Glossary
Density Bonus
A density bonus is extra buildable density a local government grants a developer in exchange for setting aside affordable units or providing a public benefit. It lifts the number of units, floor area, or height allowed above baseline zoning, and the size of the bonus scales with the depth and share of affordability provided.
How a Density Bonus Works
A density bonus is calculated as a percentage increase over baseline density, tied to the share of units set aside as affordable. Under California's Density Bonus Law, Government Code Section 65915, a project reserving 5 percent of units for very-low-income households earns a 20 percent bonus, rising to a 50 percent bonus at a 15 percent set-aside.
The schedule differs by income tier. The California Department of Housing and Community Development sets a 20 percent bonus for a 10 percent low-income set-aside, reaching 50 percent at a 24 percent set-aside, and a 5 percent bonus for a 10 percent moderate-income (for-sale) set-aside, reaching 50 percent at a 44 percent set-aside.
Depth of affordability also unlocks concessions and waivers. A concession, or incentive, modifies a development standard to reduce affordable-housing cost, such as reduced setbacks, added height, or lower parking. Per the Southern California Association of Governments, a 5 percent very-low-income set-aside earns one concession and a 15 percent set-aside earns three. Waivers, which remove standards that would physically preclude the awarded density, are unlimited so long as the applicant shows they are needed to build the project.
Why a Density Bonus Matters
A density bonus is the mechanism that makes affordability pencil for a developer, because the added market-rate units recover revenue lost to deed-restricted rents. The density bonus is the most common incentive used by inclusionary housing programs, per Local Housing Solutions, which lets a project recoup below-market income by selling or leasing more units at market rates.
The bonus also shifts the negotiation. In a jurisdiction with a mandatory state schedule, the additional density is an entitlement the developer can claim, not a discretionary favor a planning board may withhold. That certainty changes how a site underwrites: buildable capacity, and therefore land value, rises the moment a qualifying affordable set-aside is on the table.
Poorly designed offsets create the opposite effect. If the bonus does not cover the revenue foregone on below-market units, an inclusionary requirement becomes a tax on new supply, discouraging development and pushing prices up rather than down. The density bonus exists to keep affordability from choking off the market-rate housing that funds it.
Example
A density bonus is easiest to size on a fixed baseline. Take a site zoned for 100 units. The table below applies California's statutory schedule across income tiers, showing the set-aside percentage, the resulting density bonus, the total units permitted, and the bonus units gained on that 100-unit base.
Income tier | Affordable set-aside | Density bonus | Total units | Bonus units |
|---|---|---|---|---|
Very low (50% AMI) | 5% | 20% | 120 | 20 |
Very low (50% AMI) | 15% | 50% | 150 | 50 |
Low (80% AMI) | 10% | 20% | 120 | 20 |
Low (80% AMI) | 24% | 50% | 150 | 50 |
Moderate for-sale (120% AMI) | 10% | 5% | 105 | 5 |
Moderate for-sale (120% AMI) | 44% | 50% | 150 | 50 |
Take the very-low-income row at a 15 percent set-aside. The project deed-restricts 15 units and earns a 50 percent bonus, 50 additional units, for 150 total. Fifteen units carry affordability restrictions, leaving 135 market-rate units against the 100 a baseline project would have sold. At a representative $80,000 in developer value per net market-rate unit, the 35 additional market-rate units add roughly $2,800,000. The $80,000 figure is a representative input, not a quoted comparable.
Variations and Edge Cases
A density bonus is defined by whichever government sets it, so terms vary widely. California's Density Bonus Law is a statewide floor that local agencies must honor, while many cities run their own inclusionary programs with different set-aside thresholds, bonus percentages, and eligible income tiers. Federal housing policy encourages the tool but does not standardize it.
Variation | Description |
|---|---|
Statewide statute | California Government Code 65915 sets a mandatory schedule local agencies must grant |
Local inclusionary programs | Cities set their own set-aside and bonus figures, often layered on the state floor |
Stacked bonus (AB 1287) | Effective January 1, 2024, a project maxing the base bonus can seek an additional bonus up to 50 percent, per Hanson Bridgett |
Concessions and waivers | Set-aside depth unlocks one to three concessions; waivers of standards that physically preclude the project are unlimited |
The stacked bonus is the sharp edge. Under AB 1287, a California project that already maximizes the base bonus, 15 percent very-low-income, 24 percent low-income, or 44 percent moderate-income, can request an additional density bonus of up to 50 percent, pushing the combined increase toward a doubling of baseline density. A concession can be denied only where the local agency finds it produces no cost savings for the affordable units.
Density Bonus vs Floor Area Ratio
A density bonus is often confused with floor area ratio. A density bonus is a percentage increase in allowed development granted in exchange for affordable units. Floor area ratio, or FAR, is the fixed ratio of buildable floor area to lot area that sets the baseline a density bonus increases.
The distinction is baseline versus bonus. FAR is a standing rule that caps what any project may build. A density bonus is a conditional lift above that cap, earned only by providing affordability. The bonus can be delivered as extra units, added floor area, or additional height, so the two interact directly: a density bonus often raises the effective FAR a site can achieve.
Frequently Asked Questions
How big can a density bonus get? Under California's Density Bonus Law, the base bonus tops out at 50 percent for a project reserving 15 percent of units for very-low-income households. Since AB 1287 took effect January 1, 2024, a project that maxes the base bonus can stack an additional bonus of up to 50 percent.
What is the difference between a concession and a waiver? A concession, or incentive, reduces a development standard to cut affordable-housing costs, such as lower parking or greater height, and a project unlocks one to three based on its set-aside. A waiver removes a standard that would physically prevent the project from building its awarded density, and the number of waivers is unlimited.
Does a developer have to provide affordable units to get a density bonus? Yes. A density bonus is conditional. The additional density is granted only in exchange for deed-restricting the required share of units as affordable, or in some programs for another qualifying public benefit such as senior housing or land donation. Removing the affordable commitment removes the bonus.