Washington, DC Zoning Overlays & Bonuses: Density Bonus Law (2026)

Under 11 DCMR Subtitle C § 1002, a development that qualifies as an Inclusionary Development under the IZ program administered through the Zoning Regulations of 2016 can use a bonus density incentive: it "may construct up to twenty percent (20%) more gross floor area than permitted as a matter of right ('bonus density')" in exchange for meeting the affordable-unit set-aside requirements of Subtitle C § 1003. The 20% bonus is available in most zones but is expressly denied in the BF, HE, NHR, R, RF, SEFC, StE, and WR zones, where separate development standards govern.

The bonus is not automatic: it applies "as reflect in the zone-specific development standards and subject to all other zoning requirements (as may be modified by the zone) and the limitations established by the Height Act," meaning the citywide Height Act ceiling still controls even where the 20% IZ bonus would otherwise allow more floor area. A project that has already used its full IZ bonus density can still seek additional bonus density available under other chapters of Title 11, provided its combined density does not exceed the FAR maximum tied to the zone that grants that additional bonus.

Applicability turns on the definitions in Subtitle C § 1001: a "Mandatory Inclusionary Development" is triggered by proposals to create ten or more new dwelling units (including cellar or penthouse units) by adding new gross floor area, converting existing floor area to residential use, or a combination of both, while smaller projects may opt in voluntarily as a "Voluntary Inclusionary Development" if the owner agrees to set aside at least one Inclusionary Unit. The set-aside percentage that unlocks the density bonus is spelled out in Subtitle C § 1003: buildings with a by-right height of 85 feet or less that do not use Type I (fire-resistant) construction must set aside the greater of 10% of residential gross floor area or 75% of the bonus density utilized, while taller or Type I buildings set aside the greater of 8% of residential gross floor area or 50% of the bonus density utilized.