Bookmen Stacks Park Plaza

A park-like intensive green roof on top of the underground car park of a multi-storey development in central Minneapolis. It was designed with Oslund and Associates, installed in 2005 and photographed through to October 2016, an eleven-year record of the same roof.

The development needed to use every open space it had, and the only one available was the car park roof. That set a hard structural limit: whatever went on top had to weigh no more than 60 to 80 pounds per square foot when saturated, which is when a green roof is heaviest. The search was for an intensive, park-like roof that combined plant diversity, water management and light weight.

EPIC built its patented Muellner Green Roof™ with the landscape architects Oslund and Associates. From the top down, the profile is turf or planting, Muellner foam and a sand and shale layer, fine gravel, the EPIC System™ for passive irrigation and drainage, the roof membrane and the concrete deck. Stormwater is held in a 10,000 gallon tank and safely reused. The roof system is recyclable and made from local materials and post-consumer waste.

The case study says that every unit facing the green roof sold out, while units facing elsewhere were 75% vacant. It credits the higher occupancy to how usable, practical and attractive the space is. It also says the roof adds usable space, helps with water management, makes the roof membrane last longer and reduces hard surfaces on the site.