Pool Wall Structure Options

I. Introduction

Many outdoor swimming pools suffer badly from subsidence of the paving around the pool because it is laid on the fill material that is loosely tipped around the pool walls after they have been built.

The best system consists of:

• "Polyblok" reinforced concrete ICF (Insulated Concrete Forms) pool walls on a substantial concrete footing.
• Structural concrete pool terracing slabs that are connected to the ICF pool walls with reinforcement and prop the top of the pool wall and provide a rigid foundation for the pool paving around the swimming pool.
• All Bluepools designs incorporte this simple but very important principle.

The history of swimming pool construction can be divided into two distinct eras: Before PVC Liners and Post PVC Liners.

II. Before PVC Liners

Before PVC Liners there were only two ways that professional pool builders used to construct concrete swimming pools:

• By constructing a very heavy thick high reinforced concrete tank using conventional concrete that complied with BS 8007.
• By constructing a quite thin reinforced concrete tank using very high strength "Gunnite" concrete that is sprayed onto timber "formwork" (plywood on a framework of heavier timber to support the wet concrete and form the final required shape) using high pressure compressed air.

Neither Type Is Suitable For Private Pools

Neither of these types were particularly suitable for private pools because they both require a full scale site investigation and a specific site design by a professional engineer as well as highly skilled site operatives and expensive equipment.

These factors mean that these types of swimming pool were far too costly for domestic swimming pools.

Concrete Block Walls

Many pools were also built using concrete block walls that were constructed on concrete base slab that also formed the floor of the pool. These were mainly built on a DIY basis or by a builder working for his client.

Some of these pools held water and most did not.

Many different materials were used to try and waterproof the pool walls but most only worked for a time and then some slight structural movement would take place that caused the pool to leak. Once the leak got too bad the pool would be left to fall into disrepair.

Fibre-glass pools were also available but they have always been looked on as a second class cousin to concrete pools because the fibre-glass industry has never really developed a high performance product until just recently.

III. Post PVC Liners

The introduction of PVC liners allowed the development of modular panel pools and concrete block wall pools that were not as rigid, stiff and costly as the concrete tank type pools that had to be designed to hold water.

The invention of the PVC liner has been the most significant thing that has ever happened in the swimming pool industry. PVC liners are now produced to be suitable for every type of pool - from the heaviest used commercial pools - to the pools with the highest environmental loading from ice, snow and the sun.

To be frank, any pool builder that is not using PVC liners is providing their Clients with a sub-standard product!

The only downside of PVC liner technology is that manufacturers of various structural systems have jumped onto the pool construction bandwagon and now produce an array of panel pool products that are fine for above ground pools - but are entirely unsuitable for buried in-ground pools where they are very frequently used.

Structurally, a PVC Liner pool has to be stable enough to be absolutely certain that structural failure will not occur but not totally rigid because any slight cracking does not lead to leaks because the water proofing is provided by the PVC Liner and not the pool structure itself.

There are three important structural implications from this that have never really been fully appreciated by most professional pool builders.

These are:

1. The walls and floor of the pool do not have to be rigidly connected because any slight movement will not affect the waterproofing capability of the liner.
2. The floor of the pool does not have to be rigid because slight movement in the floor will not affect the waterproofing capability of the liner.
3. The walls of the pool can be used to support the concrete slab terracing around the pool because any minor cracking in the walls from the extra load will not affect the waterproofing capability of the liner.

This allows the professional pool builder to provide:

1. A pool floor that consists of levelling concrete covered by a screed finish without any reinforcement or structural connection to the pool walls.
2. Free standing pool walls on a strip footing around the pool.
3. Structural concrete pool terrace slabs around the entire pool perimeter that are supported at one end by the pool walls and at the other end by the firm ground outside the pool excavation.

The concrete terrace slabs around the pool perimter provide two massive benefits:

• They span over the backfilled ground and the sub-soil that has been weakened by the excavation for the pool thus avoiding the traditional subsidence alongside the pool walls
• They rigidly hold the top of the pool walls in position thus allowing Bluepools to adopt its motto "Built for Life".

After years of research and the construction of over 100 pools in the difficult ground conditions of SW France and the UK, Bluepools developed its current pool structural system that takes full advantage of the PVC Liner Technology.