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Solid foundation

Is a post-tensioned concrete court right for your facility? It’s time to add that new hard court to your facility. You’ve been hearing a lot about post-tensioned concrete courts, but you’re just not certain. From your research, you’ve learned the courts are durable and fast. But you’ve also heard they’re more expensive. How do you separate fact from hype, and truth from advertising?

Ask lots of questions, say court contractors. It’s the only way to learn. Along the way, they add, be prepared to take notes — and even to be surprised about the durability and overall efficiency of these courts.

A few basics, first of all. There are two different kinds of concrete courts: post-tensioned and reinforced. The two might look and play the same, but there are distinct differences. Reinforced concrete courts generally consist of two half-court concrete slabs, 4 to 6 inches thick, separated by an expansion joint under the net. The slabs are reinforced by steel mesh or reinforcing steel, known as rebar.

Post-tensioned concrete courts, by contrast, are built by creating a grid of sheathed steel cables over which the concrete is poured. After the concrete has begun to set and has reached sufficient strength, the cables are tightened and held permanently under stress. Because the concrete is constantly under pressure, the slab is extremely rigid, and cracking is therefore kept to a minimum.

Once the concrete has cured, a process that takes at least 28 days, the contractor can prep and coat the court. Different prep techniques are used on concrete from those used on asphalt. Then courts are generally covered with an acrylic coating, which may or may not be cushioned or textured, according to the wishes of the owner.

Do Your Homework

With that in mind, it’s time to see how post-tensioned courts are performing in your area, so here’s where the questions come in. Talk to local club and residential court owners, and public and school court managers who have put in post-tensioned concrete courts. Try to get a good cross-section of people — including those whose courts have been in place for a few years. Ask how the courts weathered changes of season and how they stood up to play.

“We built 90 courts last year and 85 out of the 90 were post-tension concrete courts,” says Miles Minson of The Tennis Company in Salt Lake City. “Post-tensioned design is by far the most durable application in the intermountain west due to a large temperature difference between seasons, which we refer to as freeze-thaw cycles. We have post-tensioned courts that have been out for 12 years now and the concrete looks as good today as the day they were built.”

According to Rick Burke of NGI Sports in Chattanooga, Tenn., it’s not just seasonal temperatures that can cause problems in what he considers to be lesser courts.

“Post-tension courts have an advantage in areas where unstable soil conditions create movement, which can lead to cracking,” says Burke. “The post-tension construction using cable under tension holds the slab intact in areas where there is a lot of movement and vast daily temperature swings.”

The lack of problem cracking is a point of pride for builders of post-tensioned concrete courts.

“With properly constructed post-tensioned concrete tennis courts, all cracks will remain hairline cracks, requiring no maintenance for the life of the court,” says Colin Donovan of Denver-based Renner Sports Surfaces. “The cables are generally partially tensioned after 24 hours to arrest cracking during curing. Once concrete reaches a minimum compressive strength, final tensioning is applied to 29,000 psi. If any crack develops prior to the pre-stressing, they are generally no larger than the width of a credit card. Once the cables are stressed the crack is pulled closed because the cables keep the slab under considerable compressive strength.”

Richard Zaino, whose company, Zaino Tennis Courts is located in Orange, Calif., has his own success stories. “We have been building almost every new court with post-tension cables since 1985,” says Zaino. “I recently looked at a post-tension court we built in 1989 for resurfacing and saw one hairline crack. Amazing, after 18-plus years, one small crack. Now, not all courts will hold up this well, but we have found this method to be the best, longest lasting with minimum amount of cracks. We’ve built post-tension concrete courts everywhere, good soils, bad soils. The bottom line is, ‘How can I build the best, longest lasting, crack-reduced foundation?’ And I’ve found out the post-tension reinforcement is the best.”

Worth the Investment

Of course, there’s always that other bottom line that people ask about: How much does it cost? Post-tensioned concrete is more expensive (Burke calls it “the most expensive type of court construction either for new construction or for an overlay”), but many builders say it’s worth the investment.

“Post-tensioned slabs are competitive in price with conventional reinforced concrete slabs,” says Steve Wright of Trans Texas Tennis in Houston. “Asphalt courts may be cheaper in the short term, but will require more frequent maintenance and have a shorter lifespan than post-tensioned slabs. Resurfacing will be similar to other types of hard-surface courts — from three-plus years in high-use clubs to 10 years or more for seldom-used courts.”

The exact price of a completed post-tensioned court will vary, depending on the conditions of the site, the location of the court, the timeline and many other factors. Get bids from contractors and evaluate them carefully. Get recommendations from owners and managers of other courts as well and speak candidly with them about cost and relative value.

Are there drawbacks to post-tensioned courts? Yes — but then, there are with every type of court. Burke finds the concrete slabs to be “very hard and unforgiving to the players. Cushioning these courts is best done with a divorced slip-sheet type of overlay, a system with significant weight.” Simply coating concrete with a build up of cushioning coats, he believes, will only make them more prone to bubbling.

Contractor Experience

Post-tensioned concrete courts require specific expertise on the part of the court contractor. The stressing and tensioning process causes tremendous pressure, and experience in this construction technique is a must.

“Post-tensioned slabs require experienced installers and require careful and documented tensioning,” says David Moore of Cape & Island Tennis and Track in Pocasset, Mass. “If certain procedures are done incorrectly, post-tensioned slabs can have problems; but if done correctly, they are a terrific investment.”

“When post-tensioned courts are built properly, there is no danger of cables snapping,” says Wright. However, owners who want to make structural improvements to a pre-existing post-tensioned court are cautioned not to do it themselves, and instead are advised to seek out the contractor who originally built the court, or another contractor with similar expertise.

“Do not core holes or saw-cut through existing post-tensioned slabs, for example when relocating net posts or adding a shelter where foundations are required,” adds Wright, “as there is danger if cables are cut.”

But don’t let that scare you off, say builders who are proponents of post-tensioned construction. There are lots more happy owners of post-tensioned courts than there have been problems.

“They are more expensive,” says Zaino, “but compared to the replacing or overlaying an asphalt slab, in the long run — with reduced crack repairs, not having to replace the slab, not having to overlay the slab — they are the best value.”

For information about the American Sports Builders Association call 866-501-ASBA (2722) or visit sportsbuilders.org.

From the March 2008 issue
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