Credit: Erik Stekelenburg

The last two decades have seen a growing interest in ultralight architecture realized by the introduction of durable lightweight materials and advanced fabrication methods. Most intriguing is architects’ pursuit of dematerialization as a driving concept, which—in the relative absence of substance and ornamentation—allows structures to appear as if they are defying the very physicality of the materials with which they are constructed.

Ultralight architecture is one thing, but how about infrastructure? Bridges and roadways would seem to require the use of substantial construction materials not only to prevent physical failure but also to reassure travelers of their safety. Yet the Dutch firm RO&AD suggests an alternative, as evidenced by its infrastructure projects whose designs seem to counter physical practicality.

A recently completed floating bridge by the studio connects the Dutch city of Bergen op Zoom to the island fortress Ravelijn op den Zoom. The gracefully curving bridge spans 262 feet across a historical moat, following the trajectory once taken by rowboats carrying supplies to the fortress. It is made of lightweight Accoya acetylated wood planks, which are treated for resistance to moisture and decay with reduced shrinkage and swelling. The gently-cambered slats rest upon inflated polyethylene pipes that keep the bridge afloat with no other structure employed. The result is a delicate ridge of material that appears to tenuously traverse the water’s surface, doubtlessly inspiring an unnerving sensation for first-time visitors.

Credit: Erik Stekelenburg

RO&AD used Accoya for an earlier moat-crossing project: a sunken bridge at Fort de Roovere, also in The Netherlands. In this case, the designers created a pedestrian-sized trench crossing the waterway. Lined with impregnable woodsheet pilings, the bridge follows the contours of the moat and adjacent embankments to provide a navigable path with minimal visual intrusion. Visitors using the bridge seem to disappear partially into the landscape with their torsos peeping out above its razor-thin profile.

Credit: RO&AD Architects

During this time of fascination with ultralight architecture, light-touch infrastructure seems an equally significant and even more surprising endeavor. RO&AD’s bridge designs demonstrate the value that their nearly-immaterial constructions contribute to historically and environmentally sensitive contexts. Compared to more conventional and substantial structures, RO&AD’s floating bridge and sub-aqueous crossing call positive attention to themselves—not for what is there, but for what is not.

Blaine Brownell, AIA, is a regularly featured columnist whose stories appear on this website each week. His views and conclusions are not necessarily those of ARCHITECT magazine nor of the American Institute of Architects.