Fiberglass vs. Concrete Pools: Does the Digging Process Change?

When you decide to add a swimming pool to your property, the first major decision is usually the material: Concrete (Gunite/Shotcrete) or Fiberglass?

Most homeowners make this choice based on surface texture, maintenance needs, or installation speed. However, few realize that the construction journey—specifically the swimming pool excavation—looks very different depending on which option you choose.

While both start with a heavy machine arriving to start digging for a pool, the methodology, precision, and size of the hole vary significantly. As a professional pool excavation company, we approach these two projects with different mindsets.

In this guide, we will break down the technical differences between digging for concrete versus fiberglass, and how these differences impact the timeline and the cost of pool excavation.

1. The Shape and Size: "The Over-Dig"

The most visible difference when digging for pool installations is the size of the hole relative to the water's edge.

Concrete Pools: The "Cage" Approach

When we perform excavation for swimming pool projects using concrete, we are essentially digging a hole to build a structure inside of.

• The Over-Dig: We typically dig the hole 2 to 3 feet wider than the finished pool dimensions.
• Why? Concrete pools require a complex cage of steel rebar to be tied around the perimeter. Plumbers and electricians also need space to walk around the outside of the steel shell to run pipes and conduits.
• The Structure: In many cases, the earth acts as the outer formwork for the concrete. The hole is rougher, and the precise shape is defined later by the steel and the sprayed concrete (gunite).

Fiberglass Pools: The "Glove" Approach

When digging a pool for a fiberglass shell, we are creating a cavity for a pre-manufactured object to sit in.

• The Tight Fit: The excavation is much tighter. We usually only over-dig by about 6 to 12 inches.
• Why? The shell is rigid. We don't need room for workers to stand outside it. In fact, too much space is bad because it requires more backfill material to support the walls.
• The Template: The shape must be dug exactly to the manufacturer’s specifications. If the fiberglass shell has steps on the right side, we must dig in swimming pool steps on the right side of the earth to match.

2. Precision and Leveling

While all swimming pool excavators near me aim for accuracy, the margin for error changes between the two types.

Concrete: Forgiving

Concrete is a liquid stone. If the pool excavation near me is slightly too deep or a bit crooked, the concrete sprayers can adjust the thickness of the gunite to correct it. The excavation is a "rough draft"; the steel and concrete create the "final draft."

Fiberglass: Unforgiving

Fiberglass is the opposite. The shell is delivered on a truck and cannot be bent or altered.

• The Floor: The bottom of the hole must be perfectly level. If the floor is off by even half an inch, the water level in the finished pool will look crooked (e.g., the water will touch the tile line on one side but be two inches lower on the other).
• The Base: We don't just place the shell on dirt. We must dig deeper to accommodate a 4-to-6-inch layer of clean crushed gravel or chipped stone. This gravel bed must be laser-leveled before the crane lowers the pool.

3. Backfilling and Soil Removal

The question of "where does the dirt go" (Muck Away) affects the cost of pool excavation, and this volume differs between the two.

• Concrete: Because of the large over-dig (working room), we remove more soil from the ground. However, once the concrete is shot and the plumbing is done, we often use some of that native soil to backfill the trench around the pool.
• Fiberglass: We remove less soil initially (tighter hole). However, we generally cannot put the native soil back. Fiberglass pools require "clean" backfill (gravel or sand) that won't settle or expand against the flexible walls. This means we are hauling away dirt and trucking in tons of stone, which changes the logistics for the pool excavation company.

4. Stability and Groundwater

If you live in an area with a high water table, the excavation strategy shifts.

• Concrete: A concrete pool is incredibly heavy. It is like a boat made of stone; it is unlikely to float. While we need to keep the hole dry during construction, once the concrete sets, the weight keeps it in place.
• Fiberglass: A fiberglass shell is light. If we dig in swimming pool depths and hit water, there is a risk. If groundwater builds up under the shell, the pressure can actually lift the pool out of the ground or bulge the floors.
  • The Fix: When digging for fiberglass in wet areas, we must install a "dewatering system" or a hydrostatic valve permanently under the pool to relieve pressure. This requires deeper, more specific excavation work (sump pits) than a standard concrete dig.

5. Cost Implications

Does the pool type affect the pool excavation cost? Yes.

Generally, the act of swimming pool excavation for a concrete pool is more expensive in terms of pure digging volume. The hole is bigger, taking more time and more trucks to remove the spoil.

However, the preparation of the hole for fiberglass can balance that cost. The laser-leveling of the gravel base and the purchase of tons of bedding stone add to the expense.

When you ask for a quote, ensure you specify the pool type. If you tell a contractor you want to dig a swimming pond or concrete pool, and then switch to fiberglass, the quote will need to be completely recalculated.

Conclusion

Whether you choose the durability of concrete or the speed of fiberglass, the project starts in the dirt.

• Concrete excavation is about volume and creating a workspace.
• Fiberglass excavation is about precision and creating a perfect mold.

Understanding these differences helps you appreciate why swimming pool excavators near me might ask so many technical questions before giving you a price. The dig sets the foundation for everything that follows.

Need a Digging Expert?

Are you planning a project and searching for "pool excavation near me"? Whether you are pouring concrete or dropping in a shell, we have the machinery and the expertise to dig the perfect hole. Contact us today to discuss your soil conditions and get an accurate estimate for your pool excavation cost.

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