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 lot with a single-family house on it. This process is called lot boundary adjustments, or 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 cannot 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 rules 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, please consult the land use code (SMC 23.28).

If your property is in a neighborhood residential zone (Neighborhood Residential Small Lot (RSL), NR3, NR2, or NR1), you need to follow the rules 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 in.

Minimum density. In neighborhood residential zones that have a Neighborhood Residential Small Lot (RSL) designation, the lot must have enough area to support the number of dwelling units on the lot.

Lot coverage and floor area ratio. The amount of a lot 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 in.

Minimum yards. Your single-family house can’t be too close to the property line.

Parking and access. Your neighborhood residential 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 lot is in an environmentally critical area, you must have a survey that delineates the area on a drawing when you apply for a lot boundary adjustment. We may have other requirements.

Utility service. Your neighborhood residential 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 single-family home, garage, and related 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?

A licensed surveyor usually creates the documents for your lot boundary adjustment application. In some cases, and if your site is not in an environmentally critical area, 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.