In costructing a clay or fast dry tennis court, a base course of processed stone is installed over a stable and properly - prepared subgrade. The thickness of the base course may vary depending on local soil and climatic conditions, but should be not less than 76 milimeters after compaction.
Aggregate used in construction of the base should be dense graded aggregate (DGA ) , a mixture of stone of various sizes from 20MM down to fine aggregates ( fines ). The proportion of various sizes will differ from one supplier to another. Local stone is often used. Granite or a similar type of stone makes an excellent base because , when crushed , it yields angular particles which grip each other creating a stable base which holds water well. Other materials including slag, washed limestone screenings, washed and crushed shells, cinders, sand or pea rock, also can be used under extenuating circumstances.
The base material should be porous enough to allow water to penetrate after compaction, but not so porous that the water drains completely through. Water should be retained in the base until the court surface begins to dry. Cappilary action then pulls the moisture back into the court surface . To ensure adequete moisture retention, the base material should have a certain percentage of very small particles, called fines. Bases with excessive variation in gradation of stone between layers may interfere with capillary action or water retention.
Clean pea gravel, for example, should be combined with other materials to retain sufficient moisture.
Some possible base materials , when combined with water and compacted, become too solid and lose porosity. For example, some limestone materials become so hard and dense that no water will penetrate at all. For this reason, all base materials should be non water soluble
In areas of freeze - thaw activity, cinders, slag and other lightweight materials may heave and should be avoided. Although cinders, in particular, are very porous but retain water well, they deteriorate over time and react with aluminum nails commonly used to affix line tape. Therefore, they generally should not be used. The most commonly used material is screenings , a mixture of aggregate from 6 milimeters down to dust, which is stable, porous and has excellent material size distribution.
After the base course is completed, a levelling course of screenings is installed. That course should not less than 25 milimetres thick after compaction and graded to the finished slope of not less than 0,28 % ( 0,30M / 110M ) and not more than 0,35% ( 0,34M / 88,00M ) for courts with above ground irrigation, not less than 0,21% and not more than 0,35% for courts with subsurface irrigation.