Subdivisions

Overview

The subdivision of land into lots is governed in Washington State by chapter 58.17 RCW and by city and county ordinances adopted under that chapter's authority. The following is a list of key terms used in the subdivision statutes.

• Subdivisions are defined in RCW 58.17.020(17) as the "division or redivision of land into five or more lots, tracts, or parcels, sites, or divisions for the purpose of sale, lease, or transfer of ownership."
• Short subdivisions are defined in RCW 58.17.020(16) as the "division or redivision of land into four or fewer lots, tracts, parcels, sites, or divisions for the purpose of sale, lease, or transfer of ownership." Any city or town may increase the number of lots that can be regulated as short subdivisions up to a maximum of nine. Counties planning under the Growth Management Act may do the same with respect to unincorporated land within an urban growth area.
• Plats and short plats are defined in RCW 58.17.020(13) and (15) as the maps or representations of subdivisions and short subdivisions, respectively, that show the division of land into lots and streets, alleys, dedications, easements, etc.
• A Binding Site Plan is an alternative method of land division authorized by RCW 58.17.035. For more information, see Site Plans and Binding Site Plans or Exemptions section below.
• Unit lot subdivision refers to the division of a parent lot into separately owned “unit lots.” Local governments must provide for this type of division in their short plat regulations pursuant to RCW 58.17.060(3).

Exemptions

Certain land divisions are exempt from state subdivision laws. See RCW 58.17.040.

These exempt divisions include:

• Burial plots.
• Divisions into lots above a certain size.
• Divisions "made by testamentary provisions, or the laws of descent."
• Boundary line adjustments (no additional lots created).
• Divisions for industrial or commercial use when a binding site plan is approved.
• Divisions for leasing lots for mobile homes when a binding site plan is approved.
• Divisions where a portion of the property is developed as a condominium (and certain other requirements, including a binding site plan, are met).

RCW 58.17.035 authorizes cities and counties to, by ordinance, establish procedures for use of binding site plans as an alternative to the subdivision process for the divisions identified in RCW 58.17.040 that require approval of a binding site plan to be exempt.

Subdivision Process Overview

Subdivisions, other than short subdivisions, must be regulated by cities and counties according to the procedures in chapter 58.17 RCW.

These statutory procedures establish a two-step process for the approval of subdivisions:

1. Preliminary plat approval.
2. Final plat approval.

Note that both subdivision and short subdivision approval require compliance with local ordinances such as those dealing with zoning, road standards, shorelines, utilities, and drainage, as set out by RCW 58.17.110.

Preliminary Plats

Initial Review and Hearing

Preliminary plat review is generally a quasi-judicial process that involves an initial review and public hearing by the city or county planning commission or agency, which then makes a recommendation to the city council or board of county commissioners (RCW 58.17.070 - 58.17.090). A city or county may designate a hearing examiner as an alternative to a planning commission or agency hearing and issuing recommendations for preliminary plat approval (RCW 58.17.330). For a definition of quasi-judicial land use actions, see RCW 42.36.010.

As an alternative to the hearing/recommendation process, a city or county may, by ordinance, authorize administrative review of preliminary plats without a public hearing (RCW 58.17.095). The ordinance may specify a threshold number of lots in a subdivision above which a public hearing must be held, and may specify other factors which necessitate the holding of a public hearing. A notice of application must be made, and if a member of the public or the governing body of the city or county requests a public hearing within 21 days of receiving notice of application, a public hearing shall be held. 

Requirements for Approval

Unless the applicant requests otherwise, a preliminary plat must be processed simultaneously with applications for accompanying rezones, variances, planned unit developments, site plan approvals, and similar quasi-judicial or administrative actions to the extent that the procedural requirements for those actions allow for simultaneous processing.

A city or county may not approve a preliminary plat unless the city council, board of county commissioners or county council, or hearing examiner, as the case may be, make written findings regarding certain matters identified in RCW 58.17.110, including open spaces, drainage ways, streets or roads, alleys, other public ways, transit stops, potable water supplies, sanitary wastes, parks and recreation, and playgrounds. Cities must ensure that regulations and conditions for plat approval are consistent with the minimum density requirements in RCW 36.70A.635. Cities and counties must ensure their regulations and conditions for approval are consistent with requirements for allowing accessory dwelling units in RCW 36.70A.680, .681, and .699.

Time Limitations for Approval

Preliminary plats must be approved, disapproved, or returned to the applicant for modification within 90 days of the filing of the preliminary plat application, unless the applicant consents to an extension. This does not include time preparing environmental impact statements. See RCW 58.17.140.

Final Plats

Time Limitations for Submission

RCW 58.17.140 sets out the rules regarding the time period for an applicant to submit a preliminary plat for final plat approval. The general rule is that the applicant has five years after preliminary plat approval in which to submit the plat for final approval. However:

• If the preliminary plat was approved before January 1, 2015, the applicant has seven years to submit a final plat. 
• If a preliminary plat was approved before January 1, 2008 and is not subject to the Shoreline Management Act, the applicant has 10 years to file for final plat approval.

Also, a city or county may adopt procedures by ordinance for extensions of these time periods. For examples, see Examples of Subdivisions City and County Codes section.

Approval Process

Final plat approval must be made by the legislative body, or the legislative body may delegate that authority to “an established planning commission or agency, or to such other administrative personnel in accordance with state law or local charter” by ordinance (RCW 58.17.100). The final plat approval is in the nature of a ministerial, non-discretionary process; that is, if the applicant meets the terms of preliminary approval and the plan conforms with state law and local ordinances, final approval must be granted (RCW 58.17.170). There is no public hearing for a final plat approval.

Examples of Ordinances Allowing Administrative Final Plat Approval

Below are ordinances from various Washington jurisdictions amending their municipal code to allow an administrative body or personnel to approve final subdivision plats.

• Auburn Ordinance No. 6654 (2017) – Allows final plat approval by the Planning and Development Department Director.
• Spokane County Ordinance No. 2017-1041 (2018) – Allows final plat approval to be delegated administratively.
• Yakima Ordinance No. 2017-030 (2017) – Allows the Community Development Director, rather than the city council, to approve final subdivision plats.

Requirements for Approval

Among the statutory requirements for final plat approval are:

• Recommendation for approval by the local health department or the agency that would be furnishing sewer and water;
• Approval by the city or county engineer;
• A complete survey; and
• Certification that all taxes and delinquent assessments for the property have been paid.

See RCW 58.17.150, RCW 58.17.160, and RCW 58.17.165.

Time Limitations for Approval

Final plats must be approved, disapproved, or returned to the applicant for modification within 30 days of filing, unless the applicant consents to an extension. See RCW 58.17.140.

Recording and Filing Requirements

Lots in a subdivision cannot be sold until final plat approval is obtained and the plat is recorded with the county auditor. See RCW 58.17.195.

If the county assessor has adopted an "assessor's plat" for the county, before filing with the county auditor, approved final plats must be submitted to the county assessor for "the sole purpose of assignment of parcel, tract, block and or lot numbers." See RCW 58.18.010.

Period of Validity

RCW 58.17.170(3) sets out the period of validity for an approved final plat. The lots in an approved final plat are "a valid land use notwithstanding any change in zoning laws" for a period of five years from final plat approval. See RCW 58.17.170(3)(a).

• If the final plat was approved before January 1, 2015, the vesting period is seven years.
• If the final plat was approved before January 1, 2008, it is vested for a period of 10 years from final plat approval.

Also, approved final plats are vested with respect to the conditions of plat approval and with respect to applicable laws for these same time periods, except when "a change in conditions creates a serious threat to the public health or safety in the subdivision." Though, for final plats approved before January 1, 2008, the 10-year vesting period with respect to the conditions of plat approval and to applicable laws applies only if the plat is not within Shoreline Management Act jurisdiction. See RCW 58.17.170(3)(b).

Note that these vesting limitations in RCW 58.17.170(3) do not apply to short plats, which have no vesting limitations. See Noble Manor v. Pierce County (1997).

Short Subdivision Process

No process is set out in state law for approval of short plats. Cities and counties are required by RCW 58.17.060 to adopt by ordinance their own regulations and procedures that provide for "summary approval" of short plats through an administrative process. Regulations and conditions for approval must be consistent with the minimum density requirements in RCW 36.70A.635 and the requirements for allowing accessory dwelling units in RCW 36.70A.680, .681, and .699. 

In 2023, RCW 58.17.060 was amended to require that unit lot subdivisions be included in short plat regulations for all Washington cities, towns, and counties. RCW 58.17.060(3) states: 

All cities, towns, and counties shall include in their short plat regulations procedures for unit lot subdivisions allowing division of a parent lot into separately owned unit lots. Portions of the parent lot not subdivided for individual unit lots shall be owned in common by the owners of the individual unit lots, or by a homeowners’ association comprised of the owners of the individual unit lots.

For more information about unit lot subdivisions and examples of ordinances, see the Unit Lot Subdivision section below. 

Approval Process

Because it must be an administrative process, there is no public hearing for a short plat application, and the legislative body is not involved in the process. To approve a short plat, the administrative personnel assigned to review short plat applications must make the same written findings in RCW 58.17.110 that are required for subdivision (plat) applications.

Time Limitations for Approval

Short plats must be approved, disapproved, or returned to the applicant for modification within 30 days of the filing of the short plat application, unless the applicant consents to an extension. See RCW 58.17.140.

Recording and Filing Requirements

They must be filed with the county auditor and are not deemed "approved" until such filing. See RCW 58.17.065.

Period of Validity

There is no limitation on the period of validity of an approved short plat as there exists with respect to approved final plats. See Noble Manor v. Pierce County (1997).

Unit Lot Subdivisions

Unit lot subdivisions are a method of dividing a single parent parcel into individual “unit lots” that may be sold to individual owners. In a unit lot subdivision, the parent parcel must conform to zoning dimensional standards while individual “unit lots” do not. A unit lot subdivision could be utilized where multi-family or middle housing (e.g., duplex, triplex, townhomes, cottage housing) development is allowed, as well as where accessory dwelling units are developed on a lot with a single family residence. Unit lot subdivisions are not intended to permit land uses or densities that are not otherwise allowed in the zone in which a unit lot subdivision is proposed. 

In 2023, the legislature added a requirement for local governments to adopt unit lot subdivision provisions into their short subdivision regulations. In 2025, the legislature clarified that only cities and towns located in counties that are planning under the Growth Management Act (GMA), RCW 36.70A.040, must adopt the new unit lot subdivision regulations. See RCW 58.17.060(3). 

The 2025 amendments to RCW 58.17.060(3) added new requirements and limitations that must be incorporated into local unit lot subdivision regulations. These include:

• Procedures requiring that “prominent informational notes” be placed on the unit lot subdivision’s plat prior to recording.
• Limitations on predecision meetings and hearings, except as required by state law.
• Limitations on design review.
• Notice to property owners within 250 feet of a proposed unit lot subdivision.

The Department of Commerce has developed a Unit Lot Subdivisions Fact Sheet (2025) with information about the new requirements for unit lot subdivisions within city and town short subdivision regulations. The fact sheet is intended to provide information and recommendations for jurisdictions to consider in adopting code that implements RCW 58.17.060(3).

The following are some examples of unit lot subdivision regulations (adopted prior to 2025 legislation):

• Bellevue Municipal Code Sec. 20.45A.065 – Special Requirements for Unit Lot Subdivisions.
• Lake Stevens Municipal Code Sec. 14.18.320 – Unit Lot Subdivisions.
• Lynnwood Municipal Code Ch. 19.40 – Fee Simple Unit Lot Subdivisions.
• Mountlake Terrace Municipal Code Ch. 17.09 – Fee Simple Unit Lot Subdivisions.
• Redmond Municipal Code Sec. 20D.180.10 – Subdivision and Short Subdivision Regulations. See Section 20D.180.10-060(6) which specifically addresses unit lot subdivisions.
• Renton Municipal Code Sec. 4.7.090 – Unit Lot Subdivisions.

Administrative Residential Lot Splitting

Pursuant to RCW 58.17.145, local governments must include provisions to allow a single residential lot to be split into two through an administrative review. The split must meet specific standards, such as zoning, access, utilities, and lot size. If all conditions are met, approval is required, but no additional splits are allowed from the same lot under this provision. The intent is to create a more streamlined process for homeowners, providing them options while also encouraging the development of middle housing.

Local ordinances adopting new lot splitting provisions are exempt from SEPA administrative or judicial appeal under chapter 43.21C RCW.

Examples of Subdivisions City and County Codes

The following codes exemplify how a range of jurisdictions in Washington State have implemented state subdivision law.

City Examples

• Bothell Municipal Code Title 15
• Brewster Municipal Code Title 16
• College Place Municipal Code Title 14.90
• Ferndale Municipal Code Title 17

County Examples

• King County Code Title 19A
• San Juan County Code Ch. 18.70
• Whatcom County Code Title 21
• Yakima County Code Ch. 19.34

Recommended Resources

• Washington State Department of Commerce: A Short Course on Local Planning Resource Manual (2017) – See section on the platting process.