Rooftop projects such as the St. Francis Hospital, Family Respite Garden require structural, yet lightweight materials to deliver unique architectural (or naturalistic) finishes but at lighter weights than typical masonry construction. Specifically, the St. Francis design team desired the look of architectural stone retaining and seat walls within the garden space. By using a polystyrene core and a glass-fiber reinforced concrete (GFRC) application, COST was able to deliver the look of an architectural stone wall but at 50% of the weight. The durability of the GFRC provided the structural reinforcement needed to retain planters, while the flexibility of finishes available allow for nearly any style, texture and coloration. Furthermore, the prefabricated nature of the wall fabrications, allowed for a much shorter jobsite duration as pieces were easily set in place by crane (see photo), anchored and immediately backfilled.