WHAT YOU NEED TO KNOW
There are generally two types of cracks: structural and superficial. Structural cracks carry completely through the asphalt and perhaps through the sub-base as well. Superficial cracks are commonly referred to as surface cracks. Superficial cracks do not penetrate the entire layer of the asphalt, but only the extreme exposed skin of the acrylic or asphalt surface. Structural cracks are permanent while superficial cracks can be repaired.
As stated above, structural cracks penetrate the entire asphalt or concrete layer of the tennis court. Many times they also penetrate through the entire base and sub-base. Structural cracks may vary in width from 1/64″ to 3″ or 4″. They may vary in length from a few inches to hundreds of feet.
There are many causes of structural cracks. The most prominent is a settling or shifting sub-base (the ground on which the court is built). For a tennis court to remain crack-free, the first area of concern is the sub-base. The sub-base must have a consistent compaction of at least 97%. That is, the material on which the court is built must be compacted to within 97% of its maximum capacity. If different areas receive different compaction percentages, then these areas will respond differently to the same external conditions (such as freezes, saturating rains, weight of equipment and heat). These inconsistencies of compaction will result in the sub-base shifting and adjusting at different degrees and thus in the separation of the distinct areas causing stress and torquing to the asphalt surface, ultimately causing cracks.
The only permanent solution here is to remove the asphalt, re-compact the sub-base and then re-lay new asphalt. If however, the court has finished settling, a layer of fiberglass membrane may be applied over the crack. This will prove effective if the crack has stopped and the ground has finished shifting. However, if the sub-base is still moving, the fiberglass will split just as the asphalt has done. Unfortunately there is no test to see if the ground has finished its shifting so there can be no assurance that the fiberglass will work.
*** Geotechnical borings and cone penetration by an engineering firm is the only way to know the cause and cure for cracks. We always and strongly recommend your hiring an engineering firm to do these boring before any attempt to repair cracks. As humans we are not blessed with x-ray vision and therefore it is impossible, by simple observation, to know the cause of cracks. Without the boring and cone information we are just guessing at what may or may not work in the repairing of cracks. There are a number of “guaranteed” crack repair systems out there and surface overlay systems out there – that, without the proper pre-engineering information – will simply fail. The money spent on doing the borings is the best money you will ever spend if you really want to solve your cracking problem. ***
Also causing structural cracks are organic materials left in the base material. Organic materials will eventually decompose and rot, resulting in soft areas. As the materials (Ex: stumps, roots, lumber, grasses or garbage) degrade, they shrink. This shrinking causes movement of the materials above the organic mass which results in settling and then cracks. These cracks are generally distinguished by a sunken area adjacent to the cracks. When the materials above the pocket of organic material settle down, there is a void left above the degrading material, which causes the sinking of the asphalt surface. Thereby causing cracks.
The solution here is to remove that area that is sinking, re-fill and re-compact the excavated area and then add new base and asphalt material. The problem with this solution is that there is no clear method of determining cost prior to beginning excavation. If the area to be removed turns out to be much larger than expressed by the surface depression, then the cost could be equivalent to building a whole new court. The general solution is to patch with fiberglass and then fill the sunken area with asphalt or acrylic patch material. Unless the problem area is very severe, this should last from 2 to 5 years enabling further considerations and budgeting to permanently solve the problem.
Still another cause of structural cracks is improper compaction or application of either the base stone or the asphalt itself. Again, the most important and critical area of a tennis court is its base under the asphalt or concrete. If the base is not of adequate thickness, density, compaction and consistency, then everything laid upon it will be inferior. The old axiom that “you can’t paint jello” applies here. If the material below the asphalt or acrylic surface is not solid, then no amount of money or material above the surface will solve the problem. You can’t have movement below asphalt or concrete and not expect to have cracking in the asphalt or concrete. This applies to the acrylic materials, also. If the asphalt is not solid and firm, then the acrylic material laid upon this asphalt will not be without eventual cracking.
The key is to make sure that every consideration be taken to ensure proper integrity with the base materials. Every area of the country is different, so it is necessary to locate local paving codes and perhaps inquire through a civil or paving engineer what type of bases and quantities of materials are needed in your area to ensure against a weak base. The general rule of thumb requires 5″ of base material (such as limestone or crushed granite) topped by 1 1/2″ to 3″ of asphalt.
SUMMARY OF STRUCTURAL CRACKS:
Structural cracks can be prevented by proper initial construction but they can not be repaired permanently unless the area affected is removed and then replaced. This process is usually very expensive and not cost effective.
The most important aspect of any crack is whether or not it is a hazard to the people playing tennis. If the crack is upheaved or sunken to the point where a player may trip or slide, resulting in a loss of balance, then the area must be repaired. If, however, the crack is level and flat with no discernable footing problems then the crack (with the knowledge that it will eventually get worse) is nothing more than an eye sore and may be corrected at a later date.
There is only one circumstance where we can guarantee the repair of a structural crack. That is when we remove the area affected and replace it with new sub-base, base and asphalt material. Any other method such as patching, fiberglass, rubber or overlaying will not keep the ground from moving and therefore not be able to prevent to re-occurance of the cracking.
The first consideration in repairing structural cracks is safety. That is, does the crack present a health or injury potential to the people playing on the court? If so, then immediate attention must be placed on repairing this crack. The second consideration is money. Generally to remove and replace base materials will cost 3 or 4 times as much as filling and patching. Every situation is different, as every crack is different, but generally structural cracks come back. The question is not if, but when.
Superficial cracks penetrate only the outer skin layer of the asphalt or the acrylic. These cracks are generally caused by the drying out of the asphalt or the acrylic materials. In some instances they can be caused by spilled soft drinks, gasoline, insecticides, tree droppings, etc. These cracks are always very fine (1/32″ or less) and random in their path. Superficial cracks are most common around the baselines and sitting areas. However, they may be located anywhere on the court.
Superficial cracks are easily repaired. Although they do not pose immediate concern, it is very important to note that if left unattended for a long period of time (over six months), especially, in the winter months, these cracks can become structural cracks.
In the winter when it rains or snows, the water will settle into any small cracks in the court surface. If this water then freezes, the expansion of the freezing water will cause the crack to widen. A succession of freezes and thaws will turn a relatively small superficial crack into a structural crack in a matter of months. Every fall these superficial cracks should be filled with acrylic surface material to prevent water from accumulating. Otherwise, come spring, the court will be in much worse shape.
Generally superficial cracks require no more than a layer of fiberglass and some patch material to be applied during any standard resurfacing job. The most important prevention of these cracks is to have the court surfaced at least every 4 years so as to prevent the drying out process that takes place after months of being exposed to the sun’s ultraviolet rays. These resurfacings will prevent the superficial crack, they will also help to prevent the turning of a superficial crack into a much more costly structural crack.
As with any product, preventive maintenance is always the cheapest form of repair. Weekly checks of the court surface for small slits or cracks could save future dollars. Remove any spilled soda or gasoline as soon as it becomes evident. Use squeegee or Rol-Dri to remove standing water after a rain, as this sometimes will erode the surface and cause cracks. Above all, address problems as soon as possible. In many instances superficial cracks needlessly become structural cracks. A few dollars worth of materials and usually less than an hour of work will save hundreds of dollars in future repairs.
By Gary D. Whalen
Gary D. Whalen and The Whalen Company have built tennis courts for 40 years in Florida, Georgia, North Carolina, South Carolina, Tennessee, New York, Ohio, Alabama, Connecticut, West Virginia, Virginia, Dominican Republic and Maryland.