Concrete Pool Construction: How Does Shotcrete Work?

EXPERT INSIGHT BY BILL DRAKELEY

Strength in Concrete

The importance of custom construction and style in your concrete pool


As someone who worked his way up from servicing the concrete pool at my parents’ swim club to building and designing pools for the family business, I learned the importance of both education and hands-on experience in this industry. I appreciated the beauty of a custom-built pool once it was completed and saw how important proper construction techniques were to achieving that end result. I began to ask questions about installation practices and, over the years, acquired the skills necessary to build concrete pools—via the shotcrete process—that are not only incredibly durable, but which also have a tremendous amount of design flexibility. These are two key points that attract many high-end pool buyers to choose concrete, and it’s important to understand how the pool’s beauty and integrity is obtained through shotcrete installation.

 

Inspired by classic Hollywood, this client requested a “Betty Davis pool.” After building the rectangular pool, we added faux expansion joints to capture the look of a pool you’d see in the 1920s.

 

Understanding the Shotcrete Process

First off, what is shotcrete? Shotcrete is a process in which mortar or concrete is sprayed at a high velocity to reach a certain compaction or density level. The concrete is applied through either a wet-mix or dry-mix process. I use wet-mix cement (the process most people are referring to when using the term “shotcrete”), while other builders use dry-mix (sometimes called “gunite,” though both processes are technically shotcrete). Either process will give you an incredibly strong pool, as long as the installer uses proper application techniques.

To make sure your pool is structurally viable, you want to find a builder who has tested his placed concrete for proper strength gain. We follow guidelines outlined by the American Concrete Institute (ACI) and the American Shotcrete Association, which both suggest that wet-shot concrete should be water-tight and between 4,000 and 8,000 psi. Our company will receive verifiable test results on strengths. One of the advantages of the process is that the concrete gets stronger over time. This means your pool should not crack or leak and should remain water-tight as it ages.

Your builder must be able to make a clear assessment of your property and the desired pool location. The builder should run soil tests to ensure your soil is weight-bearing. One of our clients wanted a pool right off his deck, but during house construction, the contractor had created a plateau in the backyard using the excavated soil. This material was not suitable for supporting the weight of a pool so we had to remove all of it and bring in an engineered soil with structural retaining walls. This added to the cost of the project, but it was necessary in order to create a sound weight-bearing base. The result was exactly what the homeowner wanted: a round perimeter-overflow spa and a pool with two vanishing edges in the best location for the property.

Builders must also be aware of the ground’s behavior throughout seasonal changes. Fortunately, concrete pools installed via shotcrete are incredibly strong, making them suitable for any region because they can withstand all types of weather.

All aspects of the shotcrete process have a bearing on the success of the installation. Soil, forms, steel, plumbing, concrete, and its chemistry need to be applied correctly. Before the pool can be filled with water, the concrete must be cured, a process that keeps the concrete shell cool and wet to maintain its density and ensure it meets the required psi strength stipulations. This takes up to 28 days and is achieved through soaker hoses that spray the pool walls and continuously recycle the water. Reputable high-end builders are experienced in all of these critical processes, giving you the peace of mind that your pool is built to last.

Customizing Your Pool Shape

Besides structural viability and water tightness, the other major benefit of shotcrete technology is that you have no design limitations; you can have any size, shape, and parameters you want. In fact, your only limitations are budget and boundary restrictions. Elevations and topography issues can work in one’s favor with shotcrete technology.

In terms of architecture and contours of the property, certain backyards are more suited to certain types of pools. Flat, linear backyards are often ideal for an English garden rectangular pool. A hillside woodsy area is suitable to a freeform pool with minimal stone and natural foliage around it. If the site is conducive to a spectacular vanishing edge, then we’ll suggest it; but we won’t push for one unless it fits.

Clients typically come to us by word of mouth and with something already in mind, such as a pool they admired while on vacation or a photo out of a magazine. Our discussion with them will then generate a few different concepts, taking into consideration the house, elevations, and water-in-transit, as well as the pool’s intended use—social affairs, recreation, lap swimming, or a combination.

We do all of our design presentations by hand. Because planned views only give you a bird’s eye view, which is never the way you’ll actually be looking at your pool, we always do measured perspective drawings. These drawings show the pool as you’d be looking across it, giving you a sense of reality and allowing you to see what your view will be when relaxing poolside or looking out your kitchen window.

Some clients know exactly what they want, like one of our past clients who requested a “Betty Davis pool.” She showed me a picture of a 20-by-40-foot pool that was cast in place with invisible straight lines in the concrete across the bottom and where the floor met the walls—this was a classic Hollywood pool. At the time, this look was achieved with expansion joints; shotcrete applications are monolithic and don’t use expansion joints. After shooting full thickness, we troweled in faux expansion joints to recreate that style; the end result truly looks like a pool from the 1920s!

Most clients are open to suggestions. My goal is always to discuss all of their ideas and create an environment that fits their home’s architecture, their taste, and their lifestyle. Our advice to a homeowner who is deciding on a pool builder is to find one who is an expert on relevant construction and who establishes open lines of communication. He or she should have the ability to translate your ideas into a perfectly executed design and final product.

 


is a third-generation pool builder/designer and president of Drakeley Swimming Pool Company in Bethlehem, Conn. Bill is a platinum member of the Genesis 3, known for its ongoing education in the pool industry. He is also a certified shotcrete examiner through the American Concrete Institute.

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