New Zoning Rules Impacting DC Home Additions

How Do DC’s New §§ 306.3 and 306.4 Impact Rear Additions?

2017 changes to DC zoning laws will restrict the size of rear additions to Washington DC homes. Under new guidelines taking effect in April, the following provisions restrict the size of rear additions for some home types:
  • The proposed text amendments address concerns about excessively disproportionate rear extensions adjoining attached and semi-detached buildings in the R-2, R-3, R-13, R-17, R-20, and RF zones by adding language limiting a matter-of-right rear extension to such buildings, whether as an addition to an existing building or as new construction, from extending further than ten feet (10 ft.) beyond the farthest rear wall of an adjoining principal residential building on an adjoining property.

What Types of Properties Are Affected?

  • The proposed limitation does not apply to detached buildings because a detached building, including any rear addition, would be subject to side yard requirements that provide separation from adjacent buildings.

Are Special Exceptions Allowed?

The amendments allow a rear extension to extend further than ten feet (10 ft.) if approved as a special exception.

Do The Rules Vary by Neighborhood?

Here’s a copy of the proposed Amendment for review of changes by neighborhood:
Exhibit10-3 Rear Addition Zoning Amendment

What is the General Purpose of the Amendments?

The recommended text amendments address concerns about excessively disproportionate rear additions to adjoining row buildings. The text reflects the 10 ft. standard approved by the Zoning Commission on March 28, 2016 as a minor modification to the special exception criteria for conversion of a rowhouse to more than two units in case 14-11. In this case, the rear addition language establishes a ten foot limit as a matter of right and would allow for more than ten feet as a special exception. The new language would be applicable in combination with the other existing development standards such as lot occupancy and rear yards, to regulate the overall development of a lot. The ten foot rear addition limit could not be used to encroach into a required rear yard or to exceed lot occupancy.


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