories. Some tiny houses are on wheels; some are built on permanent foundations. Many are the manifestation of creative DIYers and defy categorization.

Depending on their characteristics, a different regulatory structure might apply. For example, recreational vehicles (RVs) must be certified with the Department of Labor and Industries (L&I). However, the certification process has historically been challenging and not suited to a custom-built RV or a tiny house on wheels. (Note, however, there is now a self-directed process available that makes it easier for custom RVs/tiny houses on wheels to obtain certification from L&I.)

Site-built structures, on the other hand, must comply with the local building codes. Tiny houses typically have not been able to meet both the size and technical specifications for single-family dwellings in local building codes.

Where can they go and how long can they stay?

If a tiny house is on wheels, local jurisdictions typically will look at this as an RV. Unless sited in a mobile-home/RV park or some other limited exception in a local zoning code applies (e.g., RV used as a caretaker’s residence), RVs may not typically be used as permanent residences.

If a tiny house is to be built on a foundation, the greatest obstacles relate to complying with the building codes (as noted above). However, local zoning and development regulations also present challenges, such as minimum size and parking requirements. Further, occupancy limits and limits on numbers of accessory dwellings on residential lots limit the potential for community living.

For a deeper dive into the regulatory challenges associated with tiny houses, take a look at this MRSC Insight blog post and Legalizing the Tiny House from Sightline Institute. 

What Does the New Legislation Do?

ESSB 5383 supports the development of tiny houses in several ways, as outlined in this section.

Defines tiny houses

The new legislation defines “tiny houses” and “tiny houses with wheels” as:

a dwelling to be used as permanent housing with permanent provisions for living, sleeping, eating, cooking, and sanitation built in accordance with the state building code.

This distinguishes tiny houses from recreational vehicles and other types of housing, so that these structures can be regulated in their own category and used as permanent residences.

Directs adoption of building code standards for tiny houses

In 2018, the International Code Council issued tiny house building standards in Appendix Q of the International Residential Code (IRC). ESSB 5383 directs the State Building Council to adopt standards specific to tiny houses by December 31, 2019. The legislature expects the newly-issued IRC guidance to become the basis for these standards. Local governments, in turn, can amend their building codes to include these new provisions.

Also, just last year the state legislature passed a bill authorizing local governments to adopt regulations eliminating any minimum gross floor area requirements for single-family dwellings (See HB 1085).

Includes prefabricated tiny houses in definition of factory-built housing

The bill expands the definition of factory-built housing in RCW 43.22.450 to include tiny houses and tiny houses with wheels, thereby incorporating prefabricated tiny houses into the L&I certification process for factory-built housing.

Creates a regulatory pathway for permitting tiny house communities

Currently RCW 58.17.040(5) allows the use of a binding site plan:

for the purpose of lease when no residential structure other than mobile homes or travel trailers are permitted to be placed upon the land.

ESSB 5383 expands this section of the subdivision statute to include tiny houses and tiny houses with wheels, thus allowing the use of a local binding site plan process to create tiny house communities or villages. In addition, a new section is added to Chapter 35.21 RCW that will allow a city or town to adopt an ordinance to regulate the creation of tiny house communities.

The bill also amends RCW 35.21.684(3) to prohibit cities or towns from adopting ordinances that would prevent tiny houses with wheels from being used as a primary residence within manufactured/mobile home communities. However, a local government may require that the tiny houses contain at least one internal toilet and shower or that the mobile home community provide such toilets and showers.

Extends protections under Manufactured/Mobile Home Landlord-Tenant Act (MHLTA)

The legislation extends protections of Chapter 59.20 RCW to tenants of tiny house communities. The Northwest Justice Project offers a summary of a tenant’s rights and obligations under the MHLTA.

Waives competitive bidding requirements for construction of tiny houses by students 

School districts, higher-education institutions, and other government entities that offer eligible training programs for students can contract with community organizations, nonprofits, and others to build tiny houses for low-income housing, without regard to competitive bidding requirements.

Next Steps for Local Governments

Local governments interested in expanding opportunities for use of tiny houses can start the planning process for adopting local regulations consistent with the new legislation. These actions could include:

  • Forming stakeholder advisory committees and encouraging community engagement.
  • Reviewing zoning maps and comprehensive plans to determine where tiny house communities could be located.
  • Identifying existing barriers to tiny houses in code (e.g., minimum size requirements).
  • Amending binding site plan regulations to include tiny houses and tiny houses with wheels.
  • Amending the local building code to incorporate new state standards for tiny houses (once adopted later this year).
  • Drafting regulations for siting tiny house communities.

Resources and Further Reading

As part of its Missing Middle Housing initiative, the City of Olympia developed white pages on current conditions for tiny houses, as well as recommended policy changes in the areas listed below to encourage the construction of tiny homes, duplexes, triplexes, and fourplexes.

MRSC is a private nonprofit organization serving local governments in Washington State. Eligible government agencies in Washington State may use our free, one-on-one Ask MRSC service to get answers to legal, policy, or financial questions.

Photo of Jill Dvorkin

About Jill Dvorkin

Jill joined MRSC as a legal consultant in June 2016 after working for nine years as a civil deputy prosecuting attorney for Skagit County. At Skagit County, Jill advised the planning department on a wide variety of issues including permit processing and appeals, Growth Management Act (GMA) compliance, code enforcement, SEPA, legislative process, and public records. Jill was born and raised in Fargo, ND, then moved to Bellingham to attend college and experience a new part of the country (and mountains!). She earned a B.A. in Environmental Policy and Planning from Western Washington University and graduated with a J.D. from the University of Washington School of Law in 2003.