How concrete (gunite/shotcrete) pools are built with style to impress and durability to last
—Updated October 16, 2024
When researching information on backyard swimming pools, you will often see the term “gunite pool.”
What is gunite anyway? Is it different from concrete?
And what’s the deal with shotcrete—is that the same as gunite or something else?
For decades, gunite has held a vaunted place in swimming pool construction. Because the material provides unparalleled levels of design flexibility and lasting stability, it remains the preferred choice for inground pools across the country.
Gunite is a concrete blend of three chief ingredients: sand, cement, and water.
It’s applied through a high-pressure hose. Once the material cures (dries and hardens), it becomes rock solid, forming a thick, enduring structure.
Let’s take a look at some basics about this material, how it’s used in pool construction, its relationship to shotcrete, and the benefits that both gunite and shotcrete deliver.
Gunite and shotcrete are forms of pneumatically applied concrete, meaning they are sprayed on with a high-pressure air hose.
After determining the inground pool’s design and engineering, typical gunite construction begins with layout and excavation processes.
Pool contractors always pair gunite with another strong building material—steel. So, after the hole is dug for a pool, crews install a network of steel bars, known as rebar.
According to a steel “schedule,” crews lay the rebar in the hole at specific intervals.
These metal rods form a cage-like network throughout the entire stretch of the future pool, including a gunite spa if the project includes one.
Set on concrete blocks called dobies, the metal network is suspended several inches in the air so the rebar does not touch the soil beneath it.
This way, plenty of space remains all around and under the steel bars to be filled in by the fresh gunite.
In the excavated pool hole, crews strategically lay a network of steel bars to reinforce the gunite or shotcrete. They bend the bars to shape features such as steps, benches, and tanning ledges.
With the steel skeleton in place, the pool is ready for plumbing and electric. Once these two phases are complete, it’s time to shoot in the gunite.
Using a special, heavy-duty hose, crews spray the concrete blend at high velocity onto the steel grid. They apply thick layers of the material across the entire pool, creating a dense floor and walls.
Pool crews shoot gunite or shotcrete through a high-pressure hose, applying a thick layer of material that fully envelopes the steel bars that form the pool’s backbone.
Now, it’s a waiting period for the gunite shell to cure (dry and harden).
Depending on outdoor temperatures, wind, and humidity, the main “initial” phase of curing takes 7 to 10 days. During this period, water is sprayed onto the gunite at least twice a day (depending on weather).
Watering slows the speed at which the gunite’s surface dries. By preventing the surface from drying much faster than the interior, the shell achieves a better, more uniform cure that produces maximum hardness.
It’s worth mentioning that the curing process is ongoing. It takes about one month to complete the majority of the curing; during this period, the gunite will achieve about 70% to 80% of its overall strength. It will continue curing for years—and actually forever.)
After the initial, 7-to-10-day “water” curing is complete, the shell is hard enough for the next phase of construction: Plaster.
Plastering crews apply a gleaming coat of marcite, ColorQuartz®, or pebble finish over the interior of the gunite pool shell.
A plastering crew arrives to apply the interior coat of finish on the gunite shell. This final coating is what actually waterproofs a gunite pool.
(Technically, plaster refers to plain marcite, a blend of cement and marble dust. But commonly, the term “plaster” is used not only in reference to marcite, but also to the process of applying the interior finish—regardless of the material.)
Increasingly, pool builders choose ColorQuartz® or pebble for the interior finish instead of plain marcite.
These two upgrade finish options endure years longer than marcite, and both will enhance the appearance of any gunite pool’s interior.
Other critical elements go into gunite construction, including pool tile, plumbing, electric, and perimeter coping, and decking.
Colorful pool tiles are used to trim the waterline of a gunite pool as well as other feature such raised bond beam. Multiple options for perimeter coping are available to create a kind of “picture frame” around the pool’s silhouette.
However, what truly sets gunite design and construction apart from—and high above—prefab fiberglass vessels and vinyl pools are the gunite, steel, and interior finish.
And what puts the completed gunite project way ahead of the other two inground varieties are its incredible durability and gorgeous design options that this material triifecta makes possible.
You can pick the pool shape, size, and depth, you like for the configuration that’s best for your family and for your backyard space.
For a design, you can tailor your project as a classic Greek-Roman, a curvy free-form, and contemporary geometric, or simple or modified rectangle.
And you can make any of these choices into an infinity-edge pool or seamlessly integrate a custom spa.
Take a “standard” pool shape, such as a Roman, and customize the gunite configuration and integrate various features such as a tanning ledge in any size or shape.
An array of other design features are possible, such as a tanning ledge, bubbler fountains, grotto waterfall, swim-up bar or swim-up table.
Contractors routinely configure gunite pools to integrate raised bond beam, retaining walls, and planters and landscape pockets.
You can also construct a gunite pool on a sloped yard with multi-level pool deck or even a design that’s built high off the ground.
What’s essential to understand here is that both gunite and shotcrete are blends of concrete.
Between the two, the term gunite is more widely used in reference to swimming pools. However, what most people don’t realize is that shotcrete is actually a type of gunite.
Shotcrete is actually the generic term for any type of sprayed concrete or mortar. What we consider shotcrete, as it relates to pools, began emerging in the late Seventies.
The primary variations between the two blends are the preparation and one chief ingredient.
Whereas both gunite and shotcrete contain a gravel (aggregate) of sorts; the gravel in shotcrete is slightly larger than in gunite. Gravel for shotcrete is also screened for consistency.
However, for our purposes, the main difference is the point at which the water is introduced. Gunite is a dry mix; shotcrete is a wet mix. Let’s look at these differences in more detail.
Both gunite and shotcrete produce rock-hard shells that withstand pressure from shifting soil and the weight of thousands of gallons of swimming pool water.
First, it’s key to understand the preparation of gunite and its application during construction. It begins with a truck or gunite rig bringing dry loads of material to a job site.
There, the dry materials go into a container called a hopper. The hopper blends the ingredients, creating the gunite mix.
The hopper feeds the still-dry mix into a high-pressure hose. The hose has a nozzle and is operated by a professional known as a nozzleman.
Using an additional separate line and tip that connects to the gunite hose, the nozzleman adds water to the dry mix as it exits the hose.
Now the blended gunite mixture is wet and is sprayed over the awaiting steel rebar network to form the tough structure of a new pool.
On the other hand, the blending process for shotcrete begins before the material ever reaches the pool site.
Composed primarily of sand, cement, and pea-sized gravel, the dry blend is prepared at a typical ready-mix concrete facility, commonly called a “batch plant.”
These dry materials go into a large concrete rig with a big, rotating barrel. (You have probably seen these rather imposing-looking vehicles on the road before.)
Along with the shotcrete mix, the barrel also contains water. The rotating barrel mixes the dry ingredients with the water to produce a smooth blend of material.
This wet shotcrete will be ready for use as soon as the truck arrives at the job site.
As with gunite, a high-pressure hose is used to spray the material into the pool hole and steel network to create a solid structure.
Unlike gunite though, the air is added to the already wet mix at the nozzle. (In the case of gunite, air is what moves the dry material through the hose.)
Shotcrete uses a specialized pump to move the wet material through the hose, and a separate air hose supplies the air pressure required for application.
When it comes to transporting and applying the material to build a pool, gunite and shotcrete differ slightly from each other.
But when it comes to the final product, the two are extremely comparable.
The bottom line: Don’t get caught up in the distinctions between the two. Again, both are concrete, and both will create long-lasting pool shells that look great and go the distance.
Around the country, reputable pool builders construct inground pools using either. Depending on where you live, you will find gunite pools, shotcrete pools, or both.
Due to various local factors, pool contractors may use one material over another. In some regions of the U.S., gunite is dominant; in others, shotcrete is more prevalent. Or, the use of each might be about evenly split.
Both gunite and shotcrete are highly adaptable to a pool’s form, producing flowing lines, various depths and contours, and intricate shapes and features.
Either way, it’s all good. What matters most, is both gunite and shotcrete are ideal for inground swimming pool construction.
Both create solid, monolithic structures with superior durability and flexibility for any backyard design.
Both produce visually appealing pools and spas in any size, shape, style, or configuration.
Both make it possible to include a range of exciting, attractive, and functional design features.
And any day of the week, both beat vinyl liner or fiberglass for ensuring a lasting, versatile, feature-packed aquatic resort that makes any backyard look better.
Note: Because the term gunite is so widely used in reference to pools, from here on, this article will simply use “gunite” when describing pools built from either gunite or shotcrete.
Since gunite is so flexible for design and durable for longevity, it has for decades reigned supreme as the standard for both commercial and residential pool construction.
Several million gunite pools across the country provide fun, fitness, relaxation, and style in residential backyards.
Thousands more provide the same at motels, hotels, schools, universities, athletic facilities, public aquatic centers, apartment complexes, and community home developments.
By building with gunite, various decorative and functional features—from infinity edges to sunken fire pits—come together in a stunning, cohesive creation.
For a beautiful, enduring aquatic upgrade, homeowners almost always would prefer a pool built with gunite over vinyl or fiberglass.
Fiberglass and vinyl liner pools may allow for quicker installation. Vinyl liner pools and some fiberglass units sell at a lower initial cost.
In any event, when it comes to the finished product, both fall way short of their gunite counterpart. Just about any time you see a jaw-dropping photo of a swimming pool, you can bet it’s a gunite project
With gunite, options for pool design, size, and shape cross the spectrum. Whether building pools with smooth curves, sharp angles, or both, the material delivers on all fronts.
From beach entry pools to elevated rimflow spas, a myriad of sophisticated decorative and functional features can be added to boost your gunite pool’s overall style and beauty.
You can have a private aquatic resort in virtually any size, shape, depth, and configuration that works best for your budget, backyard, lifestyle, and aesthetic preferences.
Along with distinctive style and ultimate design flexibility, there’s another reason that gunite is so widely used for pool construction.
Gunite provides an enduring creation: a stable, steel-reinforced concrete structure that holds water and stands the test of time.
With gunite and shotcrete, the pool structure can even be built partially or entirely above the ground to take advantage of a sloping yard—and deliver stunning results!
You find gunite pools in all kinds of climates, soils, and elevations. Its proven track record as the go-to-choice for swimming pools spans decades and all parts of the country (and globe).
The key to its performance lies in its tensile strength—its ability to endure external force until it is compromised.
Along with boasting extremely high tensile fortitude, gunite brings something else to the table: flexibility. That’s right, being flexible makes gunite perform even better for swimming pool durability
The reason comes down to dirt—that is, shifting ground. It’s true: Never entirely static, soil under and around a pool moves in place.
Soil continually contracts and expands from factors such as compaction, water intrusion, freezing and thawing, and dry conditions such as drought.
In addition, soil changes occur from earthquakes—even tiny ones we often do not realize even occurred.
The lesson here is that a pool shell needs to “give” and be able to “go with the flow” of soil changes.
The structure—as tough and solid as it is—must display a dual personality so it can move and expand—and do it all without cracking!
It’s this twin set of attributes that makes gunite a performance superstar.
The gunite shell can handle the pressure that almost any backyard can dish out. After all, it’s not a coincidence that in California—earthquake country—hundreds of thousands of backyard pools are gunite.
The same goes for commercial pools. There’s a reason you virtually never see any type of pool other than gunite at a hotel, school, YMCA, or community center.
Businesses that own and maintain these kinds of facilities know what works best and provides the most overall value.
They require facilities that can be used by scores of guests and still hold up their appearance, safety, and durability. For decades, they have been able to count on gunite pools to meet these needs.
Gunite provides the freedom to accommodate various space constraints and site conditions. With their superb resilience and all-around good looks, these pools deliver tremendous value.
Gunite pool builders can develop bold, sophisticated designs that can overcome challenging site conditions and accommodate for bi-level topography,
Now that you understand more about the basics of gunite and shotcrete construction, size, shape and design versatility, and how both ensure a lasting upgrade for your home, it might be time to consider adding one to your backyard.
To learn more about gunite pools and how you can get started on one, contact your local Blue Haven Pools office; you can view a national office directory here.