Tennis Technology

In recent years, a renaissance of sorts has taken place in tennis. Clay courts are making a come-back. For years these courts have been maligned as too expensive or time-consuming to maintain, yet well documented concerns about injury prevention, safety and player comfort have lead court owners and facility managers to reconsider the many positive aspects of this type of court. Despite this renewed interest in clay courts, there is still a great deal of confusion as to what clay courts really are.

This confusion is understandable since the materials and methods of clay court construction are highly variable not only across the Unites States, but throughout the world. In Mexico and much of Central and South America, for instance, hundreds of natural clay courts are built every year. In the United States, meanwhile, most so-called "clay" courts actually contain no clay at all. Likewise, at the French and Italian Open events, two of the world's most popular clay tournaments, there are no clay courts either. Knowing this, it is only natural to wonder what the term "clay court" really means.

Strictly speaking, clay courts are only those courts with natural clay surfaces. However, since natural clay courts occurred early in the evolution of tennis courts, other types of courts developed later that played like clay courts were called "clay courts." Because of this, courts such as fast-dry and synthetic clay surfaces are also generally lumped into the "clay" category, though they are not technically clay courts. Perhaps a better term for this broad category would be "clay and clay-like courts" or, more simply, "soft courts." To better understand these differences, it is helpful to look at the history of clay courts over the last century.

The Early Years of Clay Courts

Even though tennis was established as a lawn sport in 1873, by the end of the 19th century clay courts were steadily gaining popularity. Like turf courts, clay courts were comfortable to play on. They were soft but firm under foot and cooler than other court surfaces such as sand, asphalt or concrete which were less popular among players at the time. Clay courts had an advantage over grass in that they did not require an intense regimen of watering, fertilizing or mowing. Early clay courts were typically designed to be flat, with a drainage system below the surface intended to quickly dry a court after a rain. In reality, however, these courts often took two or three days to dry out after even short periods of precipitation.

In 1909, a British firm named En Tout Cas (its name was taken from a French idiom meaning "all weather") solved the drainage problem by replacing the clay surface course with a blended mixture of crushed brick. This new material played similar to clay despite its considerably more granular appearance. The crushed brick surface allowed more water to run through the surface of the court drying the surface more quickly after a rain. Thus, the concept of the "fast-dry" court was born. In other parts of Europe during the 1920's, the concept of the fast-dry court spread quickly. Interestingly, in countries such as France, Spain and Italy where the weather was milder and precipitation significantly less, the coarse, gritty texture of the British style surface dried out too fast and therefore was difficult to play on. In these locations fast-dry surface courses were generally shallower, consisting of powdered brick or red sand, making these courts appear more like natural clay surfaces. In fact, these types of fast-dry courts are often mistakenly referred to as "continental clay" courts.

American Clay Court Innovations

In the United States, during this same period, the European style fast-dry courts quickly became popular, and contractors began to import the British material. Since the crushed brick was bulky and expensive to ship, American contractors began to experiment with locally produced fast-dry mixtures. In 1928, H.A. Robinson, a New York court contractor, built an American style fast-dry court using finely crushed stone screenings. The uniqueness of Robinson's material was that it was derived from a naturally occurring green stone. This green fast-dry material, marketed as Har-Tru (a name taken from Robinson's initials and the true green color of the material), and later under other proprietary names, quickly became the preferred soft court surface here in the States.

Over the next 50 years, American contractors further refined fast-dry and clay courts. For example, it was soon established that fast-dry courts had limited porosity, and, in fact, had to be sloped in order to shed excess water, thereby decreasing drying time. Sloping the court allowed contractors to eliminate the use of subsurface piping and reduce the depth of court base, saving considerable amounts of material and labor. Later developments such as automated sprinkler systems and mechanical rollers reduced maintenance efforts. In the late 1970's and early 1980's the demand for soft courts in the developing sun-belt regions of Florida, Arizona, and California lead contractors to develop sub-surface irrigation system. This innovation reduced water consumption up to 85% and maintenance by as much as 30% to 40%. Perhaps more than any other technical development in the clay court sub-surface irrigation was to bring back the popularity of the clay court by making fast-dry courts more affordable and geographically accessible. As contractors developed a more sophisticated understanding of how fast-dry courts worked, many of their innovations were adapted to clay courts. Improvements such as sloping the court, the use of automated irrigation, and even the use of thin fast-dry top dressings over clay surfaces made clay courts significantly more manageable and, therefore, still appealing to players.

Clay Courts go Synthetic

Over the years, contractors have been continually looking for ways in which to replicate the slide characteristics of clay courts by using rigid pavement structures as a way to avoid the maintenance associated with natural clay and fast-dry courts. In the late 1960's and early 1970's both European and American companies were again attempting to replicate the feel of the clay court. This time, however, they were looking not to natural materials such as crushed stone, brick or sand, but rather to processed materials such as synthetic rubber, polyurethane, and polypropylene textiles. These new courts were to become known as "synthetic clay" courts.

By the early 1980's two distinctly different types of synthetic clay courts were being constructed both in Europe and the United States. The first type consists of a polyurethane bound rubber granule cushion course on top of an asphalt or concrete pavement that is dressed with a thin layer of loose synthetic rubber granules. The second type consists of a textured carpet matting adhered to an asphalt or concrete pavement. Synthetic rubber granules are then spread over the carpet surface to provide a clay-like appearance and slide characteristic. Both of these types of courts were developed primarily for use in indoor tennis where excessive moisture from fast-dry or natural clay can cause severe building damage. While these types of courts are fairly unusual in the United States, there are several thousand of them in use across Europe.

Today's Clay Courts and What's Right for You

Today, all three types of soft courts are still built today in great numbers. Fast-dry type courts comprise the largest group of soft courts built every year, followed in number by natural clay and then synthetic clay courts. When deciding what type of court is right for you there are four major points to consider.

First, you need to consider your geographic location. It is important to know that regional traditions still play a strong role in determining what types of courts are built in your area. It is good to know what court materials are available locally and what methods of construction local contractors are familiar with. If good clay is available it might be cheaper to build a clay court than a fast-dry or synthetic granular court made with materials shipped over great distances. Climate should also be considered before choosing what type of court to build. For instance, if you are located in a very dry climate, you might want to consider using a sub- surface irrigated fast-dry court. Remember also that local building practices are often slow to adapt to new technological developments. So be careful not to rule out a particular type of court simply because it is not built in your area today.

The second point to consider is budget. Generally speaking, clay courts typically cost less than asphalt or concrete courts due to their less complicated methods of construction and less expensive materials. Depending on your geographic location, specific site conditions and number of courts being built at the same time, natural clay and fast-dry courts with above ground irrigation systems typically cost between $18,000 and $24,000 per court. Fast-dry courts with subsurface irrigation systems are usually more expensive due to their more involved construction, ranging between $25,000 and $30,000 per court. Synthetic granular courts, depending upon the availability of materials and an experienced contractor, usually cost between $25,000 and $30,000 per court for outdoor installations, and $15,000 to $18,000 for indoor installations. Since all soft courts require some sort of regular maintenance, you need to weigh how much you want to spend initially versus how much you want to spend on annual up-keep. A court with above-ground irrigation might be less expensive to construct than a subsurface irrigated court, but more expensive to maintain over the life of the court because of its greater need for water and daily maintenance. Synthetic clay courts, meanwhile, require no watering at all and significantly less maintenance.

The third point to consider is the specific condition of the proposed court location. You will need to know the soil conditions and whether the ground is stable and reasonably well drained. In situations where minor settling of the ground might be a problem, a fast-dry or natural clay court would be a good choice as these courts are somewhat flexible, forgiving and easily repaired. Subsurface irrigated fast-dry courts are generally less tolerant of shifting soils because they depend upon a uniform distribution of moisture across the court. Therefore, settlement might result in localized dry spots. Synthetic clay courts, because they are built atop rigid pavement bases, cannot tolerate instability. If you are planning a natural clay or fast-dry court and your site is poorly drained, it would be best to consider a subsurface drainage system to prevent the court from being saturated from below. Other points to consider regarding site specific issues include access for construction, daily and annual maintenance operations, and the allocation of storage space for maintenance equipment and additional surface material. Not to be forgotten is an adequate and dependable water supply if you are considering natural clay or fast-dry.

Finally, you should consider the aesthetics and playability of your proposed court. There are a variety of surface materials available today which offer a great range of colors and textures. Fast-dry products and top dressings are available in brownish tans, gray greens, deep burgundies and orange-reds. They also come in different grades from very fine to coarse, which can be used to adjust the speed of play and amount of slide on the court. Synthetic clay courts currently are available in blues, greens, tans, and reds. The degree of slide on a synthetic clay court can be easily adjusted by increasing or decreasing the depth of granules over the surface. So, if you like the play of clay courts, the good news is that there are a number of different court options available to you. But remember, they are not all the same. 

by Andrew R. Lavallee, ASLA