Vinyl liner: the wall is not the waterproofing

A [...]]]> The three inground pool construction types get compared on price constantly, but price is really just a symptom of a more useful question: what's the actual structure made of, and what does that structure force you to do to maintain it over the next 20 years?

Vinyl liner: the wall is not the waterproofing

A vinyl liner pool has a structural wall — steel, aluminum, or polymer panels — that holds the shape, and a separate vinyl liner draped inside it that actually holds the water. That separation is the whole story with this type: the wall doesn't need to be watertight, only the liner does, and the liner is a wear item. Typical liner life runs 7 to 15 years depending on water chemistry consistency and UV exposure, and replacement is a scheduled, known-cost event, not a surprise repair. The upside is a genuinely smooth, algae-resistant surface with no plaster to etch or stain. The tradeoff is that a liner puncture or a bad heater/skimmer install can undermine the whole system faster than the other two types.

Fiberglass: the surface is the same material as the wall

A fiberglass pool is a single pre-manufactured shell, gelcoat surface fused to the fiberglass structure itself, trucked to the site and set into an excavated hole in one piece. Because the surface and the structure are one material, there's no separate liner to age out and no plaster to resurface — the gelcoat itself is what you're maintaining, and it's non-porous enough that these pools typically need less sanitizer and see less algae growth than plaster surfaces. The real constraint isn't lifespan, it's shipping: shell size and shape are limited to what can travel by truck, which is why fiberglass pools rarely appear in the extreme custom shapes gunite pools can achieve.

Gunite (shotcrete): rebar and sprayed concrete, then a separate finish coat

Gunite construction sprays a concrete mixture over a steel rebar frame built to whatever shape the design calls for — this is the type with no real size or shape ceiling. But the concrete shell itself isn't the finished interior surface; it gets plaster, aggregate (pebble), or tile applied afterward, and that finish coat is what's actually in contact with the water and chemicals. Plaster finishes typically need resurfacing on a 10 to 15 year cycle as they etch and roughen from chemical exposure, and the porous surface is more algae-prone between resurfacings than fiberglass or vinyl. The structural shell itself, properly built, genuinely outlasts the other two types — the maintenance burden shifts to that recurring finish-coat cycle instead.

The actual decision variable

If the shape needs to be non-standard — a custom curve, a specific depth profile, an attached spa cut into the same shell — that alone rules out fiberglass regardless of budget, because it's a shipping constraint, not a cost constraint. If minimizing chemical and cleaning time matters more than upfront cost, fiberglass and vinyl both outperform plaster gunite on that specific measure. If the pool needs to be a specific unusual shape AND needs to last decades with only surface-level maintenance, gunite is the type that accepts the shape and then asks you to budget for the resurfacing cycle instead of a liner-replacement cycle.