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Conceived of as part of the home’s original design and construction, this stunning rectangular pool provided the watershaping team of William Bennett and Walter Williams with the opportunity to work closely with an architect at the top of his game. The resulting composition in concrete, glass, wood and water – set on a steep slope in a densely wooded area – made all participants to rise to the occasion with practical, cost-sensitive solutions.
Conceived of as part of the home’s original design and construction, this stunning rectangular pool provided the watershaping team of William Bennett and Walter Williams with the opportunity to work closely with an architect at the top of his game.  The resulting composition in concrete, glass, wood and water – set on a steep slope in a densely wooded area – made all participants to rise to the occasion with practical, cost-sensitive solutions.
By William Bennett & Walter Williams

There’s no doubt about it:  Projects in which watershapers participate from the start in the overall design of a custom residence offer rare opportunities for creative integration that don’t come along very often.  That was just the positive situation we encountered here – and the results are among the finest we’ve ever achieved.

The project was organized by Lewis Bloom of Bloom Builders (Bethesda, Md.).  We at Alpine Pool & Design (Annandale, Va.) have had the privilege of collaborating with him often through the past 20 years and have enjoyed a wonderful working relationship every step of the way.  In this case, we were asked to get involved with a spec house he wanted to build on a steeply sloping, heavily wooded lot overlooking the Potomac River as it passes through Bethesda.     

Heading the design team was a prominent local architect, Robert M. Gurney, who has earned a reputation for beautiful Contemporary approaches to both residential and commercial projects.  More to the point, he’s also known for his ability to maximize connections between built spaces and the areas that surround them.

Everything seemed to mesh, and we jumped in without hesitation.


The preliminary design wasn’t in a style typically associated with the area, but Gurney won everyone over by making his tall, angular structure seem right at home in its rustic environs.  The key in this case was his extensive use of Ipé in conjunction with the glass and concrete:  Its warm wood tones struck a natural balance between the stark geometry and the home’s wooded surroundings.

What he also wanted was a visual bridge from structure to surroundings in the form of a large, reflective water surface – and that’s where we came in.  We went to work immediately, collaborating with the structural engineers to achieve complete visual integration of home, water and the environment beyond.  

The home itself now stands three stories above grade, which places the outside edge of the pool a full 25 feet above ground level.  From inside the house with its floor-to-ceiling glass wall, it always seems as though you’re among the trees.  In fact, many people have described the space as an astonishingly luxurious treehouse.

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The structure supporting the pool is basically a table stretched across six walls running perpendicular to the house and its foundation.  One of the open bays this system created became our equipment room, while up on top we prepared a box that would eventually contain a pool that was to be built within it.
In aesthetic terms, the home’s design is extremely straightforward, so the decision to complement it with a simple, rectangular pool was a natural.  At first, we tried to up the ante by nudging Bloom to go with a vanishing-edge design that would have broken the barrier between home and woods and tied the entire prospect into views of the river.

That didn’t work out, however, with Bloom convinced that working so far above grade with such an elaborate detail would’ve added another layer of complexity that just seemed too costly.  (The idea stuck, however, because in another project we’re just starting with him in similar circumstances, a vanishing edge is very much in the picture.)

The ten-by-55-foot pool for this project is four feet deep on both ends, sloping gently to a center depth of five feet.  The pool is separated from the home’s glass wall by a six-and-a-half-foot-wide strip of wooden decking – fairly tight, but enough distance that you don’t feel as though you’re going to fall into the water when you step outside.  

To be sure, it’s a narrow space – yet another decision driven by economics:  The farther out we reached from the back of the house, the taller and more massive (and costly) the support structure beneath it would have to be.  There’s also the fact that two spacious deck areas are available at both ends of the pool, with a primary space defined at one end by a long fire feature.  Taken all together, this pool/deck area is 88 feet long, spanning the entire width of the house, and about 20 feet wide.


The obvious challenge with this project was elevating the pool and deck structure 25 feet above grade.  We’ve completed a number of above-grade structures through the years, using a variety of approaches that have most often included columns of some sort.  In this case, the builder wanted something different – structurally sound, of course, but also more cost effective than other strategies.

Simply put, the design team decided to install a concrete “table” that would serve as the bottom of the pool structure and support the shell.  To complete it, the builder installed six reinforced, concrete-masonry-unit (CMU) walls perpendicular to the back of the house and spanning a bit more than the width of the pool/deck area.  

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Once the box was ready, we lined it with foam panels and plastic to ensure that the pool could expand, contract and move independent of the supporting structure.  Once the plumbing was set (no small trick given the space restrictions), we shot the pool and basically hid any signs of the box beneath it.
This approach was feasible because the entire house was set on standard concrete footings that reached down to competent, load-bearing soil.  The footings we were to add for the pool and deck were similarly just a few feet deep, but we made them a robust five feet wide to forestall any lateral movement.  In addition, the builder cross-linked the perpendicular walls, further enhancing lateral stability.

To create the tabletop, Bloom turned to a local manufacturer of prefabricated concrete slabs of the sort used in parking garages.  These slabs are three feet wide and a foot thick and were specified to span the supporting wall system.  When construction was under way, these panels were delivered, craned into place and then mounted on top of the walls to give us the platform we needed to build the pool.

Our first step involved the fashioning of a reinforced CMU box within which we’d eventually place the pool shell.  To ensure that the gunite shell we’d be adding could expand, contract and move independent of the box, we lined the walls with polyurethane foam and covered the floor with two layers of six-mil plastic sheeting. This plastic allows the gunite structure to shrink onto itself while the foam accommodates extremely minute differential movement between the box and the pool structure.

The basic structure we were working on was so sound that our concern was never ground movement; rather, we were concerned about creating a situation in which the box and shell would move differentially and might actually grind one another to pieces.  The approach we developed to isolate these structures from one another was like creating a gigantic foam ice chest.

Once the box was ready, we set the pool-floor contours with poured concrete, similar in effect to what might be done with crushed rock beneath a common inground pool.  From that point forward, pool construction became somewhat standard – almost.


The trickiest part of the project once the box was done had to do with establishing the plumbing runs, mostly because we didn’t have much room.  First off, everything had to be accessed through the inside wall of the pool.  In addition, in some places we had to cut holes or channels in the foam and polyurethane to accommodate runs from the pool to the equipment pad, which we placed in a space directly below the center of the swimming pool.  

Up and Under

As mentioned in the accompanying text, the equipment pad for this pool sits several feet below its center – a decision made by the architect’s structural engineers.  

It makes sense, because the system of walls they devised to support the structural-concrete “tabletop” upon which we were to build the pool created an enclosed box that was perfectly suited to the task.  We completed the room by pouring a slab between the support walls’ footers, ultimately creating a tight but workable 12-by-12-foot space.  The room is accessed via an exterior door found on a path meandering down from the house.

Our firm’s service division will service the pool, so we brought in our technicians during the installation process to make certain everything would be as functional and accessible as possible.  The biggest technical challenge we faced had to do with the fact that the equipment is set approximately 15 feet below the bottom of the pool:  We did all we could (within reason) to accommodate the hydrostatic loads as well as the need to winterize the pool.

The lines for the skimmers and the return lines enter through the wall on the house side of the equipment room.  Much of the plumbing was strapped beneath the Ipe deck by our crews, who worked at the top of extension ladders.  We located shut-off valves on all lines so that water flowing in and out of the equipment could be isolated – necessary because of the force of gravity involved in such a drop.

Up above, the lines for the skimmer loop just above the water line.  This makes it possible, when the time comes to winterize the pool, for technicians to blow the lines clear and cap the skimmers.  The arrangement also allows us to isolate the flow from the pool:  With an assist from several check valves, we’ve made the system as safe and serviceable as possible.

The equipment set itself is quite straightforward, including diatomaceous-earth filters and a Whisperflo high-head pump from Pentair Water Pool & Spa (Sanford, N.C.) along with a high-efficiency gas heater from Raypak (Oxnard, Calif.).  For easy maintenance, the system also includes a Polaris automatic pool cleaner and pump made by Zodiac Pool Systems (Vista, Calif.).  

-- W.B. & W.W.

We had to be very careful in all of this because we didn’t want the plumbing to take up space inside the seven-inch-thick gunite walls.  Once we’d figured everything out, we laid and tied the steel – #4 rebar on eight-inch centers – and shot the pool just as we would a normal inground pool.  As designed, the bond beam rises above and wraps over the top of the CMU box, which effectively disappeared from view as the shoot progressed.

Inside the pool, we set up 18-inch-wide steps/benches that run along the side of the pool nearest the home – a detail we borrowed from Frank Lloyd Wright.  On this same wall, we placed four 100-watt lights that face away from the primary viewpoints inside the house.  These fixtures are small and create subtle spotlight effects without causing glare.

By the time we completed this basic construction work and the shell was done, the builder had mostly completed the house.  This complicated things for us to an extent, because we had to use extreme caution in moving our materials through the house to avoid doing any damage.   

One of our first tasks with the shell in place involved installing the deck.  The choice of Ipé was perfect because, as mentioned before, it ties into some of the exterior details of the home while creating a visual link to the woods beyond.  This material also had some practical advantages in being strong, yet lightweight.  This meant that it didn’t need further structural support and was also easy to transport and set in place.

We started around the pool and worked outward toward both ends of the deck space.  The only difficulty came in the fact that we were so high above grade in so narrow a space that it was a bit nerve-wracking for our crews.

The pool has an automatic cover from Aquamatic Cover Systems (Gilroy, Calif.) that features an encapsulated-track system positioned on top of the beam and just below the Bluestone coping.  (An open-track system would’ve required a three-inch coping cantilever:  With a pool this narrow, we didn’t want to lose so much space!)  The cover’s vault is located beneath Bluestone panels set between the fire pit and the pool.  With the exception of a very narrow slot beneath the coping, the system is basically invisible.

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The surface of the pool now reflects the spectacular beauty of the setting, the sleek architecture of the home and the dancing flames of the long fire feature we inserted at the end of the pool nearest the largest available expanse of deck.  It’s a visual delight, day and night – and a source of great pride.
The coping itself is a blue Pennsylvania flagstone that came in 36-inch-long segments that were 18 inches wide – a breadth dictated by the combined width of the pool wall, the slip/expansion joint material and the masonry box.  The stone is two inches thick and was cut to precise dimensions by the stone supplier, who also applied a flamed finish to create a smooth, uniform matte appearance.

The pool interior is a simple, gray-tinted plaster.  We tried to talk the builder into a pebble finish, but he likes gray plaster and has told us he doesn’t mind its inevitably mottled look.  We have to agree that it looks great and that its dark tones support truly amazing reflections.


The final touch we added to the project came by way of the fire feature we installed at the end of the pool adjacent to the cover’s vault.  It’s two feet wide and 12 feet long and was included to add visual drama as well as interesting reflections.  

At first we didn’t give too much thought to the fact that it would also generate heat.  That changed one night after the project was complete and we were having dinner with Bloom on the deck next to the fire:  It was a cool fall evening – probably not more than 50 degrees – but we were all perfectly comfortable outdoors.

After all of the work on site was complete, Bloom and his wife moved into the house and fell in love with it.  As it turned out, however, their stay was short, because the house sold almost as soon as they put it on the market to a buyer who made a generous offer after just one visit.

Little wonder there, because the home is something special – and its elegant watershape a point of pride we’ll carry with us forever.


William Bennett is co-founder and general manager of Alpine Pool & Design Corp., a custom watershaping firm based in Annandale,Va. He has worked in the pool and spa industry in the greater Washington,D.C., area for nearly 30 years, functioning in a variety of construction and management capacities.  He founded his current firm with Walter Williams in 1987, responding to the impression that the market in their area was ripe for a firm dedicated solely to sophisticated, custom designs for affluent residential properties. Walter Williams is cofounder and principal designer for Alpine Pool & Design Corp. A graduate of Western Washington University, Williams has more than 30 years’ experience in the construction industry and has partnered with William Bennett since their firm’s inception in 1987. Williams now focuses primarily on technical and aesthetic design work, serving as the clients’ongoing consultant through all project phases.

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