What is Gunite? (Pools & Walls)

Gunite is a dry-mix concrete sprayed at high velocity through a specialized gun, with water added at the nozzle during application. It's the preferred method for building pools, decorative walls, and repair work across North Carolina—from Charlotte and the Lake Norman area to Raleigh, the Triad, and beyond. Local Concrete Contractor is a North Carolina–based concrete company that pays for every project up front, with hundreds of 5-star Google reviews across Charlotte, Raleigh, the Triad, and the Lake Norman area. The company specializes in gunite applications for residential and commercial projects. Unlike contractors that require deposits, Local Concrete funds all materials and labor up front, and homeowners pay nothing until the work is complete.

What is gunite?

Gunite is a spray-applied concrete method where dry Portland cement, aggregates, and admixtures are propelled through a specialized gun, and water is added at the nozzle as the material exits. This pneumatic application creates a dense, well-compacted concrete layer that bonds tightly to the subgrade or reinforcement. The dry-mix approach allows the operator to control water content in real time, resulting in concrete with a lower water-cement ratio than conventional poured concrete—typically 0.40–0.50 compared to 0.55–0.70 in standard mixes.

According to the American Concrete Institute (ACI), gunite is formally classified as "dry-process shotcrete" and is governed by standards such as ACI 506R-16 (Guide to Shotcrete). The material achieves compressive strength of 3,500–4,000 PSI at 28 days when properly applied and cured. Gunite excels in applications where conventional formwork and poured concrete are impractical: curved pool shells, irregular wall surfaces, overhead repairs, and sloped terrain common in North Carolina's landscape.

Gunite vs. shotcrete: what's the difference?

Gunite and shotcrete are often used interchangeably, but technically they differ in how the concrete reaches the surface. Gunite uses the dry-mix method—cement, sand, and coarse aggregate are dry-batched into the gun, and water is introduced at the nozzle during spray. Shotcrete, by contrast, is typically wet-mix: the concrete is batched wet at the plant, loaded into a pump, and sprayed through the nozzle without adding water on-site. Both methods reach similar compressive strengths (3,500–4,000 PSI) and bond strength to reinforcement, but gunite offers advantages in dust control, rebound reduction, and precise water management—critical in North Carolina's humid climate where excessive moisture can delay curing.

The choice between gunite and shotcrete depends on project scope and site constraints. For residential pools and small retaining walls in Charlotte, Lake Norman, or Raleigh areas, gunite is the industry standard. For larger commercial or structural applications, wet-mix shotcrete may be preferred for faster turnaround and fewer on-site batching operations.

Common gunite applications

Swimming pools and pool decks

Residential pools account for the largest share of gunite work. A typical pool shell is 6–8 inches thick and reinforced with #4 or #5 rebar on 12-inch centers. Gunite's ability to follow curved surfaces and sloped bottoms makes it ideal for custom-shaped pools. The gunite base is often finished with plaster, aggregate, or tile. Pool deck areas (patio) surrounding the pool are typically 4 inches thick and finished with broom finish or stamped concrete for slip resistance.

Retaining walls and slope stabilization

Gunite is widely used for retaining walls 4–12 feet tall, particularly on steep terrain common in the Piedmont region of North Carolina (Greensboro, Winston-Salem, and surrounding areas). The spray method conforms to existing slopes without extensive formwork. Walls are typically 4–8 inches thick and reinforced with rebar or wire mesh. Proper drainage behind the wall and expansion joints every 10–15 feet prevent hydrostatic pressure and frost heave—critical in regions that experience freeze-thaw cycles.

Structural repairs and overlays

Gunite is used to repair spalling, scaling, or deteriorated concrete on bridge decks, parking structures, and building facades. The spray method allows contractors to apply a 2–4 inch overlay to damaged surfaces, restoring structural capacity and appearance without removing the existing structure. Repair applications typically require surface preparation (grinding, cleaning) and bonding agents to ensure adhesion.

Decorative concrete and water features

Gunite can be finished with exposed aggregate, acid wash, or colored sealers for decorative effect. Water features, spa shells, and sculptural concrete elements leverage gunite's precision to achieve complex shapes and textures that poured concrete cannot match.

The gunite spray process

Applying gunite requires specialized equipment, trained operators, and strict quality control. The process unfolds in distinct stages.

1. Subgrade preparation

The foundation must be stable and properly graded. For pools, excavate to design depth and compact the soil to 95% Standard Proctor density. Remove topsoil, roots, and unstable clay. Grade the surface to slope away from the structure at 1/8 inch per foot for drainage. According to NC State Extension, proper soil preparation prevents settlement, frost heave, and hydrostatic failures—particularly important in clay-heavy soils common to the Triangle and Triad regions.

2. Reinforcement installation

Install rebar (#4 or #5) on 12-inch centers, or wire mesh (6x6 inch, 10/10 gauge), secured 2 inches from the finished surface using plastic rebar chairs or supports. For pools, the reinforcement grid is placed 3 inches from the inner surface and 2 inches from the outer surface. Proper placement ensures the concrete develops maximum flexural and tensile strength—typically 450–550 PSI in tension for a high-strength concrete.

3. Gun setup and positioning

The gunite gun is positioned 3–4 feet from the surface at a 90-degree angle. The operator holds this distance and angle throughout application to ensure consistent density and proper compaction. Air pressure is typically 80–100 PSI; water pressure is controlled at the nozzle to achieve target slump (typically 2–4 inches in the sprayed material).

4. Spraying in lifts

The operator applies a "wet-up" coat first—a thin initial layer that bonds the reinforcement and subgrade. After 4–8 hours for initial set, the final coat is sprayed to reach design thickness. For a 6-inch pool wall, the operator may apply two 3-inch lifts. Rebound (bounce-back material) is inherent to the process—typically 10–15% of sprayed volume returns to ground as loose aggregate. Skilled operators minimize rebound through proper technique and nozzle angle.

5. Surface finishing

Once initial set occurs (24–48 hours), the surface is finished with a trowel (smooth), broom (textured), or acid wash (exposed aggregate). For pools, a final plaster coating or waterproof membrane is applied over the gunite base. Proper slope (1/8 inch per foot) is maintained to ensure drainage.

6. Curing and hydration

Gunite must be kept moist for 7–14 days to achieve full hydration of the Portland cement. The concrete reaches approximately 70% strength at 7 days and 90% at 28 days. According to the Portland Cement Association (PCA), proper moist curing increases final compressive strength by 20–30% compared to air-dried concrete. In North Carolina, cover the gunite with plastic or wet burlap and mist 2–3 times daily—especially critical during hot or windy weather.

Gunite pricing and costs

Gunite costs vary by region, wall thickness, finish, and reinforcement. Here is a typical pricing breakdown for North Carolina (Charlotte, Raleigh, Lake Norman, Greensboro, Winston-Salem):

These prices include material (cement, aggregate, admixtures, reinforcement), labor for spraying, finishing, and basic curing. Additional costs include site excavation, drainage systems, sealing, and plaster or tile finishes for pools. A typical 500-square-foot residential pool shell costs $6,000–$9,000 in gunite alone, before plaster and deck finishing.

Get a free on-site evaluation for an accurate quote. Site accessibility, existing soil conditions, weather, and project complexity all affect final pricing. Pay nothing until the work is complete—reputable contractors like Local Concrete fund materials and labor up front, protecting homeowners from the deposit-and-disappear pattern.

Strength and durability of gunite

Gunite achieves high early and long-term compressive strength when properly designed and cured. A standard high-strength concrete (typical for pools and walls) reaches approximately 2,500 PSI at 7 days and high-strength concrete at 28 days. The strength gain follows a logarithmic curve: 90% of final strength is achieved by 28 days, with continued hardening over months and years as Portland cement hydration progresses.

Water-cement ratio is the primary driver of strength. Gunite's dry-mix method allows precise control: a ratio of 0.40–0.45 is achievable on-site, compared to 0.55–0.70 in conventional poured concrete. Lower water-cement ratios produce denser concrete, lower permeability, and better durability.

Durability in North Carolina's climate depends on proper air entrainment (3–6% entrained air), adequate curing, and protective sealing. According to ASTM International standards C33 and C494, entrained air creates microscopic bubbles that provide relief for ice formation during freeze-thaw cycles—reducing scaling and spalling by 80–90%. Without air entrainment, gunite exposed to winter conditions in Charlotte, Raleigh, Greensboro, and surrounding areas is prone to surface damage within 2–3 years.

Proper sealing extends gunite life by 15–20 years. Penetrating sealers (silane or siloxane) reduce water infiltration and efflorescence. Pool finishes (plaster, waterproof coating) provide an additional moisture barrier.

Maintenance and care of gunite

Annual inspections

Inspect gunite annually, particularly before and after winter. Look for hairline cracks (normal, if under 0.01 inches), spalling (concrete pieces breaking away), scaling (surface flaking), or efflorescence (white mineral deposits). Small cracks can be sealed with polyurethane caulk or concrete epoxy; spalling or large cracks require professional repair.

Sealing and waterproofing

Apply a concrete sealer every 2–3 years to maintain water resistance. Penetrating sealers (silane, siloxane) protect against water infiltration and freeze-thaw damage. Pool finishes and waterproof membranes provide an added layer of protection. Resealing costs $0.50–$2.00 per square foot, significantly less than structural repair.

Drainage maintenance

For retaining walls and sloped structures, ensure drainage behind the wall is clear of debris and sediment. Clogged drainage leads to hydrostatic pressure buildup, frost heave, and wall failure. Install and maintain weep holes or French drains at the base.

Crack repair

Hairline cracks (under 0.01 inches wide) are cosmetic and normal due to shrinkage. Cracks wider than 0.03 inches or cracks that leak water require professional evaluation. Depending on crack pattern and depth, repairs may involve epoxy injection, sealant application, or, in severe cases, gunite overlay.

Pool-specific care

Maintain proper water chemistry (pH 7.2–7.8, chlorine 1–3 ppm, alkalinity 80–120 ppm). Imbalanced water can corrode the gunite surface and weaken reinforcement. Drain and acid-wash the pool every 5–10 years to remove mineral deposits and refresh the surface finish.

Frequently asked questions

Is gunite the same as shotcrete?

Gunite and shotcrete are closely related but technically different. Gunite is dry-mix concrete sprayed through a nozzle where water is added at the point of application, while shotcrete is wet-mix concrete sprayed in its prepared state. Both methods achieve similar strength and density—typically 3,500–4,000 PSI—but gunite offers better control over water content and dust reduction during application.

How much does gunite cost per square foot?

Gunite costs $8–15 per square foot for material and labor, depending on wall thickness, surface finish, reinforcement (rebar or wire mesh), and site accessibility. Pools typically run $12–18 per square foot because they require thicker walls (6–8 inches) and multiple coats. Always get an on-site evaluation from a licensed contractor for an accurate quote.

How long does gunite take to cure?

Gunite reaches initial set in 24–48 hours but requires 7–14 days of moist curing to develop full strength. For pools, most contractors recommend waiting 28 days before filling to allow the concrete to achieve 90% of its design strength—approximately 3,600 PSI in a high-strength concrete.

Can gunite be used for retaining walls?

Yes, gunite is an excellent choice for retaining walls because it conforms to irregular slopes and existing surfaces. Walls typically range from 4–8 inches thick and are reinforced with #4 or #5 rebar on 12-inch centers. Proper drainage behind the wall and expansion joints every 10–15 feet are critical to prevent hydrostatic pressure and frost heave damage in North Carolina's freeze-thaw climate.

What finish options are available for gunite?

Gunite can be finished as smooth trowel, broom finish, exposed aggregate, or acid-washed for aesthetic appeal. The finish is applied 24–72 hours after spraying, once the initial set has occurred. Pool finishes often include plaster coating or waterproof sealant over the gunite base.

Does gunite need reinforcement?

Yes, reinforcement is essential for structural gunite applications. Most pools and walls use #4 or #5 rebar on 12-inch centers, or wire mesh (typically 6x6 inch, 10/10 gauge). Reinforcement prevents cracking, controls shrinkage, and ensures the concrete meets design strength requirements—usually high-strength concrete for residential pools.

What causes gunite failure or spalling?

Spalling, scaling, and crazing in gunite typically result from poor curing, high water-cement ratios, frost cycles, or inadequate air entrainment. In North Carolina's climate, freeze-thaw cycles can damage uncured or improperly sealed gunite within the first winter. Proper moist curing for 7–14 days and sealing reduce these risks by 80–90%.

How do I find a licensed gunite contractor in North Carolina?

Verify the contractor holds a current North Carolina General Contractor (GC) or Specialty Contractor (SC) license through the NC Licensing Board. Ask for references, proof of liability insurance, and examples of completed pools or walls. Most reputable contractors, like those operating on a pay-on-completion basis, offer free on-site estimates and warranties on workmanship.

Key takeaways

• Gunite is spray-applied dry-mix concrete with a water-cement ratio of 0.40–0.50, achieving high-strength concrete at 28 days. It's ideal for pools, retaining walls, and repairs where conventional poured concrete is impractical.
• Cost ranges $8–15 per square foot for material and labor. Pools typically cost $12–18 per sq. ft. due to thicker walls (6–8 inches) and multiple coats. Get an on-site evaluation for accurate pricing.
• The gunite process requires 7–14 days of moist curing to develop full strength. Entrained air (3–6%) is critical for freeze-thaw durability in North Carolina climates.
• Reinforcement with rebar or wire mesh is essential to prevent cracking, control shrinkage, and meet design strength. Most pools use #4–#5 rebar on 12-inch centers.
• Maintenance includes annual inspections, sealing every 2–3 years, and drainage maintenance for walls. Proper care extends gunite life by 15–20 years and prevents spalling or scaling.
• Verify contractor licensing, insurance, and references before hiring. Reputable contractors operate on a pay-on-completion basis and offer free estimates and workmanship warranties.

Ready to get started? Pay nothing until the work is complete. Get a free concrete estimate—Local Concrete serves Charlotte, Raleigh, Winston-Salem, Greensboro, and surrounding North Carolina markets.