Prefab, fibreglass or polyester pool: which one is right for you?

If the excavation is ready, a one-piece fibreglass pool is lowered into place by crane and the groundwork and plumbing are connected; the on-site part of the job is measured in days. In a concrete pool the same job goes through formwork, reinforcement, pouring, curing time, waterproofing and finishing, so it stretches over weeks.

The second advantage is the surface. The factory-made gelcoat surface is smooth and has no joints. A jointless surface holds less dirt and is easier to clean. There is no line item for finishing labour or grout maintenance.

The third is predictability. Because the shell is produced in a factory, thickness, geometry and strength are standard and do not depend on which crew is on site. In a concrete pool the biggest variable in quality is the team doing the work.

If a 4.80x9.60 pool fits your garden and the catalogue has 4.50x9.00 and 5.00x10.00, you lose the difference. If you want a custom shape, an L geometry, a beach entry or a freeform design, a fibreglass pool is not for you.

Transport and crane access are decisive. The one-piece shell arrives on a truck and is lowered into the garden by crane; a narrow street, a low power line, a neighbouring building or a tree can make this impossible. On narrow urban plots this is the obstacle we run into most often, and we make the call during the site survey.

Know the difference on the repair side too. Scratches and osmosis blisters in a gelcoat surface need special treatment; it is not a job every tradesman can do. In a concrete pool a cracked tile is replaced and the job is done. Take this difference into account over the long term.

They offer more freedom of size than fibreglass, because length and width can be adjusted by changing the number of panels. Time on site is shorter than for concrete. They need no crane or truck access, since the panels arrive in sizes that can be carried by hand.

The finish is a liner. A liner is economical, quick to install and comes in a choice of colours; on the other hand its lifespan is shorter than tile and mosaic, and it is replaced over the years. Plan for this as a maintenance item, not as a drawback.

A panel pool is a good balance especially on narrow urban plots and in projects with tight deadlines. For jobs that have to be ready for the season, such as hotels, the short time on site becomes the deciding factor.

Overflow systems, infinity edges, beach entries, seating ledges, integrated hot tubs and freeform geometry are all built with a concrete shell.

Depth customisation belongs here as well. Stepped floors, a separate children's section or a counter-current niche are shaped to the formwork. In a fibreglass shell, you get whatever the mould has.

On lifespan, a concrete shell with the right waterproofing and the right finish serves for decades, and it is renewed by replacing the finish. In return it is the system with the highest initial investment and the longest time on site. If you accept these two points, concrete gives you the widest freedom.

Ranked by freedom of size, from narrowest to widest: fibreglass, panel prefab, concrete. The initial investment usually follows the same order, but the choice of finish can upset the picture; the difference between a concrete pool finished in glass mosaic and one finished in ceramic tile can be larger than the difference between systems.

On maintenance, fibreglass and polyester lead with their jointless surfaces. A panel pool with a liner sits in the middle and needs periodic liner replacement. A concrete pool finished in tile or mosaic needs grout maintenance, but its finish can be repaired.

Heating and running costs are set by water volume and surface area, not by the system. In other words, a fibreglass pool and a concrete pool of the same size end up with similar electricity bills. The choice of system determines installation time and design freedom, not running costs.

If a catalogue size fits the garden, there is no need to pay more.

For a job on a narrow street where no crane can get in, but which still has to be finished quickly, a panel prefab system is the right answer. It removes the access problem and gives some flexibility in size.

A villa overlooking a view, a hotel that wants an overflow system, or a project that needs a custom geometry calls for concrete. In these three cases, jobs started with fibreglass or panels do not deliver the result wanted later on; we prefer to say so from the start.

For panel prefab pools: what are the panel material and thickness, how many mm thick is the liner, how long is the liner warranty, and how is the panel joint detail sealed?

Common to all three: pump flow rate, filter diameter, pipe diameter, the space needed for the plant room, and the scope and length of the warranty. A quote that does not state these five lines in writing is incomplete; compare them before you compare the total figure.