Effective Date Nov. 1st, 2020

Written by Janet Thome

Washington state has adopted  Appendix Q Tiny Houses, with amendments. The effective date is Nov. 1st, 2020. Appendix Q Tiny Houses was adopted into the 2018 International Residential Code ( IRC ) building code to provide regulations and standards for tiny homes on a foundation that is 400 square feet or less.

Attention is specifically paid to features such as compact stairs, including hand rails and headroom, ladders, reduced ceiling heights in lofts and guard and emergency escape and rescue opening requirements of lofts.

The International Residential Code is a comprehensive, stand alone residential code that creates minimum regulations for one-and two family dwellings of three stories or less.

Tiny House Bill 5383

Tiny House Bill 5383, which became effective on July 28th, 2019  defines tiny homes and mandated that the building code council write building codes for tiny homes. Washington state has adopted Appendix Q Tiny Houses which relates to tiny homes on a foundation.

Tiny Homes On Wheels

Tiny homes on wheels will go through the Modular inspection and approval process with L & i. This includes out of state manufacturers that sell to a consumer in Washington state.

Tiny Home Definition: Section Five HB 5383

“Tiny house” and “tiny house with wheels” means 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.

Washington state does not use 3rd party inspection agencies to inspect and certify. Please refer to Washington state Department Of Labor Of Industries ( L& I ) for the inspection and the approval process.

Reciprocal Agreements  States For Inspections

L & I has reciprocal agreements with Idaho and Oregon, where they inspect modular buildings built in Washington to their plans, and those states do the same in their states for their plans.

Please contact L & I, if you are building in another state besides Idaho and Oregon, to discuss the process for approval and inspection. It will require for L & I to travel to your location for inspection.

Washington State Department Of Labor And Industries: Attention Washington Residents

The Following Sourced From The Washington State Department Of Labor And Industries’ Website

A tiny house is a dwelling that may be built on wheels and is no larger than 400 square feet, including a kitchen, bathroom, and sleeping/living area, and must be built to the Washington State Building Code. The approval process for a tiny house depends on where it’s built.

  • If you are building a tiny house on the site where it will be occupied and used, then you do not need to read any further: Contact your local building department. You may also need an L&I electrical inspection.
  • If you’re building a structure with wheels, that’s not a tiny house as described above, then you may be building a recreational vehicle or park model. We inspect and regulate these units. You will need to contact your local building department to find out where it can be located or placed. See our bulletin for additional clarification on units L&I regulates.
  • If you’re purchasing a manufactured home of any size, including a tiny manufactured home, then you will need to contact your local building department to find out where it can be located.
  • If you’re building a tiny house somewhere OTHER than where it will be occupied and used, then see the Building a Tiny House tab.

Building A Tiny House

L&I is the building department for the construction of tiny houses that are built at offsite locations, such as a factory or even a back yard. L&I reviews plans and inspections for tiny houses built offsite from where they will be placed.

NOTE: The design of your tiny house must also meet local building department criteria. Contact your local building department for their requirements and permit information.

To get a tiny house approved:

First, Download and review the tiny house information packet. It includes the standards to which you need to design, plan, and build your tiny house.

We will need 3 copies of your plans. Plans must be stamped by a Washington professional engineer (PE) or architect.

Next, fill out these applications:

  • Tiny House Plan Approval & Insignia Request form (F623-039-000): This is your basic application and gets the insignia for the L&I inspector to place on your tiny house. The insignia is also important when talking with your local building department when you place the residence.
  • Notification to Local Enforcement Agency (F623-013-000): This is included with a copy of your plan that is sent to the local building department upon L&I approval.

Finally, include payment of $745.10 for plan review and insignia. We will notify you if we need more information or when your plans are approved

You can also submit your plans at your local L&I office, and pay the fee by cash, check, money order, or credit/debit card.

Because of the large number of requests, it can take several months for L&I to review plans. We will notify you if we need more information or if your plans have been approved.

Next, see the Do the Work tab.

Do The Work

Once plans for your tiny house are approved, you can start work.

Some important notes about licensing requirements:

When you build a tiny house there are several registration, and licensing issues you need to be aware of and consider.

  • You may need to be a registered general contractor depending where you are going to work on a tiny house, and what duties you are performing. Contact L&I’s contractors program to find out the requirements for your situation.
  • All plumbing must be installed by a Washington state licensed residential or commercial plumber.
  • All electrical work must be performed by a Washington State licensed electrical contractor and licensed electricians. You will need to get an L&I electrical permit to connect your house to power.

There are exceptions for homeowners doing electrical and plumbing work on their own house. Please contact L&I’s plumbing program and electrical program to determine the licensing requirements for your situation.

Note: Local building permits will be required for everything from the tiny houses foundation, installation, and its location on a property. Remember to contact your local building official for more information.

Next, see the Get Inspected tab

You will need to have your tiny house inspected several times by L&I as you complete certain stages of construction. You must contact us using either an in-state or out-of-state inspection request form before covering any work on the house. Our inspector will contact you to confirm an appointment.

When you need an inspection depends on when you complete the stages of construction shown on the form. This can include:

  • Floor
  • Plumbing
  • Electrical
  • Frame
  • Mechanical
  • Energy Code
  • Final

Be ready for the inspection. If you’ve requested an inspection and you’re not ready, you will still be charged. If the inspector must return to the location, you will be charged additional fees.

Structures that require permits

  • Modular buildings: Buildings which are constructed in factories and at other offsite locations and then shipped to Washington must be approved by L&I. This includes equipment shelters that can be entered by personnel.equipment shelters that can be entered by personnel.
  • Temporary Worker Housing (TWH): TWH units fabricated in factories and being shipped to Washington must be inspected by L&I as they are constructed.
  • Recreational vehicles and park models: All RVs and Park Model RVs for sale or lease in Washington must have an L&I approval label.
  • Commercial coaches: Commercial coach trailers must be inspected and approved by L&I.
  • See examples of labels for these structures.

Submit plans

Visit or mail the plans to the L&I office nearest you.

Contact Washington State Department Of Labor And Industries

1-800-705-1411 Option 3

Mailing address
Washington State Department of Labor & Industries
PO Box 44430
Olympia, WA 98504-4430

7273 Linderson Way SW
Tumwater, WA 98501


Attention: Both Washington State And Out Of State Builders : When submitting plans to L & I it is very important to send plans with the IRC and the Washington state amendments to Appendix Q Tiny Houses. The building code council moved some of the topics to within the body of the residential code.  Primarily regarding lofts.  Appendix Q also references the Washington State Energy Code.

WAC 51-51-60104

Photo Credit: Carriage Houses NW

Date For Adopted Changed Because Of Covid-19