Density Bonuses

Density bonuses are granted for projects in which the developer agrees to include a certain number of affordable housing units. Essentially, for every one unit of affordable housing a developer agrees to build, a jurisdiction allows the construction of a greater number of market rate units than would be allowed otherwise. Most often, density bonuses vary from project to project and do not exceed a particular threshold (for instance, 20% of normal density) determined by local officials.


  • Permits developers to build more units at a site than regular zoning allows.
  • Provided in exchange for the developer’s agreement to build affordable housing on site.
  • Density thresholds (such as 20% of total density) are set by local jurisdictions.
  • Bonuses can be provided at no cost to local governments.

In Practice

San Diego, California. The County of San Diego has four specific density bonus policies.

The State Density Bonus Law allows a 25% increase in the number of housing units with the requirement that for the next 30 years, at least 10% of total units be reserved for very low-income households, or 20% of total units be reserved for low-income households, or 50% of total units be reserved for qualifying senior citizens.

The Affordable Housing for the Elderly Program targets senior citizens requiring that all units house elderly households with 35% of total units reserved for very low-income elderly households. Although the increase in the number of allowable units is negotiated on a case-by-case basis, this policy allows up to 45 units per acre within designated areas. 

The Mobile-home Park Density Bonus permits mobile home park developments a density of up to 8 units per acre within and beyond established urban service areas. 

The Housing for Lower Income Families Program allows the development of low-income housing with up to 20 units per acre in designated areas, provided that all of the units are affordable to low-income families.

Arlington County, Virginia. In the early 1980s, Arlington officials were using 15 percent density bonuses in select areas of the county. By 2001, the county began granting 25 percent bonuses to promote mixed-income housing developments containing units affordable to low and moderate-income families. The market rate units are designed to offset the costs of the affordable units contained within the property. Today Arlington County uses density bonuses in a variety of land-use and planning incentives to promote the production of new affordable housing units throughout the county.

Ashland, Oregon. In the city of Ashland, there is a current Land Use Ordinance in effect. This ordinance has a provision which allows for a 15 percent density bonus if conservation measures are installed in homes. There is a simple table that is used which lists these conservation measures and the points associated with these measures. Fifteen points must be earned from the table from each home in the area that a density bonus was granted. Because of changes in building practices and property sizes, it has been easy for the builders to comply with the 15 points.

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