J.H. Cockerell Consulting Engineers

Pool Walls

The walls of large swimming pools are almost always constructed using concrete. Concrete walls can be either formed and cast in-situ, pre-cast or sprayed. Formed concrete walls offer the cheapest whole-of-life cost alternative.

Formed Concrete Walls

Concrete walls have traditionally been constructed on site between panels of vertical formwork to allow accurate positioning of steel reinforcement and placement of concrete which can be well compacted. Pools that are well designed and well constructed, with formed concrete walls, can be expected to have a useful life of approximately 50 years, requiring only minor maintenance.

Precast Concrete Walls

Factory manufactured, precast concrete walls are at first glance an attractive proposition for large swimming pools, particularly those constructed in remote locations.

Unfortunately precast concrete walls, when used to construct swimming pools, have the following limitations:-

  • Difficult to position accurately
  • Difficult to provide a long-term water-tight seal between the precast wall panels.
  • Difficult to achieve load transfer between precast wall panels.

In view of the above, precast concrete panels should not be used to construct large swimming pools. Our reports on several large pools, constructed with precast concrete walls, supports this advice.

Sprayed Concrete Walls

Sprayed concrete is concrete conveyed through a hose and pneumatically projected at high velocity onto a surface, as a construction technique.

Pools with sprayed concrete walls are typically designed with a single layer of steel reinforcement (e.g. 12mm diameter steel bars at between 200mm to 300mm centres) nominated to be positioned at the middle of a 150mm thick wall. It is very difficult to construct joints that don’t leak in sprayed concrete pools. As a result, sprayed concrete pools are often built without any joints. As sprayed pools increase in size, a lack of joints becomes more problematic (i.e. concrete shrinkage cracks open wider and the risk of cold joints in the concrete increases).

Other problems associated with sprayed concrete pool walls include the following:

  • Wall strength is limited when a single layer of steel reinforcement is located in the middle of the wall. Formed concrete pool walls typically have 2 layers of steel reinforcement, making them significantly stronger.
  • There is no way of accurately controlling the final position of steel reinforcement in the concrete wall’s cross-section.
  • The inability to reliably control concrete compaction often leads to voids in the concrete.
  • The rear of sprayed concrete pool walls usually cannot be inspected for water leaks, when the pool is filled with water to confirm it is water-tight

Conclusions regarding Sprayed Concrete Walls

Pools with sprayed concrete walls are very easy to design (e.g. typically 150mm thick concrete walls with 12mm diameter steel bar reinforcement at 200 to 300mm centres located at the centre of the wall) and are therefore popular with some engineers.

There is very limited opportunity for construction quality control of sprayed concrete pool walls. The following are either difficult or impossible to ensure:

  • wall concrete thickness
  • final location of steel reinforcement in the wall
  • incidence of concrete voids
  • whether the wall has been constructed water tight.

Sprayed concrete pool walls must be rendered before they can be tiled, introducing another material that if not correctly applied could fail.

Expect pools with sprayed concrete walls to have a useful life of significantly less than 50 years and cost significantly more to maintain than a pool constructed with formed concrete walls.