A developer with a penthouse apartment in a building in Uptown Manhattan asked us to investigate the possibility of adding a second story to his unit. The plan would offer the condominium association a second adjacent rooftop unit for common use in exchange for the developer’s rights to construct his private penthouse addition on the east side of the roof.

At thirty-two stories, the roof is near the upper limits for feasible access by very large mobile crane. Permitting for crane access is relatively complex and increasingly so with lengthier street-closure times. Hourly crane time is very expensive as well, and insurance and safety risks rise dramatically as the length of crane time, numbers of individual truck deliveries, and number of lifts increases. For all of these reasons, a substantially complete prefabricated building module is very sensible. A very large and heavy unit creates other problems, however, so there are still offsetting considerations for less prefabrication with smaller sub-assemblies. For this project, we settled on the complete module system, but we have simultaneously developed a system of elevator-sized, folding structural components that could be brought up to the roof in many compact parcels and then quickly deployed on the roof top.