Comprehensive Guide to In‑Ground and Above‑Ground Swimming Pool Design & Construction

Background

Concrete is the dominant choice for in‑ground manufactured pools, accounting for roughly 60% of installations today. Its unparalleled flexibility allows designers to create virtually any shape, size, or spa configuration, while a steel‑reinforced excavation ensures long‑term stability. Fiberglass pools, representing about 7% of the market, are factory‑made shells that arrive on site and are set into a pre‑excavated hole; their options are more limited in shape but they offer faster installation and lower maintenance. Vinyl‑lined pools, the third major category at 33%, are constructed on‑site by installing a custom‑fit liner after decking and filling. Historically restricted to geometric shapes, modern vinyl liners now support free‑form designs as well.

Above‑ground pools continue to evolve, with manufacturers striving to reduce fabrication costs while maintaining structural integrity. Innovative designs now allow for flexible sizing and configuration, simplifying assembly without compromising durability.

Typical above‑ground pools feature a machined sheet‑metal exterior forming a continuous circle or oval. Reinforcing posts—mounted around the perimeter—provide support and maintain wall alignment. These posts are assembled with upper and lower rails, plate connectors, and caps to secure the structure.

All above‑ground pools consist of a sidewall, a water‑impermeable liner, and a supporting frame. The frame typically includes a lower rail and a top rail to which the sidewall attaches, while the liner is affixed along the upper inner edge.

History

Swimming as a formal activity dates back to 2500 B.C. in ancient Egypt, while the Romans pioneered the first purpose‑built pools in the first century B.C. These early bathhouses, often heated with spring water, were architectural marvels reserved for the elite, yet most people still swam in natural bodies of water. The concept of a dedicated pool continued to evolve, with the first European swimming club founded in 1837 in London. The modern Olympic Games of 1896 spurred a dramatic increase in public interest and pool construction worldwide.

Raw Materials

Manufacturing pools requires a mix of durable materials: polyvinyl chloride (PVC) plastic, galvanized steel or other metals, fiberglass composites, concrete, and polyurethane foam. Concrete pools use reinforcing steel bars ranging from 0.38 in (0.97 cm) to 0.75 in (1.9 cm) in diameter, tailored to structural needs. All plumbing pipes must be at least schedule 40 PVC and stamped with ASTM approval. Liners are typically high‑density plastics engineered for long‑term water contact.

Design

Pool design reflects the unique spatial and budgetary requirements of each client. Concrete offers the greatest design freedom, allowing any shape or configuration. Vinyl‑lined pools are moving beyond geometric constraints, embracing free‑form aesthetics, while fiberglass pools remain one‑piece factory units with limited shape options. Design drawings specify exact shape, elevation, and size, and engineers perform soil and structural analyses to optimize placement and ensure structural soundness.

Pre‑installation soil analysis guarantees a stable foundation. Water circulation systems—drawn from the pool’s bottom to the surface—are essential for maintaining water quality. All electrical wiring must be grounded, and breaker protection is required for underwater lighting to meet safety standards.

The Manufacturing Process

Below is a step‑by‑step overview of constructing a vinyl‑lined concrete pool.

1. Finalize design drawings and obtain a grade‑level assessment. Excavate the site accordingly.
2. Mark the pool perimeter with stakes: initial 2 × 3 in (5.1 × 7.6 cm) stakes for the exact dimensions, followed by a secondary set outlining a 6 ft (1.8 m) larger boundary to allow working space.
3. Use a bulldozer to level the excavation, ensuring a 2‑in (5.1 cm) allowance for bottom material. Smooth the bottom with sand, vermiculite, cement, grout, or stone dust to provide a stable surface for the liner. Calculate pipe sizing based on total water volume.
4. Install the continuous fiberglass wall panels, beginning with corner sections. Each panel features machined holes for lights and skimmers and is secured with steel rods driven through the bottom holes.
5. Attach the main drain: connect it to the pump’s suction side, install two 1.5‑in (3.8 cm) plugs into the drain’s threads, and seal with duct tape to prevent debris ingress.
6. Excavate below the existing grade and below the wall to accommodate the drain. Set a concrete square beneath the drain to lock it in place.
7. Verify wall alignment and levelness, then pour a concrete collar around the pool’s perimeter (6 in or 15.2 cm deep) to secure the walls. Allow 24 hours for curing before finishing the bottom.
8. Pour the concrete bottom using either truck‑pumped concrete or gunite, the latter delivering dry cement and sand through a hose with water added at the nozzle.
9. Apply vermiculite‑cement or grout for a durable bottom. Install plumbing—black poly (coil pipe) or PVC schedule 40—along the top of the collar.
10. Run plumbing from each fitting (skimmer, main drain, return) to the filter. Apply pipe compound or non‑hardening Permatex on the threads.
11. Secure fittings with two pipe clamps and allow 15 minutes for the clamps to set.
12. After vacuum cleaning, fill the pool. If large rocks are used for backfill, cover pipes with sand to avoid damage.
13. Activate all equipment: add chlorine, muriatic acid, and stabilizer. Run the filter continuously for the first 24 hours to achieve 99% clarity, then maintain 6 hours of operation daily.
14. Maintain water temperature between 80.6–86 °F (27–30 °C). Excessive heat can crack the structure or compromise the vinyl liner’s elasticity.
15. Keep suction pipe velocity below 5 ft (1.52 m)/s and pressure pipe velocity below 9 ft (2.74 m)/s. A slower filtration rate improves contaminant removal.

Quality Control

During construction, we conduct rigorous checks: ditches and piping are capped and pressurized to detect leaks; electrical systems are inspected by certified code examiners; gunite and concrete surfaces are evaluated for smoothness and integrity; and reinforcing steel is inspected for stress or defects.

Byproducts & Waste

Construction generates significant recyclable materials. Galvanized steel reinforcement is melted and remanufactured; concrete cuttings are disposed of responsibly; and liner plastic waste is recycled whenever possible. Backwashed water is returned to the municipal system, and all excess materials are handled to minimize environmental impact.

The Future

Ongoing innovations are reshaping pool construction: lighter‑weight above‑ground designs simplify assembly; advanced laminates made from woven polypropylene mesh resist bursting while preventing leaks; fiber‑optic lighting offers safer underwater illumination; and automated pool systems enable homeowners to program maintenance tasks.

Where to Learn More

Other

Above Ground Pools Web Page. December 2001. https://www.above-ground-pools.com.

Pleasure Pools Web Page. December 2001. https://www.pleasurepoolinc.com.

SwimCSI Web Page. December 2001. https://www.swimcsi.com.

The Swimming Pool Buyer’s Guide Web Page. December 2001. https://www.swimmingpoolbuyersguide.com.

Bonny P. McClain