21.6.O Flat Roof Features

1. Accessory rooftop features of a flat roof, such as green roofs, rooftop decks, rooftop pools, rooftop gardens, and stormwater detention systems are permitted below the parapet of any flat roof building or flat roof portion of a building, and are excluded from the calculation of height and gross floor area, provided that the following standards are met:

a. Documentation shall be submitted demonstrating that the roof can support the additional load of plants, soil, and retained water, and that an adequate soil depth will be provided for plants to survive.

All planting materials and soils shall be of good quality and meet the American Standard for Nursery Stock (ASNS), latest edition, or equivalent for minimum acceptable form, quality and size for species selected. Vegetation shall be maintained in good condition, present a healthy, neat and orderly appearance, and be kept free of weeds, refuse and debris for the life of the building. Irrigation systems, when provided, shall be maintained in good operating condition to promote the health of the plant material and the conservation of water.

b. The roof contains sufficient space for future installations, such as mechanical equipment, that will prevent adverse impacts.

c. Rooftop decks or patios shall be set back five (5) feet from all building edges.

d. Guardrails shall be set back at least five (5) feet from the building edge.

2. Within the CBD Districts and the RIV-3 Bywater and RIV-4 Riverfront Overlay Sub-Districts, in addition to the accessory flat roof features provided above, elevator machine rooms, bathroom facilities, stair bulkheads, and elevator lobbies are permitted on any flat roof building or flat roof portion of a building, and are excluded from the calculation of height, stories and gross floor area, provided that the following standards are met:

a. Elevator machine rooms shall not exceed the minimum size necessary to house and service the equipment as specified by the equipment manufacturer. Elevator lobbies shall be limited to thirty-six (36) square feet in area per elevator opening. Collectively, elevator machine rooms, stair bulkheads, elevator lobbies and bathroom facilities shall not exceed fifteen percent (15%) of the area of the flat roof on which they are located.

b. Elevator machine rooms and elevator lobbies shall be limited to a height of fourteen (14) feet as measured from the roof surface.

c. Elevator machine rooms and elevator lobbies shall be set back from any building edge fronting an adjacent street by a distance not less than their respective heights.

3. Any of the following, if located on a rooftop, shall be included in the calculation of building height and number of stories:

a. Enclosed habitable space

b. Awnings

c. Pergolas

d. Trellises

e. Shade structures.