Rules on Single-Family Housing in Seattle, Washington

Household Size and Home-Based Businesses

• In Seattle, one household in a single-family zone can consist of up to eight unrelated people or any number of related people. A business can be run from the home as long as it's clear that the principal use of the dwelling is residential. The business can't impact on the appearance of the house; deliveries and signage are restricted. Certain businesses, such as bed and breakfasts and animal care, have separate regulations from other enterprises.

Residential, Single-Family Zones

• There are three types of residential single-family zones defined in the Seattle Municipal Code. They vary by the minimum lot size required for each structure. There is also a residential small-lot zone, allowing a smaller lot size than the others, to encourage affordable housing. Each zone permits a single dwelling unit, or one single-family unit and one additional dwelling unit attached to the same structure. Since 2009 the City of Seattle also allows detached backyard cottages, sometimes known as mother-in-law units, in single-family zones, except for lots in the shoreline district.

Height Limits

• In Seattle, the height of homes in the single-family zone is set according to the lot width. For lots wider than 30 feet, the maximum height allowed is 30 feet. For lots 30 feet or less, the height is 25 feet. If the neighboring houses are higher, the heights can be set to the average in the neighborhood, capped at 30 feet for lots 30 feet wide or less. Heights can be increased up to five feet more if the lot is sloping.

Lot Coverage and Yard Requirements

• In Seattle, homes in single-family residential zones cannot cover more than 35 percent of the lot. There is no limit on lot coverage for the residential small-lot zone. For the single-family zones, the dwelling has to be five feet from the property line on the side and 20 feet from the front property line, unless the neighboring properties have smaller front yards. Also, the rear yard must have 20 percent of the lot depth, or a minimum of a 10-foot setback from the rear property line.

Seattle Municipal Code

• Single-family residential zones in Seattle don't have design review or open space and landscaping requirements. However, some other residential land uses are regulated by the Seattle Municipal Code, such as parking, garages, accessory structures and additions, and fences. Zoning can change with some frequency, so consult the code when considering alterations to your home.