a. (1) Except as otherwise provided in section 25-312 of this chapter, it shall be unlawful for any person in charge of an improvement located on a landmark site or in an historic district or containing an interior landmark to perform any minor work thereon, or to cause or permit such work to be performed, and for any other person to perform any such work thereon or cause same to be performed, unless the commission has issued a permit, pursuant to this section, authorizing such work. (2) It shall be unlawful for any person in charge of any such improvement to maintain same or cause or permit same to be maintained in the condition created by any work done in violation of the provisions of paragraph one of this subdivision a.
b. The owner of an improvement desiring to obtain such a permit, or any person authorized by the owner to perform such work, may file with the commission an application for such permit, which shall include such description of the proposed work, as the commission may prescribe. The applicant shall submit such other information with respect to the proposed work as the commission may from time to time require. The commission shall promptly transmit such application to the department of buildings, which shall, as promptly as is practicable, certify to the commission whether a permit for such proposed work, issued by such department, is required by law. If such department certifies that such a permit is required, the commission shall deny such application, and shall promptly give notice of such determination to the applicant. If such department certifies that no such permit is required, the commission shall determine such application as hereinafter provided.
c. (1) The commission shall determine:
(a) Whether the proposed work would change, destroy or affect any exterior architectural feature of an improvement located on a landmark site or in an historic district or interior architectural feature of an improvement containing an interior landmark; and
(b) If such work would have such effect, whether judged by the standards set forth in subdivisions b, c, d and e of section 25-307 of this chapter with respect to an improvement of similar classification hereunder, such work would be appropriate for and consistent with the effectuation of the purposes of this chapter.
(2) If the commission determines the question set forth in subparagraph (a) of paragraph one of this subdivision c in the negative, or determines the question set forth in subparagraph (b) of such paragraph in the affirmative, it shall grant such permit, and it shall deny such permit if it determines such question set forth in subparagraph (a) in the affirmative and determines such question set forth in subparagraph (b) in the negative.
d. The procedure of the commission in making its determination with respect to any such application shall be as prescribed in subparagraph two of subdivision a of section 25-306 of this chapter, except that any period of thirty days referred to in such subparagraph shall, for the purposes of this subdivision d, be deemed to be twenty days.
e. The provisions of this section shall be inapplicable to any improvement mentioned in subdivision a of section 25-318 of this chapter and to any city-aided project.