Building on the strongest foundations
We know that when it comes to building a tennis court, quality starts at the foundations. A well-engineered foundation is as essential to the performance and durability of a tennis court as to any other structure. That’s why we pay an enormous amount of attention to the part of the court that you will never see.
Cotswold Tennis Courts have a well earned reputation for outstanding durability and we find ourselves cleaning courts that we built more than 20 years ago and are still in good condition and frequent use today.
Over the years and throughout the different seasons, your tennis court will inevitably be subjected to many different stresses and climatic conditions. These mainly concern the sub-soil on which the foundation is built, and can include frost heave, shrinking or swelling clay, settlement, ground loading above the surface, problems caused by tree roots or weed growth, flooding, faulty or inadequate drainage and other types of ground movement.
The degree to which the performance and durability of the playing surface will be affected by these forces depends on the site conditions and the type and depth of construction.
Certain sub-soils are far more prone to the two main causes of serious problems, frost heave and clay shrinkage, and clearly it is important to determine site conditions before designing the construction.
Frost heave is caused when frost penetrates into susceptible sub-soils that include a lot of fine silty material. The particular pore sizes of these soils draw water by capillary action into the freezing zone, causing ice ‘lenses’ to form which then expand and push up towards the surface. The longer and deeper the period of frost penetration the greater is the effect. After thawing, the surface will eventually settle back but the displacement, and subsequent inconsistent settlement, will leave undulations on the playing surface.
Many clay soils are prone to swelling when hydrated, and shrinking and cracking when dehydrated. This will often show as cracking in a lawn during a dry summer. Such cracking and settlement or swelling will transmit through to the surface if an insufficient depth of foundation is provided. The table below shows how minimum foundation depths are determined by the make up of the soil on which the tennis court will be built. The figures are only a guide and in practice we adjust them to take into account specific site condition and local knowledge.
A tennis court built with foundations that are less than the code of practice specified depths is unlikely to be covered by insurance for ground movement or frost damage.
Getting it right from the ground up…
We build our foundations using hard, clean, well-bound, non-frost-susceptible aggregates. The total construction depth (foundation plus surfacing) is critical for several reasons:
The greater the depth the less chance of frost penetrating into the sub-soil, and the less chance of tree roots distorting the surface.
The thicker the foundation the less the court is affected by stresses on the surface. For example doubling the thickness will reduce the effect of stresses at formation level by a factor of four.
Using thicker foundations gives a greater load-bearing capacity. This can allow us to use heavier machinery that is more economic and provides a higher quality surface with better surface tolerances and more even texture giving more even ball bounce and longer life.
We build to specifications that exceed the minimum standards laid down for the tennis court construction industry.
Just for the record, the standards for virtually perfect ground conditions are as follows:
Foundation: 150mm consolidated for porous playing surfaces and 200mm for impervious playing surfaces
Macadam surface course 32mm compacted depth
This gives a total minimum construction depth of 200mm, which is well below the 450mm that is generally regarded as the potential frost penetration depth for most parts of the UK. In the Cotswolds that figure is much more likely to be about 300mm. We use our experience of building tennis courts for more than 100 years to achieve the right balance between achieving best value for money and minimising, if not totally eliminating risk.
The figures are only a guide and in practice we adjust them to take into account specific site condition and local knowledge.