Project Type: Construction Administration & Design
The Vital Structure:
Bio-Science Bldg. Reroof, Waterproofing and Enclosure
Issue
The building located in Cambridge, MA is a fourteen-story office building constructed in the early 2000s and is a LEED Platinum Structure. The steel-framed building includes systems such as glass curtain walls, insulated metal panel cladding, low-slope main roof, with an inverted roof membrane system (IRMA). Lower balcony roof systems extend around the perimeter at varied elevations. Large cooling towers, and structural steel dunnage support systems, along with fall arrest/window wash davit systems supported upon reinforced concrete piers are located around the perimeter of the upper roof. The tenant has moved out, and in combination with a building fit-out, the roof system replacement and associated work were coordinated to resolve a long history of a roof leak and related deterioration.
Diagnosis
The IRMA roof system was installed upon a flat (un-sloped) structural roof deck. It was apparent that the flashing details between the roof system and wall panels was insufficiently terminated and transitioned, resulting in roof and wall leaks, with water infiltration into the building occupied space, and corrosion of metal flashing, wall panels and metal framing. Steel dunnage support framing was found to be corroded. Roof davit support bases were temporarily removed for the reroofing, and found to have insufficiently torqued anchor bolts, and de-bonded anchors requiring augmentation.
Solution
Although Vital Structures was only contracted for Construction Administration services, we were engaged for design support to resolve many structural deck repairs, roof deck slope and drainage improvements, upgrading energy efficiency and flashing transition/termination conditions with elevation modifications, and application of screed mortars at balcony roofs to achieve positive roof slope to drains. Roof fall arrest davits required a structural design to retrofit galvanized steel plate sleeves with adhesive anchor shear lugs in order to fit over concrete piers and reestablish the needed davit anchor bolts to meet current OSHA and ANSI test standards.
Result
Vital provided review of the original engineer’s design documents and prepared documentation with improved approaches and materials to resolve unforeseen and problematic conditions. The client experienced a dramatically improved positive roof drainage system with appropriately transitioned flashing to eliminate leaks. Corroded steel dunnage was recoated to extend the serviceable life of the mechanical unit supports in lieu of framing replacement, saving them considerable funds. Life/safety improvements were achieved with the resolve of Vitals davit base sleeve custom design, so that the existing davit cranes could be salvaged and reused.
