Shared Outdoor Spaces

With these large openings available for even mid-rise and high-rise apartments, the indoor-outdoor craze that swept the custom home industry over the last decade has had a pronounced effect on multifamily environments. Many of the outdoor settings are private, but the increased expectations for shared amenities and common spaces—especially for so-called lifestyle residences where community and socializing are part of the sell—have led to more programming of communal zones. Rooftop clubrooms, open terraces, and pools as well as shared balconies and courtyards are now common features highlighted by realtors.

Gravity-based, modular pedestal deck systems are used on flat rooftop terraces as pool surrounds, green roofs, water features, and even lawn bowling courts. Photo courtesy of Bison Innovative Products

Whether for new buildings or renovations, the key challenges include activating roof areas and beautifying the surroundings while also protecting the roof membrane and drainage elements, such as soft metal flashings. Pedestal decking, which are gravity-based modular systems, have in recent years been applied to flat rooftop terraces as pool surrounds, green roofs, water features, and even as upper-floor dog parks and bocce lawn bowling courts. The systems use deck point supports topped by varied flat surfaces such as wood and stone tiles and concrete pavers.

“The pedestal systems do not penetrate or attach through waterproofing or roofing membranes, and they also eliminate the need to connect to parapet walls or use joists,” says Bison Innovative Products' von Gunten. Building systems are accommodated below the pedestals, such as roof drains, piping, irrigation for roof gardens, and even low-voltage lighting. The modular elements are fitted to a 2-foot grid, and they are lightweight and relatively small enough to ease transport to upper floors, she adds. Typical materials include Ipé and other weather-resistant deck tiles. Used with water features, the pedestals sit within pools and fountains.

Keeping these outdoor, shared spaces safe is critical to project owners, and some pedestal systems have been developed to meet seismic criteria and ASTM standards for fire resistance. One of the challenges for high-rise developments and locations with potential for severe weather has been wind uplift, says von Gunten, and the air-permeable pedestal decks help equalize uplift forces, restraining the decks and tiles from movement. Although there is no specific standard for testing the decks, engineers have applied the Florida Building Code's Testing Application Standard (TAS) 108, Test Procedure for Wind Tunnel Testing of Air Permeable, Rigid, Discontinuous Roof Systems.

The rooftop systems also have a positive effect on enclosure performance, both protecting the underlying roof membrane and helping to reduce solar heat gain on large, flat roof expanses. This performance benefit dovetails neatly with the overall trajectory of today's designs for multifamily building enclosures, where better thermal control, air barriers, and moisture management are driving new construction techniques.