D.C. Mun. Regs. tit. 20, r. 20-2802
From 7:00 a.m. to 7:00 p.m. on any weekday, noise levels resulting from construction or demolition (excluding pile driver devices) shall not exceed a Leg(1.) of eighty (80) dB(A) unless granted a variance under § 2705 of Chapter 27 of this subtitle.
From 7:00 p.m. to 7:00 a.m. the maximum noise levels prescribed in § 2701 of Chapter 27 of this title shall apply.
In cases involving noise from construction or demolition, measurements shall be made twenty-five feet (25 ft.) from the outermost limits of the construction site; provided, that when construction work is performed inside an occupied multi-unit apartment building, hospital, nursing home, community-based residential facility, or other similar facility which serves as a temporary or permanent dweling for its residents, measurement of noise from the construction or demolition shall be made twenty-five (25) feet from the source of the noise. This provision shall be subject to the exemption for emergency work.
No permit for building construction or demolition shall be issued until the permit applicant has assured in writing that the noise emanating from the planned construction will comply with the limitations established by this section.
D.C. Mun. Regs. tit. 20, r. 20-2802