Comparing Concrete, Stainless Steel, and Fibreglass Pool Structures
Cloward H2O, an expert in aquatic design, has shared its insights into three different types of pool structures: concrete, stainless steel, and fibreglass.
Rob Cloward, associate principal and senior engineer at Cloward H2O, discusses the advantages and disadvantages of each of these materials and evaluates their suitability for various applications.
Concrete Pools
The most commonly used type of swimming pool construction is the cast-in-place, or poured-in-place, concrete pool. This method is well-established and has been employed to build countless pools, many of which have been in operation for decades. They are durable, can be crafted into almost any size and shape, and provide a high-quality finish.
Cloward explains: “Properly designed, reinforced, and constructed concrete pools are resistant to cracking. Commercial concrete pool structures should adhere to a minimum standard ACI 350 (American Concrete Institute) for watertight concrete, which offers guidance on concrete thickness, steel reinforcing requirements, and concrete mix specifications.”
The concrete is typically applied as shotcrete, allowing for nearly any size or shape to be created.
“Because the concrete is sprayed, the floor and walls can be constructed as a single monolithic structure,” says Cloward. “The shotcrete application method can even be used to apply concrete to high walls or ceilings. Due to the nature of shotcrete application, concrete pools will have a solid and void-free interface to the surrounding soil and other structures, adapting to in-situ site conditions.”
Concrete pools are robust and suitable for a variety of surface finishes, ranging from tile or plaster to quartz aggregate or smooth pebble. Quartz aggregate and smooth pebble finishes have become more popular recently, as they are more durable and last approximately twice as long as conventional pool plaster.
Furthermore, Cloward H2O states that cast-in-place concrete pools are generally less expensive than other pool structures. Concrete is readily available in most areas, minimising transportation costs. Skilled concrete pool installers can also be found in all regions, resulting in lower labour costs.
Stainless Steel Pools
Stainless steel pool structures offer a high-quality feel and are lighter than standard concrete pools. This makes them suitable for installation on top of buildings, such as high-rise structures or parking garages. Additionally, stainless steel pools are sturdy and corrosion-resistant, with many coming with excellent warranties.
Stainless steel pools must be installed on a poured concrete foundation or another structure. The installation process is quick, with smaller pools often delivered as a single piece, while larger pools may need to be transported in multiple sections and welded or assembled on-site.
Cloward notes: “Shipping logistics limit the size and layout of smaller pools. Pools that fit in a shipping container or on a flat truck are easier and cheaper to ship than those needing to be shipped in pieces or as oversized loads. Stainless steel pools can be shaped in various ways, but more complex designs require additional forming effort, which can increase costs.”
Clients must also consider whether salt chlorine generation will be used:
“While stainless steel is resistant to corrosion, it is not rustproof. Salt chlorine generation is not recommended for stainless steel pools, and many manufacturers will not honour the warranty if salt chlorine generators are employed.”
Stainless steel pools can be finished with bare stainless steel, a vinyl liner, or small tiles. Larger tiles are not advisable due to flexibility and thermal expansion in the pool material, which can lead to tile failure.
“Stainless steel pools are typically more expensive than concrete pools, especially for on-grade applications. However, in scenarios where the pool is built on a structure, stainless steel can offer significant cost savings due to its lighter weight and reduced structural reinforcement needs,” adds Cloward.
Fibreglass Pools
Fibreglass pools share similar advantages with stainless steel pools, such as being lightweight and easy to install. However, they are generally more affordable than stainless steel pools and possess good chemical resistance.
“Fibreglass pools are constructed around a mould, which limits their geometry to the shapes available at the manufacturer’s facility,” explains Cloward. “If a specific shape is desired, a new mould must be created, although multiple identical pools can be produced from a single mould.”
A fibreglass pool’s finish options are limited to gelcoat or small tiles. Larger tiles are not recommended due to the structure’s flexibility and thermal expansion, which may cause failure. Gelcoat finishes are susceptible to spider-web cracking, fading, and chipping, and spot repairs often do not blend well with the surrounding surface.
Cloward adds: “Fibreglass has a history of delamination as the structure ages. While resins and technology have improved, life testing of these updates still creates uncertainty.”
“Similar to stainless steel pools, fibreglass pools require a well-prepared foundation. Improper installation can lead to wall and floor deflection, cracking, and structural failure. Pools with adequate wall thickness should be considered to maintain deflection and strength within acceptable ranges.”
The size of fibreglass pools can be constrained by shipping limitations, as they are often delivered as a single, watertight structure. This type of structure can be cost-effective; however, if a custom shape is desired, a mould must be created, which increases the overall cost.
Choosing the Best Structure
“Cast-in-place concrete pools are typically the best option for on-grade pools due to their high quality, durability, cost-effectiveness, and design flexibility,” concludes Cloward.
“Stainless steel pools are excellent for installations on structures, providing a high-quality feel and significant cost savings in certain applications. Fibreglass pools, while not suitable for high-end or luxury developments, offer a cost-effective and chemically resistant option for specific uses.”
