Finding blisters or bubbles on tennis court surfaces is a somewhat common problem, especially on concrete substrates. Many court owners are baffled by the fact that sometimes the blisters are there and other times they are not. The first thing they do is blame the resurfacing contractor, because it was fine before, and now the problem is happening after the new surface was applied.
Acrylic tennis court surfaces are semi-permeable, or breathable, and allow small amounts of moisture vapor to transmit through them from beneath the slab. However, if there are large amounts of moisture trying to get through, it can create this situation. When a tennis or basketball court was not built with a proper perimeter drainage system to divert rain water away, much of the moisture can end up directly beneath the court. When the sun heats up the surface, the water is drawn upwards in a vapor form. This creates hydrostatic pressure, and can break the bond between the coating and the asphalt or concrete surface. The result is multiple bubbles and blisters on the court surface. Concrete surfaces should also have a 10 mil vapor barrier installed when the court is built, to prevent this from happening. Unlike asphalt, concrete is very dense and has a tendency to create higher levels of hydrostatic pressure. This is why the problem happens more often on concrete courts.
Other than, and combined with poor drainage, surface blisters and bubbles can also become an issue when too many coats of surfacing material are applied. This can happen after many years of resurfacing cycles have been performed. When a tennis court is resurfaced, there are anywhere from 3 to 10 coats of surfacing material applied, depending on whether it is a hard court or a cushioned tennis court surface. The standard resurfacing cycle should happen every 4 to 7 years. At some point, around the fourth or fifth resurfacing, the owner may want to think about having the tennis court contractor remove the existing coatings, back down to the pavement. This helps to minimize the potential for bubbles or blisters, and breathability issues. Also, tennis court coatings contain, or are job-mixed with silica sand for filling voids and texturing the playing surface. This creates non-slip safety, and sets the pace of the game. Sand also breaks the surface tension of each coating layer and allows it breathe better. Thus, it is recommended to specify sand into each coat of material.
In some rare cases, occasional bubbles may appear on a sport surface with adequate drainage. This is most likely to happen during extreme weather patterns that bring continuous rains and over burden drainage systems. If the surface it not subjected to this problem long term, the bubbles usually go down and disappear without further problems. The random bubble can also be injected with acrylic latex to re-adhere the coating to the pavement surface, if needed. A sport surfacing professional can take care of this with minimal cost.
When having a sport court built, make sure the tennis court construction company is familiar with the American Sports Builders Association guidelines for proper sport construction. The best way to ensure this is by contacting a manufacturer of tennis court resurfacing products and asking them for qualified tennis court contractors in your area.