The aim of the sub grade is to facilitate fixing the structure to the existing ground. With this in mind the ground is first excavated, then cleared preferably by stripping the earth. The remaining roots are then removed and the soil is treated with a weed-killer. Finally it is leveled then compressed by means of a heavy roller, which hardens it in order to avoid any future collapse within the court. It is sometimes necessary to add a layer of unwoven fiber (geotextile) as a filter to avoid the foundations of the court being plugged by fine particles of clay rising.” Rabbit” sand can perform this function. A drainage network should be installed if the existing soil does not allow the natural evacuation of any water infiltrating the court.
The stones chosen for the foundation layer are hard, non freezable and preferably crushed. The thickness of this layer varies from 12 to 60 cm, depending on the degree of permeability of the foundation base. It is rollered until it is perfectly compressed in order to serve as a foundation of the court. If the stones used are too coarse the surface gaps should be filled with smaller gravel in order to ensure correct levelness and to avoid the fine elements of the surface material migrating to the lower level.
The role of the intermediary layer is that of preserving the humidity essential to clay courts. Stocked water is returned to the surface layer by capillarity. This is 6 to 10 cm layer of cinders or sometimes specific volcanic rock (pouzzolane), must have a finer grained upper layer to enable water to rise to the surface.
Crushed limestone is used to make the coating. The material selected must correspond to technical criteria in term of granulometry (measurement of the elements of which it consists), friability (erosion resistance capacity), water retention capacity and permeability. 60 to 70 tons of material are necessary to make a coating 4 to 5 cm deep after compression.
The coloring layer has three functions-
It must therefore fulfill both colorimetric and granulometric demands. Two tons of crushed brick, which integrate with the surface of the limestone coating, are sufficient to color the court. The construction of a traditional clay court implies respecting this norm which corresponds to the technical recommendations.
The limestone used in clay courts is sensitive to extreme cold. At the end of autumn, the courts are swept in order to remove all the elements, which are not part of the surface (vegetable matter, small stones, and excess crushed brick). The painted lines are removed as soon as they separate from the coatings so that they will not become mixed with the limestone. Once the court has been cleaned new limestone is added to the place where the soil has been eroded, mainly behind the baseline.
After allowing the court to “breathe” for a few days it is advisable to reconstitute a flat, unified and compact surface. The ground is then leveled and rollered. During this series of operations the limestone must be damp but not sticky. Little by little the court hardens. At the end of the cycle the coating, which has hardened, is then colored with crush brick, and rollered again with a large roller. After applying a layer of linseed oil the lines should be painted on. Plastic lines should be repositioned before blocking the limestone. The least used sections will be placed at the back of the court.
Both supple and hard, the court will preserve its initial properties. It is properly maintained, throughout the season, by the members of the club and maintenance personnel.
In order for the court to keep its original characteristics throughout the season, maintenance operations should be undertaken.
Watering the court each evening in order to correctly dampen it is imperative. The court is commonly drenched (while avoiding puddles) for about 30 minutes, hose in hand.
Passing the dragging net after each game enables a perfect distribution of the crushed brick and the limestone which has come loose from the coating. This limits the risk of false-rebounds.
During the season, bits of limestone get separated from the coating and mixes with the crushed brick. This sand, which is impossible to block, causes many false-rebounds. Sweeping the court during the season is therefore is essential. A birch broom is the perfect implement for this job.
Note : Based on French Clay Court
You can observe in the figure of the cross section below:
|1 CMS||CLAY||2/5 - 1/2 INCH|
|6 CMS||RED GRAVEL||2 - 3 INCHES|
|13 CMS||BRICK JELLY||4 - 6 INCHES|
|60 - 120 CMS||BRICK RUBBISH||2 - 4 FEET|
At each stage the area has to be packed well, watered and leveled. Closer the packing, faster the court. The slope has to be given according to flow in that area. The depth of the basic Brick Rubbish Foundation will depend on the soft or hardness of the existing area on which the court has to be laid. In the last stage the clay is sprinkled over the whole area, water is then added and as it becomes a paste it is spread over the area with a leveling stick (normally 3 feet in length).This is similar to plastering walls. Sea sand (fine type) is then sprinkled on top of the leveled clay and the heavy/light hand-roller used. As the area of the court totally dries up the loose sea sand is removed, leaving behind a clean, smooth, well leveled playing surface.
Description of clay: This clay is a sticky mud normally available in lake areas. There are generally two types-black as available in paddy fields and (2) Dark Grey type used for making pots, Ganesh Idols, etc. This Dark Grey type is the one used for tennis courts. This is because you can level it when the clay is wet and it hardens when it is dries.
It is important to ideally water and roll it everyday .The top clay layer needs to be scrapped and re-laid at least once every year. The slight disadvantage is that it takes a longer time to dry when it rains.(i.e. may be an extra ½ day or so.)Cow dung paste is added on top for special occasions for extra binding.
Note: Based on Clay court at Chennai.