Chapter 17.58


17.58.010    Purpose and intent.

17.58.020    Definition – Tiny house on wheels.

17.58.030    Design standards.

17.58.040    Accessory dwelling units.

17.58.050    Tiny house on wheels communities.

17.58.010 Purpose and intent.

The general purpose of this chapter on tiny houses on wheels and tiny house on wheels communities is to:

A. Permit tiny houses on wheels as accessory dwelling units under certain conditions in all residential districts where detached accessory dwelling units are allowed.

B. Permit tiny house on wheels communities in the C-II and C-II(S) districts, subject to the standards of those districts and those of PTMC 17.58.030 to ensure development of this type is generally compatible with surrounding uses.

C. Permit tiny houses on wheels as employer-provided housing per Chapter 17.64 PTMC. (Ord. 3306 § 1 (Exh. Z), 2023).

17.58.020 Definition – Tiny house on wheels.

A “tiny house on wheels” is a structure no larger than 400 square feet, excluding loft area space, intended for separate, independent living quarters, designed as a permanent, year-round residence for one household that meets these five conditions:

A. Is licensed and registered with the Department of Motor Vehicles and is constructed and certified to building and inspection standards in PTMC 17.58.030;

B. Is towable by a bumper hitch, frame-towing hitch, or fifth-wheel connection, and is not designed to move under its own power;

C. Is no larger than allowed for movement on public highways;

D. Has at least 150 square feet of first floor interior living space and unit does not exceed 16 feet in height;

E. Is a detached self-contained unit which includes basic functional areas that support normal daily routines including cooking, sleeping, and sanitation. (Ord. 3306 § 1 (Exh. Z), 2023).

17.58.030 Design standards.

A. Tiny houses on wheels must be built to meet requirements of American National Standards Institute (ANSI) Standard A119.5. Such standards shall include standards for the installation of heating, electrical systems and fire and life safety. In addition, tiny houses on wheels must meet these standards:

1. Insulation to a minimum of R-13 in walls and floors and R-19 in ceiling;

2. Residential-grade insulated doors and windows, with windows to be at minimum double-pane and of tempered or laminated safety glazing;

3. Full trim surrounds for all exterior windows and doors;

4. Roof pitch of at least 2:12;

5. Roofing materials of 20-year asphalt composite shingle or better, minimum Class A;

6. Electrical system that meets NFPA 70 NEC, Section 551 or 552 as applicable;

7. Low voltage electrical systems meet the requirements of ANSI/RVIA Low Voltage Standard, current edition;

8. Wall framing studs are 24 inches on center maximum, with a minimum of two by four wood or metal studs or equivalent SIP panels; and

9. Mechanical equipment shall be incorporated into the structure and not located on the roof.

B. Certification. Tiny houses on wheels shall be inspected and certified for compliance with the additional requirements in this chapter and ANSI 119.5 standards as follows:

1. Under RCW 43.22.355 for compliance with ANSI 119.5 standards; and

2. By a licensed Washington State design professional, architect or engineer for compliance with design standards of this section.

C. Utilities. Tiny houses on wheels shall be connected to municipal utilities as required by city and state law.

D. Foundation. Tiny houses on wheels shall incorporate the following foundation elements:

1. The undercarriage (wheels, axles, tongue and hitch) shall be hidden from view with fire retardant skirting surrounding the entire unit.

2. The wheels and leveling or support jacks must sit on a paving surface such as concrete or decomposed granite sufficient to hold the weight of the unit on wheels and jacks. (Ord. 3306 § 1 (Exh. Z), 2023).

17.58.040 Accessory dwelling units.

As of July 1, 2023, tiny houses on wheels are permitted as accessory dwelling units in R-I, R-II, and R-III districts subject to the provisions of PTMC 17.16.020 and the requirements below:

A. Review. Tiny houses on wheels shall be subject to a Type I review.

B. Entry. To meet egress requirements, a front porch approved by the city is required.

C. Separation. A tiny house on wheels shall be located at a fire separation distance of at least 10 feet from any other structures on the premises.

D. Appearance. To maintain the character of residential areas, a tiny house on wheels shall be designed to look like a conventional residential structure rather than a recreational vehicle. This shall be done by incorporating design features and materials typically used for houses, such as typical siding or roofing materials, pitched roofs, or residential windows.

E. Addressing. All tiny houses on wheels must obtain separate address approval from the city for the unit.

F. Utility Connection. A tiny house on wheels must have a permitted and permanent connection to all applicable municipal utilities. (Ord. 3306 § 1 (Exh. Z), 2023).

17.58.050 Tiny house on wheels communities.

As of July 1, 2023, tiny house on wheels communities permits may be authorized in concert with a binding site plan or a unit lot subdivision that meets the following requirements:

A. Intensity. There shall be a minimum of four tiny houses and maximum of 12 tiny houses per tiny house on wheels community.

B. Location. Tiny house on wheels communities shall be set back a minimum of 50 feet from an arterial frontage in the C-II and C-II(S) zone.

C. Centralized Common Area. The common open space area shall include usable public spaces such as lawns, gardens, patios, plazas or scenic viewing areas, with all houses having access to it.

1. Two hundred square feet of usable common open space is required per unit.

2. Fifty percent of units shall have their main entry on the common open space.

3. Setbacks shall not be counted towards the usable common open space calculation.

4. The usable common open space shall be located centrally to the tiny house on wheels community.

5. Community buildings or clubhouses may be counted towards the common open space calculation.

6. Tiny houses shall surround the common open space on a minimum of two sides.

7. Common open space shall be located outside of stormwater/detention ponds, wetlands, streams, lakes, and critical area buffers, and cannot be located on slopes greater than 10 percent.

D. Standards. Tiny house on wheels communities shall comply with applicable bulk, dimensional, and density requirements for the district(s) in which they are located in addition to the standards below:

1. The minimum lot area per dwelling unit shall be 1,250 square feet. In no case shall the project exceed the base density of the underlying zone.

2. The maximum lot area per dwelling unit shall be 3,000 square feet.

3. The maximum lot coverage shall not exceed 40 percent.

4. Perimeter setbacks shall be no less than 10 feet along all exterior property lines.

5. Tiny houses and porches shall be set back no less than five feet from the usable common open space.

6. No structure or portion thereof shall be closer than five feet to any neighboring structure.

7. Maintenance of Open Space and Utilities. Before approval is granted, the applicant shall submit covenants, deeds and homeowners’ association bylaws or other documents guaranteeing maintenance and common fee ownership of public open space, community facilities, private roads and drives, and all other commonly owned and operated property. These documents shall be reviewed and accompanied by a certificate from an attorney that they comply with the requirements of this chapter prior to approval. Such documents and conveyances shall be accomplished and be recorded, as applicable, with the county auditor as a condition precedent to the granting of occupancy or the filing of any final plat of the property or division thereof, except that the conveyance of land to a homeowners’ association may be recorded simultaneously with the filing of a final plat.

8. Tiny houses on wheels (THOW) in tiny house on wheels communities must comply with the following:

a. THOWs shall be placed in a designated area in the approved site plan of the pocket neighborhood.

b. At least 50 percent of the units shall abut a common open space, and all of the units shall be within 60 feet walking distance, measured from the nearest entrance of the unit, along the shortest safe walking route to the nearest point of the common open space.

9. All THOWs shall meet the tie-down and skirting requirements of the applicable building codes. The building official may require additional standards to ensure the porches hide any hitches.

10. Applications for tiny house on wheels communities shall be processed according to Type III review. (Ord. 3306 § 1 (Exh. Z), 2023).