Gunite vs. Shotcrete: What’s the Difference?
Concrete pools are often referred to as “gunite” pools, but then what’s shotcrete? Are gunite, shotcrete, and concrete all the same thing? Not to worry… all will be revealed. (Doesn’t that sound ominous? I love it.)
Quick refresher: concrete is a mix of water, cement, sand, and a coarse aggregate, which is usually stone or gravel.
The cement, sand, and aggregate are the initial mixture. How the builder mixes in the water determines how we refer to it.
Technically speaking, the term shotcrete refers to either wet- or dry-mix concrete as long as it’s shot out of a hose, hence the name.
However, in the pool world, we take matters into our own hands. In this case, the matters of terminology.
For our purposes, shotcrete is the wet mix concrete. The whole cement-sand-aggregate blend is already mixed with water when it arrives at your backyard in the big ol’ cement truck.
Gunite is concrete applied with the dry-mix process, as in it’s water-free up until the builder actually applies it.
What's the difference between gunite and shotcrete for a concrete pool?
Concrete pools can be made of either shotcrete or gunite. The difference is when the concrete mixes with the water. Shotcrete refers to wet concrete that's already fully mixed before it's shot out of a hose. Gunite is dry concrete mix that only mixes with water at the nozzle when it's sprayed.
Concrete pool construction
The construction processes for gunite and shotcrete pools are similar:
- Measure and excavate the ground.
- Install the plumbing.
- Install a reinforced cage of tied steel rebar
- Spray concrete―using either the gunite or shotcrete process―encasing the rebar.
- Shape and finish the concrete pool shell.
- Let the concrete cure.
- Install Tile and Coping
- Install the patio.
- Apply the finish (plaster, aggregate, or tile).
- Start up the pool.
For gunite (dry-mix), the builders load the pre-mixed dry material into the hopper of the delivery equipment.
They use compressed air to send the material to the nozzle, where it mixes with water.
Then it sprays out at super high velocity, which compacts the material on placement.
For shotcrete (wet mix), the builders put the fully mixed wet concrete in equipment hopper and compressed air shoots the material to/through the nozzle.
Again, the material sprays out fast and compresses where applied.
Gunite: Pros and Cons
Normally if you’re pouring concrete (like a sidewalk) and you stop and later start back up, those two pours won’t bind together. They’ll be two separate pours.
So if you were to stop a rough edge and try to blend the new into the old, it’ll create a cold joint which will look different and most likely crack there.
When you’re guniting, you can stop and start again without creating that “cold joint” or plane of weakness. Because of the velocity the material is applied, it’ll still bond together.
The builders have more work time since they mix the cement on-site and can stop and start as needed.
This process tends to be less expensive than shotcrete.
The gunite process requires a super skilled operator because that person is in charge of the sand/cement/water ratio. An error there can ruin the quality of the concrete.
The dry mixture could clog the hose pipe.
Gunite produces a lot of over-spray, called rebound. It makes a huge mess. You also can’t reuse it, so it’s just wasted.
Shotcrete: Pros and Cons
While builders using shotcrete need to be skilled, they don’t have to be as technically trained as someone working with gunite because the concrete is premixed.
Shotcrete forms a strong and consistent coating.
Shotcrete requires less time.
Since shotcrete is premixed, you have to apply it quickly. You can’t stop and start because it won’t bond.
Cracks can form from shrinkage if too much water is added to the mix.
Shotcrete is more expensive than gunite.
The builders might add water to the cement mixture in the cement truck to keep it from hardening. This can compromise the strength of the concrete.
Basically it comes down to your pool builder’s preference.
It’s all concrete, just applied in different ways. Both gunite and shotcrete processes produce a good product if done right.
Concrete pools, especially when made using shotcrete process, generally cost $50,000-$100,000. By comparison, fiberglass pools cost $45,000–$85,000 upfront but have the lowest lifetime expenses of all three, which saves you money in the long run.
While the shapes and sizes are less customized, most people can find a model that fits their needs. They’re super durable and low-maintenance—not to mention pretty!
The construction process for concrete pools can take 3–6 months. The installation process for fiberglass pools is 3–6 weeks, and it’s much less messy.
At River Pools we offer fiberglass pools in Virginia and Maryland (and in other areas of the country through our dealers). Read through our ebook about the three pool types, and get in touch with us to see if fiberglass might be the right choice for you. We look forward to helping you!