An in-ground pool is a water-filled fixture for recreation or exercise that is permanently installed into the ground, with its top surface level with the surrounding lawn. It offers a more enduring design element within your landscape compared to an above-ground pool. When selecting an in-ground pool, you’ll typically choose from four main types of materials: various concrete mixes, fibreglass, and vinyl.
Each material type presents distinct advantages and disadvantages that you’ll want to carefully weigh before making your pool choice. Below, we’ll delve into the specifics of each in-ground pool type and the factors you should consider to determine which material is best suited for you and your garden.
Basic Types of In-Ground Pools
| Type of Pool | Key Characteristics | Advantages | Disadvantages |
| Concrete with plaster or aggregate finishes | Used for custom-shaped pools | Most durable material | Long installation time; potentially higher initial cost and maintenance |
| Concrete and tile or stone | Used as a base for decorative materials | Aesthetically pleasing; highly customisable | Difficult to repair/replace; can be costly |
| Fibreglass | Used for quick installations | Lowest maintenance; quick installation | Limitations in sizes and shapes; higher upfront cost |
| Vinyl | Used for less expensive installations | Can be any size or shape; lowest initial cost | Deteriorates over time; liner replacement costly |
01. Concrete Pools
Best for: Permanent in-ground pools requiring customisation.
Composed of steel-reinforced concrete forming a sturdy shell, concrete and plaster remain the most common in-ground pool-building materials and were the earliest to gain popularity with residential pools. The reasons for their enduring use are clear: concrete is both durable and porous, allowing the plaster-coated shell to effectively retain water, provide structural stability, and be replastered when necessary, thereby contributing to its longevity and robustness.
Despite concrete having a higher initial cost (compared to vinyl, for instance), it is often considered the most cost-effective option in the long term, as it can be maintained for many years and, with proper care, will likely never need full replacement.
Here’s how the construction works: after the ground has been excavated, the sides and bottom of the hole are lined or framed with rebar (steel rods). These can be meticulously sculpted into virtually any conceivable shape (from simple rectangles and whimsical hearts to intricate guitar designs), with the flexibility to incorporate steps, ramps, and other bespoke features.
Once the rebar framework is in place, the pool shell is created by spraying a finish using shotcrete or gunite – a combination of sand, cement, and water that is applied to the surface under high pressure via a hose. After the concrete material has cured, it is topped with plaster (a mix of cement and marble dust), which may also contain coloured quartz for enhanced aesthetics.
The plaster is what truly renders the pool waterproof and is an indispensable stage in the process. Concrete pools also serve as an excellent base for various other popular pool finishes, such as decorative tile or natural stone. This method allows a contractor significant flexibility in determining the size and shape of a concrete pool. In most cases, a pool featuring modern curves should not cost more than a similarly sized pool with a more traditional, angular shape.
Once the concrete base of the pool is established and cured (following steps similar to those above), the pool is coated with a thinset mortar, onto which tile or stone can then be meticulously set. The tile should be allowed to set for a minimum of 24 hours before being finished with a polymer-fortified grout, specifically designed to withstand constant moisture and pool chemicals.
Typically, these finishes last between 8 to 12 years. They can be challenging to repair or replace, often requiring the pool to be drained and professional intervention for even minor chips or missing tiles.
Pros:
- Most durable, gaining strength over time.
- Does not corrode or oxidise.
- Highly customisable in shape and size.
Cons:
- Longer installation time.
- Can be costly to install and maintain.
- Higher ongoing maintenance costs.
02. Fibreglass Pools
Best for: Low-maintenance in-ground pools and quick installations.
An in-ground swimming pool made of fibreglass is supplied as a large, single-piece shell. This shell arrives at your home by truck and is then carefully positioned into the pre-excavated hole with the assistance of a crane. A fibreglass pool incurs higher initial costs, but it boasts significantly lower maintenance costs over its lifespan. It does have limitations in terms of size and is available only in pre-fabricated moulds.
Unlike concrete pools, fibreglass pools are ready-made, which limits the ability to request a fully customised design. However, most fibreglass manufacturers offer a wide array of models and sizes to choose from, and features like steps, integrated spas, and benches are typically pre-formed as part of the shell.
Fibreglass considerably simplifies and accelerates the pool-building process. Its smooth interior surface is slick, making it difficult for algae to adhere. After 10 to 15 years of exposure to sunlight and chemicals, the fibreglass gel coating may begin to show signs of deterioration. Recoating the gel is not a straightforward process because the new coating does not easily bond with the older one, making it a tedious procedure.
However, a fibreglass pool is inherently less prone to algae growth, and over a 10-year period, the lifetime maintenance costs for this type of pool are the lowest. It should rarely require acid washing or extensive deep refinishing (apart from the potential need for topical recoating) unless it has been exposed and in a very sunny environment for an extended duration.
Pros:
- Low-maintenance requirements.
- No deep surface refinishing typically necessary.
- Not prone to algae growth.
Cons:
- Limited shapes and sizes due to pre-fabricated moulds.
- Fibreglass gelcoat can deteriorate over time.
- Slick surface; recoating can be difficult.
03. Vinyl Pools
Best for: The least expensive in-ground pools.
Pools that are lined with vinyl are constructed with metal or plastic frames either above or below ground, or they are set directly into the excavated hole. Prefabricated supporting walls or panels made of plastic, steel, or aluminium are joined to the frame, creating a form that is then lined with heavy vinyl to create the pool shell.
The bottom of a vinyl liner rests on a bed of sand or other material, while the top is secured by the coping, which provides a finished edge and also serves as a border for the pool deck. Vinyl liner pools are typically the least expensive in-ground swimming pools and offer the flexibility of being built in virtually any size and shape.
Like other pool finishes, vinyl deteriorates over time due to exposure to the elements and pool chemicals. Some liners are equipped with fungus and UV inhibitors, which can extend the life of a vinyl liner from an average of 10 years to approximately 18 years. Depending on your location, a vinyl pool can be the most economical option, with costs typically ranging from approximately £18,000 to £45,000.
Pros:
- Least expensive type of installation.
- Available in any size/shape.
- Can opt for fungus/UV inhibitors to extend lifespan.
Cons:
- Vinyl deteriorates over time.
- Liner replacement is a costly process.
- Water chemicals need precise balancing to slow down deterioration.
04. Gunite Pools
Best for: Custom-shaped, durable pools, similar to concrete.
A gunite pool is very similar to a concrete or shotcrete pool, with one key distinction. While shotcrete is a wet mix, pre-mixed and then sprayed onto a steel reinforcing structure, gunite is applied dry, with a water source introduced at the nozzle to hydrate the mix just before application. This makes gunite a dry mix process, whereas shotcrete is a wet mix.
To construct a gunite pool, the process mirrors that of a concrete pool. First, a hole must be excavated, and then steel reinforcement is meticulously placed along the walls. When it’s time for the gunite application, the dry mix is loaded into a hopper, which then pumps the still-dry gunite mixture through a hose to a nozzleman.
The nozzleman, positioned at the end of the hose, performs several crucial tasks. They control the precise amount of water introduced to the mix as it is sprayed onto the reinforcing steel. Simultaneously, they are responsible for aiming the nozzle to create a uniformly filled and sculpted surface. After application, the gunite is allowed to cure for approximately 28 days, at which point it is ready for any chosen finish.
Choosing an In-Ground Pool
Building an in-ground pool is a significant decision. Many factors are paramount when selecting the type of in-ground pool you should install. Before opting for any specific pool type, research as many images of pools as you can to gain a clearer understanding of the designs that appeal most to you. If you are particularly drawn to a specific size or shape, this preference may dictate the specific material type required for your pool.
Are you planning to reside in your house for the long term? If so, you might prefer one of the more durable material options for your in-ground pool. Pool maintenance, truly, involves an ongoing list of tasks. Will you engage a professional pool maintenance company, or do you intend to perform your own maintenance? The level of maintenance you are willing to undertake will most certainly be a strong indicator of which material type you should choose.
Finishes
We’ve highlighted some key factors to consider when selecting a pool finish:
- Durability: If your pool is situated in a location that experiences annual freezing temperatures, you will want a more durable finish capable of withstanding the cold.
- Costs: Larger pools will naturally cost more than smaller pools, and the same applies to your choice of tile. Painted or vinyl pools typically offer the cheapest types of finishes, while plaster and tile tend to be on the more expensive side.
- Maintenance: Fixing any broken or damaged tile is a time-consuming and costly process that often involves partially draining your pool. Conversely, vinyl can be repaired underwater in a matter of seconds using a small repair kit.