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You are here:   Home → Built Environment → Planned Density
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Indicator: Planned Density

Data and Data Discussion provided by King County Benchmark Program

King County Urban Centers

Figure 2: Change in Achieved Densities, King County

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Upstream Indicators

There are currently no published Upstream Indicators.

Downstream Indicators
  •   Urbanization and Impervious Surface Changes --- The number of acres of urban land, clear-cut, and regenerating forest have increased in King County since 1986. Acres of grass and deciduous, mixed and coniferous forest have decreased. Acres of rural forests and privately owned working forests have declined in recent years  (view data graph)
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Related Goals

Planning for high density neighborhoods closer to urban centers can help to protect surrounding undeveloped land, limit resource acquisition, promote a pedestrian life-style, and increase economic growth within local communities.

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Sustainability Snapshot:

Over the years, urban sprawl has led to rural land consumption and a reduction in green space. Studies have documented that the environmental and economic costs associated with low density development is much higher than compact neighborhoods. There is also a significant link between health and sprawl - people living in places marked by sprawl are likely to walk less and weigh more. Planned density, through such policies as Washington’s Growth Management Act, can be an effective tool to achieve efficient land usage and avoid the negatives associated with fragmented development.

Sustainability Trend:

From 1996-2000 to 2002-2004, residential densities increased in King County. The 2004 density of 6.4 lots per acre for King County as a whole exceeds the benchmark of six lots per acre.

Data Discussion

The Indicator Defined

Achieved versus planned number of residential lots per acre, permitted single family units per acre and permitted multi-family units per acre.

Data Interpretation/Evaluation

Washington State’s Growth Management Act (GMA) requires King County to designate an Urban Growth Area (UGA), where future urban growth and development are to occur. Consistent with the GMA, the King County Countywide Planning Policies (CPPs) call for development to occur within the UGA to promote efficient use of land. Housing and employment growth is to be directed first to urban centers, then to areas already urbanized, and lastly to areas requiring major infrastructure improvements. The Urban Center strategy, whose goal is to attract employment and housing to the county’s urban centers, is an important element of the CPPs.

One way to monitor the efficient use of urban land is to measure how well we are achieving the densities in residential zones that our plans call for. Comparing achieved to planned densities is very useful at the jurisdictional level. However, planned densities vary greatly from zone to zone, and from city to city. At the sub-regional and County level it is more useful to compare average densities achieved currently to those achieved in the recent past.

Six dwelling units per acre is considered a benchmark of urban density for single family lots. Densities achieved in new subdivisions are a good predictor of the trend in single-family densities because the number and size of lots determines how many units per acre will eventually be built.

Throughout King County, 599 acres were divided into 3,848 new lots for single family homes in 2004. This corresponds to a density of 6.4 lots per acre and exceeds the benchmark of six lots per acre. (Figure 2) South King County and the rural cities increased density from 2003 with 6.6 lots per acre and 6.4 lots per acre respectively. Excluding the city of Seattle, the Sea-Shore sub-area created new lots for single family homes at the overall rate of 7.5 lots per acre. In 2004, the city of Shoreline recorded 24 lots on 2.9 acres. Initiated in 2002 and 2003, these lots were not recorded until 2004. This contributed to unusually low density in 2003 and high density in 2004. Only east King County did not improve its density from 2003 to 2004. However, it has made a marked improvement from the 1996-2000 period, increasing density from 3.9 single-family home lots to 6.2 lots per acre in 2004.

Throughout King County, densities achieved by new permits in single family zones have increased from 3.8 dwelling units (DU) per acre in the 1996-2000 period to 5.3 DU in 2004.

Multi-family unit densities decreased throughout the county from 2002, likely as a result of historical lows in mortgage interest rates. As home-ownership became more affordable, the demand for apartments decreased and the building community responded with fewer permit requests after 2002.

Data Source and Limitations

Data obtained from the 2002 King County Buildable Lands Report, King County jurisdictions and the Suburban Cities Association.

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Additional Resources

  • Trend in Achieved Density of Residential Development, King County Benchmarks, Land Use, 2008
    This indicator discusses achieved density. Monitoring changes in residential densities provides an opportunity to measure how efficiently our urban land is being utilized. Comparing achieved to planned densities is very useful at the jurisdictional level. However, planned densities vary greatly from zone to zone, and from city to city. At the sub-regional and County level it is more useful to compare average densities achieved currently to those achieved in the recent past.within each subarea throughout the county. From 2001 to 2005, nearly 26,000 units of new single-family development were permitted or finaled in the Urban Growth Area (UGA), an increase of 33% in permit activity.UGA-wide, over 25,000 multifamily units were permitted with an overall density of 38.0 DUs per net acre in the recent 5-year review period.