Rooftop Penthouses

First – what is a rooftop penthouse? In DC, it is a (usually) small rooftop structure sitting on top of the roof, containing things like mechanical equipment, elevator or stairwell over-runs, and sometimes a room supporting a rooftop deck – storage, washrooms, etc. Not every building has one, in fact, most one-family homes and rowhouses and many small commercial or apartment buildings do not. Where they do exist, you may not always notice them, since they are required to be set back from the edge of the building below, to minimize their visual impact.

Mechanical Penthouse 2

Penthouses are regulated by zoning, including their size, height, setbacks, and permitted uses. Generally, the current penthouse regulations:

  • Limit penthouses to a height of 18’-6” above the building roof;
  • Do not limit the number of stories within the penthouse;
  • Require the penthouse to be set back from the edge of the building roof below by a distance equal to the penthouse height (a 1:1 set back); and
  • Do not permit “habitable” space in the penthouse. Habitable space includes uses such as residential living space, office space, conference rooms, or rooftop commercial space like a rooftop bar or lounge.

penthouse - aerial

The federal Height Act of 1910 also regulates penthouses. It was amended in 2014 to allow any use, including habitable space, within a rooftop penthouse which is one story and 20 feet in height or less. The intent was to allow greater use flexibility for roof tops and penthouse space. The DC zoning regulations are more restrictive than the federal Height Act, and any new building or addition must conform to both the zoning and the Height Act. To bring the Height Act and the more restrictive zoning regulations more in line and to implement the intent of the Height Act changes, amendments to the penthouse regulations would be needed.

The Zoning Commission held a public hearing on November 6, 2014 on the original OP proposed amendments to the penthouse regulations. In response to the public comments received, the Commission instructed OP to prepare an amended set of penthouse zoning regulation alternatives, to be re-advertised for a new public hearing. The new alternatives include the following:

  • Permitted penthouse height: Allow a penthouse of 20 feet in height above the roof it sits on (an increase from the currently allowed 18’-6”) in some higher density zones, but limit height to 10 feet (a decrease from the currently allowed 18’-6”) in any zone in which the building height is limited to 50 feet or less by right. The Commission is also considering an amendment to not allow a penthouse at all on a single family dwelling or rowhouse.
  • Permitted number of stories, not currently regulated by zoning: Allow 2 stories in zones that would allow a penthouse of 20 feet in height, but one story where the permitted penthouse height is limited to 10 feet. In the alternative, allow one story of habitable space in any zone, but allow a second story for mechanical space in zones where a 20 foot tall penthouse is permitted.

penthouse - 50' building

  • Permitted uses in a penthouse: Allow habitable space (residential units, office space, commercial space) in a penthouse in higher density zones, but not allow habitable space in zones where the building is limited to either 40 or 50 feet in height, or on top of a single family home or rowhouse. The Zoning Commission will also discuss whether certain uses such as a restaurant or nightclub (if permitted in the zone) would be permitted in the penthouse only with Board of Zoning Adjustment review of a special exemption request, to assess potential impacts on neighboring properties.
  • Penthouse setbacks: Essentially retain the current requirements, but provide clarification in the language when the setback is required, and also require a new penthouse setback from an adjacent historic property.
  • Penthouse area: Alter or generally eliminate current restrictions on the area of the roof that could be covered with penthouse structure – penthouse size would mainly be limited by required setbacks.
  • Penthouse walls: Amend and clarify design-related requirements for penthouse structures.
  • Affordable housing: Apply existing affordable housing requirements to new penthouse residential and non-residential space, and apply them more broadly and potentially at a deeper level of affordability.
  • Parking: Consider whether new penthouse habitable space triggers additional parking requirements.

For more detail and additional analysis, including a comparison of the proposals to existing zoning regulations, please refer to:

These changes will be discussed at a Zoning Commission Public Hearing to be held the evening of April 30, 2015 – you can participate by providing written comments to the DC Office of Zoning in advance of the hearing, or you can submit written comments in advance. More information on how to do this is available on the DC Office of Zoning website. Please also feel free to contact the Office of Planning if you have additional questions or comments.