Property Line Changes

See also: Land Use / Master Use Permit - Plat

What Is It?

A black man thinking about changing property lines between two buildings.A property line change involves moving the property boundary between your property and the property next to yours. For instance, property owners may want to move the property line of a lot with a single-family house on it. This process is called a lot boundary adjustment, or an LBA.

You may want to move your property line to:

  • Include a building, such as your garage, that does not fully lie on your property
  • Resolve a boundary disagreement between you and another property owner
  • Adjust existing lots so each are big enough to build on separately

You may not create a new lot by moving your property line.

What Permits Do You Need?

You need a lot boundary adjustment permit to make changes to your property line. You can find more information about this permit, including a detailed customer Tip and how to apply on our Land Use / Master Use Permit - Plat webpage.

Research the Code

You application will need to show us that moving your property line will still maintain lots that conform to our land use code in the Seattle Municipal Code (SMC) and our building codes. Our customer Tip 213B, Lot Boundary Adjustments, has additional information about the requirements, process, and our review. For the complete criteria of approval for the LBA, please consult the land use code (SMC 23.28).

If your property is in a neighborhood residential zone (residential small lot (RSL), neighborhood residential NR3, NR2, or NR1), you need to follow the rules listed below. For complete requirements, consult the land use code (SMC 23.44)

If your lot is in zone other than neighborhood residential, we may have different rules for you to follow; consult our land use code or ask our land use planners.

Minimum lot size. The minimum lot size depends on which neighborhood residential zone your house is located in. Additionally, the adjusted lot width and lot area can affect the height of the structure.

Minimum density. In neighborhood residential zones that have a residential small lot (RSL) designation, the lot must meet the density, and have enough lot area to support the number of dwelling units.

Lot coverage and floor area ratio. The amount of a lot area that can be covered by structures and the amount of gross floor area permitted on a lot depends on which neighborhood residential zone your house is located.

Minimum yards. Your neighborhood residential zoned house can’t be too close to the adjusted property line. Please review the yards section of SMC for more information.

Parking and access. Your neighborhood residential zoned lot must meet our rules for parking and car access to your property. Usually, we require you to maintain the property’s parking spaces and access to them. Most neighborhood residential zoned lots require at least one parking space per lot.

Regulations that govern environmentally critical areas. If your neighborhood residential zoned lot is in an environmentally critical area (ECA), you must have a topographic survey that delineates the area on a drawing when you apply for a lot boundary adjustment.

Utility service. Your neighborhood residential zoned lot must meet our minimum levels of service for water, sewer, power, and fire access.

Fire separation distances. If you’re moving your property line, the line’s new location should be at least 5 feet from your neighborhood residential zoned home, garage, and accessory buildings. In most cases, your buildings’ walls and eaves must be fire rated if they are less than 5 feet from your property line’s new location and openings located in these walls are limited.

  • Seattle Residential Code R302

Should You Hire a Professional?

In some cases, and if your site is not in an ECA, you may create them if you can develop scaled drawings with lot lines, bearings, right-of-way information, building and lot line dimensions, and location of all utility services and trees. See examples in the Lot Boundary Adjustment form.

If you are not able to complete the documents yourself, please hire a licensed surveyor. A licensed surveyor typically creates the documents for your lot boundary adjustment application. They can use our example of the Auto CAD drawing.

Construction and Inspections

Nathan Torgelson, Director
Address: 700 5th Ave, Suite 2000, Seattle, WA, 98104
Mailing Address: P.O. Box 34019, Seattle, WA, 98124-4019
Phone: (206) 684-8600
Phone Alt: Violation Complaint Line: (206) 615-0808
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SDCI issues land use, construction, and trade permits, conducts construction and housing-related inspections, ensures compliance with our codes, and regulates rental rules. SDCI is committed to an antiracist workplace and to addressing racism through our work in the community.