Ground-breaking Choices

Which type of inground swimming pool is best for you?

By Alan E. Sanderfoort

Inground swimming pools come in all shapes and sizes, but what is not so obvious is how each swimming pool is constructed. Look at a poolscape and you notice the decking, coping and tilework -- but these elements alone don't reveal whether you are gazing upon a concrete, fiberglass or vinyl-lined swimming pool. Yet, the method of construction affects overall design, cost, construction time and even how the swimming pool will be maintained.

Concrete Swimming Pools: Design Versatility

Concrete swimming pools can be fashioned into virtually any shape and size, which makes them the most popular choice for homeowners searching for a custom, high-end look or a unique solution to an atypical backyard. Regardless of the size or details of your lot, an experienced concrete swimming pool builder can create a size and shape that works with your home's architecture and surrounding landscape. The design versatility of concrete is its most outstanding benefit.

To build a concrete swimming pool, a construction crew digs a hole, installs the plumbing and lines the hole with a framework grid of steel reinforcing rods, more commonly known as "rebar." The rods are spaced about 10 inches apart and secured together with wire. A thick layer of concrete is then sprayed onto the grid and troweled to reflect the shape of the pool shell. Typically, the concrete bond beam surrounding the perimeter is 12 to 14 inches thick, while the pool floors and walls are 6 to 8 inches.

Gunite and shotcrete are the two methods for spraying concrete. Gunite uses a dry mix that is injected with water as it exits the hose. This can result in a very dry concrete, which many pool builders believe creates the most durable pool shell. Shotcrete uses a wet, premixed concrete that is pumped from a truck. Because shotcrete is a wet premix, it may contain more moisture that could impede drying time.

After curing for about a week, both gunite and shotcrete swimming pools are surfaced with a smooth finishing coat. The most popular and economical pool finish is plaster, which is actually a mixture of cement and marble sand. Other choices include pool paints, fiberglass coatings, stone aggregates (which include popular pebble-like finishes) and mosaic tiles (which can add to the cost but provide more aesthetic appeal). The entire construction process can take several weeks or more depending on the size of the pool and the materials used.

Because of the custom nature of concrete pools, it is easy to design them with special amenities, such as negative edges, elaborate water features, underwater benches, grottos and more. The only limitations are your imagination and budget.

Fiberglass Swimming Pools: Easy Maintenance

Fiberglass swimming pools are made from fiberglass-reinforced plastic, which has been molded into a specific pool shape at the factory. Therefore, what you see is what you get. Nothing during the installation phase can alter the size, depth or shape of the pool.

But thanks to the growing popularity of fiberglass swimming pools, a wider selection of sizes and shapes are now available. Most homeowners can find a model that suits their specific needs -- in an array of colors and with custom-style features found in their concrete counterparts, such as elaborate water features, beach entries and inset mosaic tile around the waterline.

The ultra-smooth surface of fiberglass is nonporous, so algae and dirt cannot penetrate the surface, which makes it easy to clean and maintain. Fiberglass does not chip, tear or alter the water chemistry, so it rarely needs refinishing and lasts approximately 15 to 25 years. Fiberglass works especially well in all climates and soil conditions because of its ability to flex and accommodate climate-caused freeze-thaw movement. Another benefit: A faster installation time, typically a week or less.

Even though they are factory-made, fiberglass pools can cost just as much, if not more than, concrete swimming pools. That's because of shipping costs to the job site, and a crane is often needed to lift the pool over the house and lower it into the backyard. As a general rule, however, an average-sized fiberglass pool costs about $24,000; prices for the same sized concrete pool start at about $30,000.

To install a fiberglass swimming pool, a construction crew digs an aptly sized hole, lays the necessary plumbing, lowers the rigid pool structure into the hole, levels it, hooks up the plumbing, and fills in around it with sand. The whole process only takes a few well-orchestrated days.

Vinyl-Lined Swimming Pools: Economy-Priced

Vinyl-lined swimming pools are best known for being the lowest cost option. Because of recent advances in engineering, these swimming pools are almost as customizable as concrete pools. Whereas there used to be just a few standard kits, it is now possible to add almost any design element, including high-end features.

A standard vinyl-lined swimming pool usually takes two to three weeks to install, less than concrete but longer than fiberglass. They also offer more flex with ground movement than concrete, an important consideration in climates with freeze-thaw cycles.

To install a vinyl-lined pool, a construction crew digs an appropriately sized hole and assembles the wall panels around the perimeter. These panels are typically made from metal or rigid plastic. Plumbing is installed and attached to the pool wall. The bottom of the hole is covered with either sand or poured concrete. A concrete bottom ensures that the base will resist erosion, footprints and other depressions, whereas a sand bottom may be prone to dimpling. The vinyl liner, which is 20 to 30 millimeters thick (about one inch), is secured to the top of the walls and air between the liner and wall is vacated with a vacuum, providing a wrinkle-free installation.

Liners come in myriad colors, designs and patterns, and some systems allow for tile to be installed around the waterline. An advantage of vinyl liners is that their extra-smooth surface eliminates the risk of swimmer skin scrapes, and like fiberglass, they also are easy to clean and less likely to harbor algae. Most vinyl liners last between 10 and 15 years before they have to be replaced due to natural wear and tear and exposure to the elements. Replacing a liner costs about $600 to $700, plus installation, and is an easy way to give a dated pool a contemporary facelift.

Photo courtesy of Gib-San Pools, Ltd.