Trends in Urban Outdoor Amenity Spaces  

Real estate studies show that urban housing demands are on the rise. Members of the baby boomer generation looking to retire seek smaller residences that are easier to maintain and desire being in urban areas where they can readily access public transit, quality medical care, and other lifestyle preferences. Members of the millennial generation want the convenience of living and working in urban areas that offers a wealth of amenities and a variety of transportation or walkable options.

As the demand for urban housing increases, developers are expected to provide more and better amenities that add value to housing properties and entice potential renters and urban home/condo buyers.

Photo courtesy of Daniel Weinbach & Partners Ltd.

This aerial view shows the eighth-floor amenity deck and gardens at Hubbard Place, Chicago.

Roof decks and terraces are now a must-have amenity space in urban environments and are easily added without increasing the building footprint by building out underutilized roof space. Roof decks provide outdoor spaces that are easily accessible to residents and can be designed to accommodate social and recreational needs. New outdoor roofs incorporate a wide variety of site amenities, including patios, dining and bar areas, putting greens, pools, garden spaces, and grilling areas.

Business owners are also looking for office spaces that offer amenities, as they help to increase usable office space, contribute to employee well-being by providing the opportunity for employees to get outside and walk or stretch, and reinforce the corporate brand identity of the integration of work and life, such as with large tech companies, all while creating a professional, creative, and collaborative environment conducive to better business. Commercial building owners now understand the importance of shared amenities as an attraction for high-quality office tenants, improving their tenant retention and increasing the overall building value.

There are a variety of products and materials that are utilized in the design and construction of roof gardens and decks. This course will review the basic types of roof systems as well as the range of hardscaping products that are available to designers.

The actual roof deck surface can be comprised of both hardscape materials and green planting areas. Roof deck areas can benefit the environment and human health and well-being by meeting certain Sustainable SITES and LEED criteria. In large part, they can help to reduce the effects from urban heat through the use of light-colored pavement surfaces and planting areas rather than the traditional roof surfaces of dark gravel and asphalt materials.

Some of the possible Sustainable SITES criteria that are applicable to roof deck systems include:

1. Site Context
   1. 1.6: Project located in an existing developed area
   2. 1.7: Project connects to multimodal transit networks
   
   
2. Site Design: Soils and Vegetation
   1. 4.9: Reduce urban heat island effect with lighter colors on roof
   
   
3. Site Design: Materials Selection
   1. 5.3: Design for adaptability and disassembly
   2. 5.5: Use recycled content materials
   3. 5.8: Support transparency and safer chemistry
   4. 5.9: Support sustainability in materials manufacturing
   5. 5.10: Support sustainability in plant production
   
   
4. Site Design: Human Health and Well-Being
   1. 6.4: Support mental restoration
   2. 6.5: Support physical activity
   3. 6.6: Support social connection

And the potential LEED criteria that are applicable to roof deck systems include:

1. Sustainable Sites
   1. 5.2: Maximize open space
   2. 7.2: Heat island effect
   
   
2. Energy and Optimization: Optimize energy performance through reduction of energy demand
   
   
3. Materials and Resources
   1. Recycled content
   2. Regional material

An Evolution of Roof Deck Systems

Over the past few decades, exterior building spaces and roofs have significantly transformed from utilitarian ballasted roof systems to roof systems with highly programmed, environmentally conscious, people-friendly amenities that promote healthier lifestyles. In the evolution of roofing systems, there are about five common types of systems currently used on commercial and large residential buildings. These include:

Conventional ballasted roof systems. These are the earliest types of flat roof systems, and they are still being used. They require flat roofs with slopes of no more than 2 inches height over 12 inches length (1:6). These systems consist of a membrane or a membrane and a substrate material that is loose laid over a deck using ballast to hold the system in place. The ballast is usually a crushed stone meeting ASTM D448 sizing. ASTM D448 stone ranges between 1.5 inches to 2 inches. Lightweight interlocking pavers with integral cementitious coating can also be used as the ballast material. The interlocking pavers provide a smoother walking surface and are more aesthetic than the crushed stone, but in general, these ballast systems are not intended for use other than for servicing of buildings.

Extensive roof gardens. These are green roofs that have plants growing in low-profile planting mediums placed over almost the entire roof. Plantings are usually comprised of various types of sedums and hardy wild flowers that are self-sustaining, have shallow root systems, and do not require artificial irrigation. The plants are grown in prepared, shallow soil medium within modular trays that are placed on top of a waterproof roof membrane. Access to and around the roof is provided through small walking paths so these roofs are not designed for extensive foot traffic. They do provide an energy savings as they help to insulate the building. They also reduce the heat effect of traditional dark asphalt or ballasted roof systems.

Intensive green roofs. These roofs are similar to extensive green roofs in that they are comprised of both hardscape and plantings. However, soil depths for plantings on intensive green roofs can range from 8 inches up to several feet. The greater soil medium depth allows intensive green roofs to accommodate a wider variety of plant types and species, including large trees. As these buildings and roof systems are usually designed to accommodate more weight, larger hardscape areas can also be included in the design. With the combination of larger hardscape surface areas and deeper planting areas, intensive green roofs have the potential to provide more outdoor amenities and additional living space on the roof deck.

Pedestal roof systems. These roof systems provide a means of creating a level deck space on top of pitched or uneven roof surfaces that would otherwise not be usable. The pedestal deck systems can also conceal roof extrusions and other obstructions, such as pipes, vents, and anchor points. Pedestal systems allow wood units, stone units, porcelain tiles, natural stone slabs, or concrete slab tiles to be placed on top of a grid of pedestals. For lighter products susceptible to wind uplift, additional fasteners are required to ensure the units stay in place.

Image courtesy of Unilock

Shown is a section of a pedestal roof system.

The placement of the deck surface on a pedestal system also provides space between the deck walking surface and the roof membrane for added insulation as well as room for utilities, such as irrigation lines leading to planting areas. The preferred layout for this type of system is orthogonal. Curvilinear layouts require significantly more pedestals that can increase the cost. The distance between the pedestals can also be constrained by the size and strength of the slabs or panels that they support.

Outdoor amenity roof spaces. The fifth type of roofing system is in high demand, as it provides owners and developers with greater options for providing outdoor amenities in the multifamily and commercial building market. In the past, most outdoor amenity spaces, such as patios, grilling areas, and gardens, for large commercial and residential units were on the ground level. More frequently, these outdoor amenities can now be found on the roof, as developers wish to enhance the marketability of their projects by capitalizing on roof views, while also utilizing roof space that would have previously remained as a mechanical space. Outdoor amenity roof systems need to be more than just open spaces or large expanses of green roofs, as developers are looking for programmed and programmable outdoor amenities that include a wide range of components, such as hardscape patio areas, planting areas, walkways, pet play spaces, fire pits, pools, kitchens, dining and bar spaces, and even putting greens. Real estate market studies have shown that projects offering enhanced outdoor amenity roof spaces may cost more to construct, but they are easier to market, bring in higher rental and sales prices, and retain renters for a longer time frame. The construction of these systems requires careful design and coordination, but developers are seeing potential one-year returns on their investments by including outdoor amenity roof spaces on buildings.

The outdoor amenity space provides the best combination of the intensive roof garden, green roof, and hardscape, while still providing water protection for the roof. These are aesthetically pleasing and functional designed spaces. A local landscape architect can provide the most suitable arrangement of the hardscape and planting balance to achieve harmonious connection to the interior building amenities.

Photo: Tim Benson

Shown is the outdoor amenity roof space at Prudential Plaza, Chicago.

Basic Componoents of Roof Deck Systems

There are primarily three construction systems used for amenity roof applications: the pedestal system, slabs on granular base, and slabs on permeable base. Although these three are the most commonly used, other construction methods, such as mortar set or sand over concrete, are also used in the appropriate applications.

The pedestal system is the most widely used, as it is easy to install and maintain and provides a system for leveling uneven roofs. Pedestal systems, however, have size limitations due to the load limitations, their limited size, and the required spacing of the pedestals. These systems start with the concrete structure of the building over which a waterproof membrane is placed. A protection board is then placed on top of the waterproof membrane, and insulation is placed on top of this protection board. The support pedestals sit on top of the insulation, and the roof slab tiles or units are anchored to the pedestals. Tiles or units can be made of wood, concrete, stone, or porcelain depending on the desired aesthetic. It must be noted that some tile or paver products may require a full base tray to support the product against breakage or cracking as a result of impacts or too heavy loads.

There are three basic types of pedestals: fixed height, adjustable, and stackable. The adjustable pedestal systems are the most commonly used, as they provide the greatest flexibility.

The pedestals are fabricated of a high-density copolymer polypropylene containing 20 percent post-industrial recycled material. They are impervious to water, mold, and freeze/thaw. They can support loads of 1,250 pounds per pedestal. The height adjustment ranges from 2¹/₄ inches up to 36 inches, and the integrated leveler accommodates a 0 to 0.5 inch/foot slope.

Photo courtesy of Unilock

Shown is the pedestal roof system at Fuse Condominium, Cambridge, Massachusetts.

A slab on a granular base is the oldest and most widely used system and is easy to install. There are no size or shape limitations so these roofs can cover large areas. However, slabs on granular base are the most expensive systems to install and can be costly if repairs to the membrane are necessary. The system starts with the building’s concrete slab over which a waterproof membrane is placed. A drainage mat is then placed over the membrane followed by any potential insulation, if required. The drainage mat or roof drain has a geotextile fabric covering to prevent setting bed fines from clogging the drainage area. Roof tiles or pavers are placed on the sand setting bed and held in place with joint sand. Figure 1 provides a typical cross-section view of this type of system. In some newer systems, the insulation is placed on top of the waterproof membrane, providing more protection to the membrane from extreme temperature changes and physical damage.

Photo courtesy of Unilock

This cross section of a slabs on granular base roof system shows sand setting bed with drainage mat and insulation.

A roof system with slabs on permeable base (chips) can accommodate heavier loads than the pedestal systems. This system also provides optimum drainage, as the permeable chips or aggregates maximize water penetration. The construction for this system is shown in Figure 2 and consists of the building’s concrete structure, a waterproof membrane, insulation, a permeable setting bed and base, and finished with the roof slab tiles or unit pavers.

Image courtesy of Unilock

Shown is a cross section of a slabs on permeable chips roof system.

Existing wood roof structures can also be retrofitted with a roof deck system by adding a structural underlayment to the existing joist and beam structure. Spacer tabs of ¹/₈-inch thickness are set on the structural underlayment, and the roof tile units (porcelain, stone, concrete) are anchored on top.

Whether the slabs are set on a permeable base roof system or on a pedestal system, this top surface of the roof is still “permeable.” However, all of the above systems use a waterproof membrane in their construction to keep water from penetrating through the roof into the building.

There are opportunities and limitations with each paving system. With the elevated roof slabs on pedestals, utilities can be hidden under the slabs and allow easy access to roof drains and other maintenance. For some buildings, a pedestal system can be a very economical way to transform any exterior roof space. The main limitation of elevated pedestal slab systems is regarding layout. The most efficient size is on a 24-inch grid. However, this grid reduces the design flexibility. In contrast, the sand set and permeable over granular base systems allow for a more dramatic use of material sizes, shapes, and layouts. These systems expand the landscape architects creative abilities to work off the grid by designing more natural, curvilinear spaces. Certainly, with base material comes an increased cost, but the weight per square foot can also be a limiting factor. Confirming the structural loads is an essential step in the design process.

All three of these roof decking systems help to provide added insulation to the building’s interior spaces. With the added layers of these roof decking systems, building interiors remain cooler in summer and warmer in winter, thus providing energy savings.

Hardscaping Products for Roof Deck Systems

There are four popular products used as slab or paver units in roof deck systems, and these products provide designers with a range of colors, sizes, and finishes for roof deck surfaces.

Concrete slab tiles provide a range of sizes, colors, and finishes. They range in price from $3.50 to $11 per square foot depending on the size and finish. Concrete slab tiles must meet ASTM C1782, which is the standard specification for utility segmental concrete paving slabs. The primary method for determining suitability for spanning between two pedestals spaced 24 inches apart is the product’s flexural strength, measured by its modulus of rupture, which places a load in the center of a slab supported only on the corners. According to ASTM C1782, a product in this application support a minimum load of 650 psi. In addition, they must comply with ASTM C1645 for freeze-thaw durability and ASTM C418 for abrasion durability. For pavers set on a granular base and are 101 square inches or less, they need to meet ASTM C936: Standard Specification for Solid Concrete Paving Units.

The concrete slab tiles have quality controls that limit the modulus of rupture to an average of 725 psi. Modulus of rupture indicates the flexural strength or bending strength of the concrete. Concrete slab height tolerances are allowed to +/- 3 mm. The height tolerance ensures uniformity to the slabs and makes the installation easier, as the uniform height or thickness means less time is required during installation. The weight of these concrete slab tiles varies depending on the slab thickness. Units that are 1³/₄ inches thick weigh 19 pounds per square foot. Units that are 2 inches thick weigh 22 pounds per square foot. Units that are 2³/₄ inches thick weigh 31 pounds per square foot. Units that are 4 inches thick weigh 46 pounds per square foot.

Concrete slab tiles and pavers can be manufactured in the standard ‘thru-mix’ where the same aggregates are used throughout the slab. The only drawback is that over time, the concrete and pigment will wear, showing the large aggregate at the surface, and appear faded and worn. A newer two-step manufacturing process combines a base of coarser aggregates for high strength and durability, while concentrated color and wear-resistant finer aggregates form the top. This results in a surface that is almost fade proof and UV resistant.

The aesthetic options for concrete slab tiles and pavers include multiple surface finishes of standard, smooth, brushed, exposed aggregate, blasted, speckled, and mottled. Concrete slab tiles can be both wet-cast and dry-cast depending on the style. Two recently developed concrete slab tiles provide an exposed granite blasted finish and a flamed finish. These newer tiles use a process that is more like wet cast, only the water is squeezed out. These tiles and pavers can also be treated with an easy-to-clean, stain-resistant finish during the manufacturing process, eliminating or reducing the need to use aftermarket sealers.

Photo: Essi Ala-Kokko Photography

A system of concrete pavers and slabs on permeable base is used at 233 N. Michigan Ave., Chicago.

While slabs or tiles have more commonly been used in roof deck environments, traditional concrete unit pavers that are used on the ground are gaining popularity in roof deck spaces. This allows designers to further extend their creativity and create continuity from the ground level to the amenity spaces, while enhancing the flow, patterning, privacy, and division of amenity spaces. These pavers were used on the Hullmark project in North York, Ontario, Canada, and Fuse Condominium in Cambridge, Massachusetts.

Natural stone tiles for amenity spaces are available in three classification categories: igneous, metamorphic, and sedimentary. With each classification, there are a variety of stone options, with the most popular being granite, sandstones, and limestones. Many are available in a range of colors and textures as well as sizes. Natural Stone pricing can range from $8 to $44 per square foot depending on the stone variety, finish, and thickness.

Finishes include polished, honed, water jet, sandblasted, leathered, flamed, combed, riven, and antiqued. Sizes range from 12 inches by 24 inches up to 24 inches by 36 inches. Natural stone tiles are available cut into natural edge steps, natural edge copings, full nose copings, and stone pillar caps.

Stone thickness ranges from ⁷/₈ inch to 2¹/₂ inches or thicker if necessary. This low-profile thickness makes it well suited for many applications but in particular for a concrete or wooden deck overlay where there are constraints on the height or weight of the material. The thickness will be determined by the span of the stone between supports if not placed on grade. For granite materials, the Marble Institute of America recommends a minimum flexural strength of 1,200 psi per ASTM C880 with compressible strength of 19,000 psi per ASTM C170.

Sources for natural stone include countries in Asia such as India where you may wish to validate the ethical standards of the quarry. There are suppliers in North America aligned with quarries that only process to the strict standards of ethical trading initiatives, ensuring that no child labor is used, fair wages are paid, and safe working conditions are maintained. Quarried stone varieties from India and other countries in Asia, North America, South America, and Europe include sandstone, limestone, granite, basalt, and quartzite.

Photo courtesy of Unilock

Natural stone is used as a roof deck walking surface at a private residence in Chicago.

Porcelain tiles also provide a wide selection of colors and finishes. They are available in a variety of sizes, however, three sizes are commonly used for roof decks: a 24-inch by 24-inch square, 16-inch by 48-inch rectangle, and a 16-inch by 32-inch rectangle. The porcelain tiles are also uniformly thick at ⁵/₈ inch, and this low profile makes them ideally suited as overlay products, particularly where installations have height or weight constraints. The tiles can be used as an overlay application on new and existing concrete decks, porches, balconies, stairs, and wood decks. Finishes include stone finish, and wood grain finish and edge treatments can be specified as sawn or pressed. Pressed edge (other names include cushion edge, round edge, and soft edge) tiles have been manufactured using standard pressing processes in molds that result in a slight curving on the sides. The amount of curving will vary between manufacturers and processes. First quality tiles with pressed edges have batches with an allowable variation in size. Thus, a wider grout joint should be used to allow for this tile size variation.

Porcelain tiles meet the following standards: ASTM C373 for water absorption (which is very low), ASTM C1026 for freeze thaw, ASTM C648 for breaking strength, and ANSI A137.1 for slip resistance. Porcelain tiles are designed for pedestrian use only but are ideal for commercial applications. The colors are non-fading for long-term wear performance. They are priced on average about $8 per square foot. Porcelain tile is manufactured worldwide. The tiles are manufactured to size and well packaged to protect them during shipment. Porcelain tile and natural stone may, in some cases, require additional securing to prevent against wind uplift.

Wood decking units or panels are usually square and have minimal size variations. Structural wood tiles are available to provide decking on roofs where designers are looking for a different texture. Wood tiles or panels can be fabricated from foreign woods, such as ipe, cumaru, and garapa. It is important to make sure that these products are harvested using environmentally responsible methods designed to preserve rainforest hardwoods or are certified by the Forest Stewardship Council (FSC). Wood tiles can also come from thermally modified North American hardwoods. Wood decking panels have hardiness ratings ranging from 1,630 to 3,680. They come in two sizes: nominal 24-inch square panels that weigh 24 pounds and nominal 24-inch by 48-inch rectangular panels that weigh 48 pounds. All wood panels have a Class A fire rating. Pricing ranges from $12 to $14 per square foot. Even though these products resist fire, some restrictions may apply with local fire building codes.

The thermally modified North American hardwoods are domestically sourced from red oak and ash trees that are currently harvested in Wisconsin. Red oak and ash are the preferred species because of their consistency in durability and color. The natural durability of the red oak and ash is enhanced through the thermal heating process, creating a product that is a Grade A wood with a 25-year Class 1 durability level and a resistance to decay that is comparable to South American hardwoods.

The variety of available tiles for roof deck systems provides designers with a broad palette of materials in designing urban outdoor spaces for roofs. The variety of products to create amenities on building roofs extends vertically as well as horizontally.

These various surface treatments, wood decking, stone tiles, porcelain tiles, and concrete pavers are all materials that meet LEED criteria. Porcelain tiles, stone tiles, and concrete pavers can be obtained regionally. All of these surface materials have much higher reflectivity than standard black roofs, thus providing higher solar reflective indexes (SRI) for compliance with the International Green Construction Code (IGCC) and reducing heat island effect.

Wall Systems for Outdoor Urban Environments

Adding vertical elements into the outdoor amenity space will enhance the aesthetic of the space. Instead of a waist-high handrail separating the user from the building edge, seat walls and plant material are used to buffer the edges of the space. A creative design uses these vertical elements to create semi-private spaces on the amenity roof. Larger trees provide shade and wind blocking in some cases. Smaller shrubs, grasses, and perennials enhance and focus views toward adjacent desirable site lines for bodies of water and sunsets, while screening undesirable views and building glare.

With the demand for a greater variety of outdoor amenities on urban roof systems, segmental interlocking wall systems are available to create raised planters, seat walls, and privacy screens. These wall systems are comprised of segmental block units that are available in a range of sizes and styles from contemporary linear to a more traditional dry stack and a variety of textures and colors, thus providing designers with a broad palette of materials.

Most wall systems are heavier than pavers and fit the weight requirements to counter wind uplift. Some wall systems are hollow, however, the majority of wall systems use solid units, as these units provide a more stable wall system. Many hollow walls require a back fill of granular or rebar and concrete. This increases the labor component on the project. Solid walls reduce the extra labor.

Photo courtesy of Unilock

Wall systems are used to create seat walls and planters at Hubbard Place, Chicago.

Summary

With the continued growth in both residential and commercial developments in urban centers, the demand for outdoor urban amenity spaces will not only continue but will be expected. And with the variety of products and systems available, the sky is the limit in terms of the design possibilities for outdoor amenities for roof deck projects.

The following case studies of residential and and commercial roof garden and deck projects illustrate various methods for meeting LEED criteria. Energy use is reduced in buildings with roof gardens and outdoor amenity spaces. The lighter colors of the roof deck surfacing and the vegetated areas reflect heat better than traditional black roofs. The vegetated areas also assist in the management of stormwater runoff from the roof as they absorb water. As much of the material (vegetation and hardscape surfaces) can be obtained locally, the LEED criteria for use of regional materials can be met.

RESIDENTIAL CONDOMINIUM ROOF GARDENS

Residential condominium roof gardens can utilize a variety of roof systems in their construction. The following are some examples of successful designs that incorporate a number of different site amenities within the roof deck space.

The Illinois Center Plaza’s south section has undergone a series of innovative architectural changes to its roof deck space located at 233 N. Michigan Ave. Wolff Landscape Architecture Inc. of Illinois designed a roof deck space with built-in benches, flower beds, tables and recliner chairs, and a centrally placed green space. The roof deck is in the center of residential and commercial building units.

This is a high-traffic pedestrian plaza that needs to be extremely durable and also permeable. The square concrete slab tiles and pavers were used in combination with permeable spacers to meet both pedestrian traffic demands and the need for permeability. A slab on permeable base roof system was used for construction. The paver colors were selected to complement the building structure and its surroundings with a mottled finish that looks like granite and includes a treatment added during the manufacturing process that makes them easier to clean and maintain.

Located in the River North neighborhood of Chicago, the Hubbard Place roof deck provides occupants with an inviting atmosphere that includes comfortable seating areas, private outdoor grills for solitary dinners or large group parties, outdoor fire pit, sundeck, a dive-in pool, landscaped dog run, and a variety of garden spaces, all with stunning city views. The designer was Daniel Weinbach & Partners, who constructed the roof deck using a variety of concrete pavers and slabs with exposed washed aggregate and mottled granite-like finished in different colors used to delineate spaces and flow. Concrete segmental blocks were used for seat walls and garden walls, which effectively created private spaces for residents and their guests.

Photo courtesy of Unilock

Shown is the roof deck at Hullmark Centre, North York, Ontario, Canada.

Hullmark Centre is a signature condominium development in North York, Ontario, Canada. The development includes a prime office component, premium retail spaces fronting onto a public plaza, and the tallest condominium towers to in the North York skyline.

The outdoor roof terrace includes a swimming pool, cabana, pavilion garden, fireplace, and barbequing stations. The designers at MBTW Group used concrete pavers to unite the surroundings. This design uses semi-private settings rather than one large open-concept roof deck. The second-floor amenity space is an urban oasis with lush landscape planting to complement the numerous amenities, which include a 150-foot-long trellis that bisects the amenity area and connects several small seating niches to the exterior fireplace and lounge, acting as the focal point at the terminus of this feature. The exterior spaces of the podium are unified by a common palette of materials that include aluminum and stainless steel, granite, limestone, and patterned unit paving. The predominant product on the amenity terrace is 70-millimeter-thick concrete pavers in granite blend and dark charcoal colors in a variety of sizes. Black granite color concrete pavers were used as accent banding.

The Fuse Condominium project in Cambridge, Massachusetts, set out to create an outdoor living room or public backyard for the residential community. “Residents in urban settings strive to find a balance between the excitement of the city and the vast social opportunities, while trying to carve out a little serenity and relationship to nature/seasons/etc.,” says Robert Adams of Halvorson Design Partnership.

The courtyards and open spaces in this residential community provide many desired qualities of life: sunshine, nature, social spaces, etc. There are two roof amenity spaces on this project designed to provide a variety of different scaled spaces to appeal to a variety of users and uses. One has a pool, lounging, dining area, and conversational zones created with pergola-type structures and furniture groupings. This space used a 24-inch by 24-inch concrete slab and wood deck tiles on pedestal to create a harmonious and beautiful design. The second space has a large green area with medium-sized patios and dining rooms with grills, tables, chairs, and side tables, with intimate spaces tucked into the edges of the large central lawn. Using the same traditional permeable pavers that were used on the ground level, the designer was able to continue the hip and energizing paver design in this amenity space over a permeable base. Both spaces borrowed from the surrounding Alewife Reservation, utilizing a glass railing to make the edge as porous as possible and using the same plant types found in the borrowed landscape to tie them together.

Robert points out that “creating open space that provides social interaction at a variety of scales and activities, open space that connects to the context/larger natural environment, and open spaces that somehow enhance the seasons/natural systems” was essential on this project.

COMMERCIAL ROOF GARDENS AND DECKS

Successful commercial roof gardens utilize a variety of roof deck systems and roof tiles. Located in the Financial District of Boston, One Federal is a skyscraper that is noted for its outstanding height of 38 floors. Architects CRJA-IBI Group worked with the project architects to improve the existing underutilized roof top garden space on top of the ninth floor. The goal of this renovation effort was to create a usable indoor/outdoor space for the tenants of this office building. The outdoor space was redesigned to accommodate a variety of programmable uses, including casual lunch gatherings, awards ceremonies, cocktail parties, and weddings. The landscape architects used a square concrete slab paver to meet the design requirements. Varied colors in a mottled finish that looks like granite were used to detail the building entrance. Colors were selected for their low solar reflectance value and to complement the greenscape and water features. As part of the manufacturing process, an additive was included for surface protection that will make the area easier to clean and maintain.

This roof deck utilizes a pedestal installation. Structural evaluation of the existing concrete deck was undertaken to determine its load-bearing capacity for new landscape elements that included new paving, walls, curbs, planting loam, and plantings. The existing drainage system was evaluated by an MEP engineer to ensure that modifications/replacement could occur simultaneously with landscape enhancements.

To achieve these flexible garden uses, the final design provides for universal access, a large open space for gathering, pedestrian scale paving zones, and a strong, simple planting palette that can be easily maintained.

Photo courtesy of Unilock

The roof deck at One Federal in Boston was designed by CRJA-IBI.

Prudential Plaza in Chicago presents an elevated project with amenities that include a lounge space with a fire pit, an outdoor bar area, and views of Lake Michigan and Michigan Avenue. Wolff Landscape Architects used 2,300 square feet of custom concrete slabs for this roof deck. The design balances the landscape and hardscape elements to create an oasis in the heart of Chicago.

Photo courtesy of Unilock

Loews Chicago Hotel is the city’s largest outdoor rooftop terrace.

Another Chicago roof deck project is at the Loews Chicago Hotel, which was constructed in 2015 and also designed by Wolff Landscape Architecture. This project has two expansive rooftop spaces, one a pool deck amenity and the other a social and entertaining space that includes two restaurants. This outdoor amenity roof deck includes a grassy lawn areas for lounging or games, planting areas with seasonal floral and greenery, a two-level terraced areas, and cabanas, providing guests and visitors with views of the downtown and the lake in a park-like setting. This roof was installed on a pedestal system, and has 24-by-24 square concrete slab pavers in two shades that cover over 18,000 square feet of pedestrian terraces.

RESOURCES

Protected Membrane Roof Guidelines. The Dow Chemical Company. Web. 23 March 2017.

Elena M. Pascarella, RLA, ASLA, is a practicing landscape architect, continuing education presenter, and consultant engaged in a private practice based in Rhode Island. The firm’s portfolio can be viewed at www.landscapeelementsllc.com.

Designers and architects trust Unilock pavers and retaining walls to achieve their vision without having to compromise either creative design or long-term performance. We introduced pavers to North America, and we continue to deliver on style with the latest technologies. commercial.unilock.com