D.C. Mun. Regs. tit. 11, r. 11-631
In the CR District, the floor area ratio of all buildings and structures on a lot shall not exceed six (6.0), not more than three (3.0) of which may be used for other than residential purposes.
For the purposes of this section, the term "residential purposes" shall include dwellings, flats, multiple dwellings, rooming and boarding houses, community-based residential facilities, inns, and guest room areas and service areas within hotels, except that this term shall not include guest room areas and service areas within hotels located or proposed to be located on CR zoned property in the Capital Gateway Overlay District as established by Chapter 16 of this Title or the Southeast Federal Center Overlay District established by chapter 18 of this Title.
For the purposes of this section, the allowable residential and nonresidential bulk of a CR District may be apportioned between two (2) or more lots in the same square, regardless of the limits on floor area; provided, that the aggregate residential and nonresidential floor area may not exceed the limits for the CR District.
A covenant running with the land and applicable to all properties involved in the apportionment shall be executed by all of the owners of the properties and the District of Columbia government prior to the issuance of any building permits. The covenant shall be for the purpose of insuring that the aggregate residential and nonresidential floor area does not exceed the limits applicable to residential and nonresidential uses.
D.C. Mun. Regs. tit. 11, r. 11-631