Image courtesy of Thermory USA

Shown is a thermally modified white ash decking board.

Design and Construction Flexibility with Wood

CASE STUDY: 345 HARRISON, BOSTON

Photos: © Bill Horsman; courtesy of Bison Innovative Products

The 345 Harrison apartment building in Boston features a rooftop lounge area with a 12-person fire pit (left) and dog park with synthetic turf (right).

Copley Wolff Design Group and CBT Architects designed a versatile rooftop space using a pedestal deck system with modular wood tiles for the 345 Harrison apartments located in the desirable South End neighborhood of Boston. Apartment living has become more competitive in the nation’s top markets, and Boston is no exception. This neighborhood is home to vintage shops, jewelry stores, antique furniture markets, and urban eateries all within walking distance of this apartment building. The apartment’s amenities include a rooftop dog park accomplished with synthetic turf, a pool with surrounding pool deck finished with stone paver tiles, and a lounge area with gas grills, seating, and a 12-person fire pit with glass details. All these amenities express the building’s upscale character and are supported by an underlying pedestal system structure.

Smooth 2 x 2 ipê wood tiles were placed over an adjustable pedestal system to provide modularity. The pedestal system supports more than just the 2 x 2 ipê wood tiles—it also supports traditional joist and plank ipê decking, concrete pavers, and artificial turf for the dog park, thus expanding the variety of surface materials found on this rooftop space. This case study is an example of an outdoor space that benefits both people and the environment. It provides a rooftop garden that encourages social interaction, outdoor activity, and relaxation while reducing heat transmission into the environment.

Thermally modified wood products provide extensive flexibility for both designers and contractors. Wood used as decking is durable, dimensionally stable, and retains a smooth finish. The wood can be pre-oiled or unoiled. It comes in widths of 3.5–7.5 inches and has a thickness of 0.79–1.65 inches. Thermally modified wood boards can be installed using clips, screws, or PaCS. PaCS are strips on the underside of each wood board that allow the installer to just click the board into place. The installer simply presses down on the custom developed clip strip, and the board clicks into place. The wood boards are pre-grooved with tracks for the clips so alignment is automatic. There is no need for drill bits or screws, thus creating a clean look with no hazards to bare feet.

Photo: Ryoma Tominaga

Michael Van Valkenburgh Associates used ash to design an outdoor deck at The Gathering Place located along the Arkansas River 2 miles from downtown Tulsa, Oklahoma.

As an example, ash decking was used by Michael Van Valkenburgh Associates in the design of an outdoor deck for a project along the Arkansas River 2 miles from downtown Tulsa, Oklahoma. The hot summers and riverfront location inspired many of the design elements, including pedestrian land bridges and the outdoor dining deck.

Photo courtesy of Bison Innovative Products

A pedestal system supports modular wood tiles.

Design Flexibility with Versatile Modular Pedestal Systems

Pedestal systems can be utilized over any structural surface: on structural concrete, rigid insulation, or roof membranes for rooftop decks, plazas/terraces, compacted grade, pavements, pool surrounds, or within water features. These pedestal systems are comprised of two major components: pedestals and tiles/pavers. The pedestals are designed to elevate and support a variety of surfaces, including structural porcelain, stone, granite or concrete pavers, wood tiles, composite materials, fiberglass grating, or conventional joist and plank systems.

The pedestal system offers tremendous design flexibility coupled with ease of installation. An adjustable pedestal system provides a unique and viable alternative to traditional deck-building systems for the following key reasons:

1. They are available in a range of heights and weight-bearing capacities to suit a variety of applications.
2. They are one of the most labor- and cost-efficient methods of creating a flat, level structure over a sloped surface.
3. They use a gravity system that protects roofing and waterproofing materials without damaging or harming the surface below.
4. They can support decks over occupied spaces, allowing room for electrical systems, duct work, or irrigation to pass underneath the surface material.

The pedestals can be made from high-density polypropylene plastic (comprised of 20 percent post-industrial recycled content) that is 100 percent recyclable. The recycled material content of the pedestals provides points toward both LEED and SITES certification. The pedestals are screw adjustable and easily leveled with tapered base leveling discs and/or shims, allowing the creation of level rooftop surfaces over a variety of conditions, including sloped surfaces. The pedestals can elevate and support wood tiles, concrete pavers, and a variety of other surfaces when sophisticated, commercial-grade decking is required. They are also sturdy enough to support site furnishings such as planters, tables, benches, and/or structures such as pergolas.

Design Options using Pedestal Deck Systems

The pedestals come in residential, commercial, and industrial grades, with each grade having different characteristics. Deciding which systems to specify is dependent on the support and elevation requirements of the installation. These pedestal systems provide designers with options for creating valuable outdoor spaces for owners and their clients, customers, and visitors. Rooftop decks are a way for residential, hospitality, or public spaces to differentiate themselves from the competition.

A pedestal system is also an ideal method to incorporate a water feature application onto a rooftop garden. The system conceals the water supply beneath the pedestals and surface materials and allows water to drain to the surface below for recycling. Additionally, the pedestal supports are impervious to water, mold, and most chemicals.

These pedestal systems also provide designers with the opportunity to include recessed lighting below the surface. Lighting can be selectively located to enhance the ambiance of the environment and improve visibility and safety during nighttime and/or dark conditions.

Ground-level and street-level sidewalks and storefronts can be expanded through the design of mini-decks, parklets, or pop-up parks, all of which enhance urban communities. These mini-decks, parklets, and pop-up parks can be designed using pedestal systems and modular wood tiles placed over existing ground and street-level spaces. These exterior spaces provide areas that support social connections, mental restoration, and physical activities that meet criteria under Site Design: Human Health and Well-Being in the SITES guidelines.

Fastening kits and splines facilitate quick and secure pedestal deck system installations. The fasteners attach kerf-cut wood tiles, concrete, and stone pavers or paver tray-backed porcelain tiles to the pedestals without penetrating or damaging the selected surface material. While the fasteners are hidden, they can be accessed to allow for the removal of individual wood tiles or pavers if roof maintenance, drain access, or tile replacement is required. Some pedestal systems can also be designed to resist wind uplift. It is important to consult with individual manufacturers and engineers for confirmation on the capabilities of their systems.