On The Edge Of Spectacular

The earliest documented swimming pools include the “Great Bath” at Mohenjo-Daro, now Pakistan, pools built for military and athletic training by the ancient Greeks, and the famous Roman baths, built during the occupation of Britain by Emperor Claudius to stabilize and enclose the natural hot springs below.

Rooftop pools have become increasingly popular. Photo By Mahan Rykiel Associates

Pools have been a part of human civilization since the 3rd millennium B.C. Modern swimming pools began to appear in Britain as swimming clubs became popular in the mid-19th century. The concept expanded worldwide when the Olympic Games restarted in 1896 and included swimming races.

Today, pools of every size, shape, color, and purpose are ubiquitous. Private, residential pools can be found in every corner of the globe and in every climate. Schools, health clubs, recreation centers, hotels, and now even some hospitals seem incomplete without a pool of some type.

Why Build On The Roof?

As land becomes scarce in congested urban areas, pools are becoming more common as rooftop amenities. Hotels and urban residential developments are looking at rooftop pools as a way to differentiate themselves from the competition.

A quick Internet image search will reveal pools with transparent bottoms and sides, pools with infinity edges that merge with the skyline, and pools that jut precariously beyond the roof.

Walk-in edges, chaise-lounge ledges, and pools that double as decorative fountains are some of the new and exotic elements of the traditional pool.

With new building techniques, non-chemical filtration, affordable heating equipment, automatic covers, and other advances in construction, operations, and maintenance, rooftop pools are becoming more realistic options.

Their value as an important amenity and point of differentiation can be seen in the competition among Las Vegas hotels to outdo one another with the latest fantastic pool environments. They become focal points for events and activities both day and night, in addition to their historical role as a recreation amenity.

A pool can enhance the value of a small space, adding a sense of life, color, and movement. It can reflect the sky during the day and, with an infinity edge, visually extend the smallest space out to the horizon. At night, as a shimmering light source, a pool can transform the character of a garden and turn it into a magical place.

Also, as a result of the development world continuing to embrace green technology, rooftop gardens are becoming an attractive opportunity to meet sustainability goals. They can help reduce building operational costs, enhance value for real estate, and meet increasing government demands for less environmental impact, particularly for the capture, filtering, and reuse of stormwater runoff.

The Challenges

Maximizing Space: Most roofs by definition are space-challenged. Getting the most benefit often depends on the population being accommodated. For residential projects for a smaller population, pools can become the focal point for a garden and a place of refuge, as much as a recreation space. In these situations, the landscape may be as important, or more so, than the pool.

Hotels must plan for times when the deck is full with guests. Space for enough seating and lounges is a critical design issue for a successful guest experience. The pools themselves need to address a wider user base--children, casual dippers, sunbathers, and swimmers. Food and beverage are often part of the mix at larger pool decks, and these facilities need to be factored into the design. Separate restroom and changing facilities quite often are necessary.

This rooftop pool in San Juan, Puerto Rico, is a popular amenity. Photo By RTKL / David Whitcomb

The rooftop can be a highly desirable, programmable space that enables the operator to host a variety of income-producing entertainment activities, particularly at night.

Pools at the edge of the roof can free up space for a variety of other guest and event activities. The popular infinity edge creates visual drama, and borrows space from the view beyond.

Many pools can be designed to double as fountains, adding sound, light, and movement to enliven the space.

“All pools leak:” So says Trip Knox of International Aquatic Design, a Massachusetts-based pool-design, fabrication, and installation firm. “Pipes move, concrete cracks, finishes wear out, or the pools just sweat from condensation.”

Eventually, even the most carefully constructed pool will leak. This may not always involve the primary containment vessel, but may involve piping, connections, or drains.

For in-ground installations, this is not usually a major problem. But for pools situated above occupied spaces in a hotel or residential development, it can be extremely damaging, disruptive, and costly to repair.

For hotels in particular, which tend toward larger pool installations, this is a major concern. Bigger pools, more weight, and more plumbing invite more opportunities for something to go wrong.

Providing enough space for a meaningful guest amenity typically means using the larger spans associated with a hotel’s public spaces and function areas (i.e., lobbies, meeting-room complexes, and ballroom ceilings). Shutting these down to fix a leaky pool can be disastrously expensive.

Almost all rooftop pools should provide secondary containment as a precaution, creating essentially a pool within a pool with the necessary supporting drainage systems.

A technique quickly gaining favor is fabricating the primary containment vessel in stainless steel as a single unit (or with larger pools, several large pieces that can be lifted into place and welded together), thus significantly reducing the likelihood of future leakage from the pool itself.

These pools are lighter, potentially reducing structural requirements in some cases; provide a higher level of quality control since they are built off-site; and often offset the higher initial cost with simpler and less time-consuming installation at the job site. They can be finished in the same way as with traditional concrete pools.

Wind on the water: Wind is a consideration when designing pools with infinity edges or raised zero edges. In conventional pool designs, where the final water level is recessed 8 to 12 inches below the deck surface, the effects of high winds across the water surface are usually limited to waves occasionally cresting the coping and splashing water onto the deck.

With flush-edge conditions, the increased wave action brought on by high winds can push much larger quantities of water onto the surrounding deck surface. While this typically isn’t a concern where the pool is set back from the edge of the building, it is a point to consider when infinity-edge pools are placed in close proximity to the parapet.

To counteract the sometimes negative effects of this action, it is advisable to install controls that allow the water levels within the pools to be monitored and quickly modified.

At the Four Seasons Hotel in Baltimore, Md., guests are afforded three pool experiences. The fourth-floor feature pool is a raised-edge infinity pool that doubles as a water feature when not in use. An 18-inch granite-clad wall surrounds the pool entirely, and a bull-nosed edge allows water to slip smoothly across its top and down the wall face.

To catch and return water to the pump room, a 12-inch (W) by 9-inch (D) trough was designed at the base of the pool, concealed neatly by slotted, cantilevered stone pavers carrying the required depth and "No Diving” markers.

The fifth-floor amenity space consists of a hot tub with the same raised-edge concept as at the feature pool and a wet deck--a 3-inch beach-entry reflecting pool, which allows for a more subtle interaction with the water.

This wet deck concept is gaining traction in rooftop applications, as it is a much lighter and significantly cheaper construction type. Here, 12 inches of water depth are being accommodated, as opposed to the 36-inch to 60-inch depths found in a typical pool. Interaction is limited to walking through, standing, or sitting in the water, but the sleek, contemporary appeal of the feature in many cases offsets the fact that it doesn’t fulfill the function of a standard swimming pool.

The benefit of having an amenity that doubles as both a static water feature and an interactive pool, coupled with a significantly lower price point, makes the wet deck an extremely attractive element to developers.

The supporting cast: Filtration, make-up reservoirs, and plumbing are often afterthoughts for designers, whose primary concern is creating a sexy pool and a great guest experience.

On the ground, these systems can be straightforward and easily hidden behind fencing or landscaping. On limited and precious roof space, this issue can become more challenging. Finding a workable location for this equipment, a place that can be accessed easily for maintenance and repair, often means using valuable floor area within the building, or in the difficult-to-reach leftover spaces below the pool deck and above occupied spaces.

The cost issue: Size, type, location, structural implications, access, finishes, and landscape treatments will all be factors an owner-operator must consider.

Can the space become more than a necessary loss-leader that guests have come to expect? Or can it instead be a profit center--one that can host its own unique events and can also support the hotel’s food, beverage, and meeting businesses?

To maximize the amenity, the pool designer should consider the multi-use potential of the deck at the beginning of the process. This process should include the operator, and take into account critical aspects, such as spatial flexibility, that can adapt to a variety of uses; adjustable lighting; the ability to support electrical and audio-visual capabilities; and storage for furniture changeovers (lounge chairs to four tops, for instance).

Well-designed and attractive pool environments have demonstrated their ability to help define and differentiate a property from the competition.

Bob Gorman, FASLA, is a Principal at Mahan Rykiel Associates. For more information, contact Bob for hospitality or resort projects through the marketing department at Mahan Rykiel Associates at 410-235-6001 or by email at mra@mahanrykiel.com. For other examples of our hospitality portfolio, visit www.mahanrykiel.com .


On The Edge

The pool deck at the Puerto Rico Convention Center Sheraton

With limited space and a program for the headquarters hotel virtually filling the site, the only option for the pool location was four levels above the street and over the ballroom. At nearly 2 acres in size, the deck was more than large enough to accommodate a multi-faceted program of spaces and uses.

However, the ballroom below took up almost two-thirds of the area, leaving little space between its ceiling and the roof deck with enough depth to accommodate the pool.

Lifting the pool above the finished deck was an option, but the adjacent tower had rooms designed to have terraces at the same level as the roof deck, so this opportunity was somewhat limited. In the end, the edge away from the rooms allowed for some lifting of the pool, and added depth beyond the ballroom space below.

The stainless-steel tank was fabricated off-site and lifted into place in several sections to create the 125-foot-long main pool. Over the ballroom, where depth is limited, a lounge ledge fills this restricted space with an amenity that guests enjoy--space for sunbathing in the shallow water.

By slightly raising the deck around the pool, an infinity-effect was created, and protective safety rails were kept out of sight below eye level.