For developments or enlargements of Quality Housing buildings in which at least 50 percent of the dwelling units are income-restricted housing units, or at least 50 percent of its total floor area is a long-term care facility or philanthropic or non-profit institution with sleeping accommodation, the Board of Standards and Appeals may modify the underlying bulk regulations, other than floor area ratio, provided that in no event shall such building height or the number of stories therein exceed those set forth in paragraph (b) of Section 23-664 (Modified height and setback regulations for certain Inclusionary Housing buildings or affordable independent residences for seniors), and provided that the Board finds that:

(a)        there are physical conditions, including irregularity, narrowness or shallowness of lot size or shape, or topographical features that create practical difficulties in complying with the bulk regulations for Quality Housing buildings and would adversely affect the building configuration or site plan;

(b)        the practical difficulties of developing on the zoning lot have not been created by the owner or by a predecessor in title;

(c)        the proposed modifications will not unduly obstruct access of light and air to adjoining properties or streets;

(d)        the proposed scale and placement of the development or enlargement relates harmoniously with the surrounding area; and

(e)        the requested modification is the least amount necessary to relieve such practical difficulties.

The Board may prescribe appropriate conditions and safeguards to minimize adverse effects on the character of the surrounding area.