While Twitter is grabbing headlines for the pending departure of CEO Dick Costolo, and Shorenstein is quietly shopping the two Mid-Market buildings in which Twitter is headquartered, we gaze upward at the first renderings for the proposed sky-bridge which would physically connect the Market Square buildings and Twitter’s staff.
As designed, the 38-foot sky-bridge over Stevenson Street would connect the 9th floors of 1355 Market and 875 Stevenson, with an overlook from the 1oth Floor of 875 Stevenson across the bridge.
From San Francisco’s Planning Department which is preparing the proposed sky-bridge for its required Historic Preservation review:
“The new sky-bridge, as currently proposed, appears to be consistent with the [Historic Preservation] Standards in that it is located on a secondary façade, ensuring it will not alter any character-defining features of the building. The removal of the two non-original windows on the 9th floor will not substantially alter the fenestration pattern on this façade. The design of the sky-bridge is expressed as a three-dimensional object in that it tapers-in vertically while it tapers-out horizontally towards the building at 1355 Market Street.
Additionally, the shingled glass design on both sides of the sky-bridge and shingled aluminum surface of the underside of the sky-bridge adds to its three-dimensional expression, providing visual interest to patrons of the new public plaza below. Furthermore, the proposed lighting on the underside of the bridge will relate the sky-bridge to the existing lighting pattern in the public plaza below. The overall size of the connection points of the sky-bridge will ensure the rhythm of the window openings on the upper floors of the rear façade at 1355 Market Street is continued by aligning the outer edges of the sky-bridge with the sides of the paired existing windows. As such, the proposed sky-bridge will not destroy historic materials and will not detract from the historic character of the subject building.
The sky-bridge is designed to read as a contemporary addition that is sufficiently differentiated from the historic features of the existing building at 1355 Market Street. Additionally, the location of the sky-bridge on the rear façade of the 1355 Market Street building and substantial setback from adjacent public right-of-ways ensures the sky-bridge reads as a secondary and subordinate addition to the historic resource. Furthermore, the overall design of the sky-bride relates to previous alterations made to the 1355 Market Street building and approved by the [Historic Preservation Commission].”
That being said, in order “to ensure the design of the sky-bridge is expressed as three-dimensional and dynamic,” Planning staff is recommending that “the glass shingles be comprised of single panels for the full height of the sky-bridge” and each panel “be comprised of insular, single pane (low iron) glass units without frames rather than the proposed 1-inch insulated glass units with kynar finish aluminum frames.”