Rooftop athletic field built at WPI with MIRAFI

Overview

In recent years, student enrollment at Worcester Polytechnic Institute (WPI) has increased, and thanks to the success of the WPI varsity athletic program, participation in athletics has grown by over 60%. To address the shortage of both parking spaces and athletic fields, WPI decided to build the first ‘Rooftop Field’ in Massachusetts atop a new parking garage.

Although parking garages are no longer eligible for LEED certification, this new combination facility is designed as a sustainable building. It includes features such as stormwater management, energy efficiency, an electric charging station, and the use of recycled materials. Most importantly, the project makes a sustainable statement by using the land for two purposes under one footprint.

When completed, the facility will provide ample parking along with a rooftop athletic field. The field will accommodate softball, soccer, field hockey, lacrosse, rugby, and a variety of other recreational activities.

Challenge

The challenge for WPI was to build several new athletic fields while also increasing parking capacity to accommodate the growing student population and the rise in large-scale campus events. These include sporting events, robotics competitions, admission open houses, career fairs, and alumni gatherings, all without sacrificing usable campus space.

Additionally, WPI’s Board of Trustees mandated that the project be as sustainable and environmentally compliant as possible.

Solution

Once the 534-space parking structure was completed, construction of the synthetic rooftop athletic field began. First, a PVC geomembrane [BK1] [KG2] was placed over the concrete roof deck to provide waterproofing and direct stormwater to designated drainage outlets.

Next, MIRAFI^® S800, a nonwoven geotextile, was laid directly over the membrane to offer cushioning and protection. A lightweight plastic air drainboard, approximately 2 inches (5 cm) thick, was then installed on top of the MIRAFI S800. This drainboard provided a thinner, more lightweight alternative to traditional drainage stone while keeping the synthetic turf well-drained and dry.

The drainboard was then covered with another layer of MIRAFI S800 to enhance drainage. On top of this, MIRAFI RS380i was installed, followed by a 6-inch (6 cm) layer of stone ranging from 6 to 12 inches (6 cm – 30 cm) in size. The synthetic turf field was then placed over this foundation.

The MIRAFI RS380i geotextile provided excellent separation and drainage to manage stormwater infiltration. It also acted as a reinforcement layer, significantly reducing the required thickness of the aggregate to support the turf. This reduction in aggregate also lessened the overall weight load on the roof deck, delivering considerable cost savings to WPI.