Mystery Stains Discolor Retractable Roof at Houston’s Minute Maid Park

Thu August 28, 2003 - West Edition
John Pape

The state-of-the-art retractable roof on Houston’s Minute Maid Park is a lot less dazzling today than during its debut just over three years ago. An as-yet unidentified organism is growing on the exterior of the roof, and the stadium’s principal residents, the Houston Astros, are calling on the manufacturer to correct the problem.

The yellowish-brown discoloration is readily apparent, even from a distance, and is already spawning less-than-complimentary epithets as “Houston’s Chia Pet,” a giant moldy shower curtain, and the world’s largest petri dish. Astros management wants Gen-Flex roofing systems of Maumee, OH, to either fix the problem or replace the roof entirely.

“We first noticed the discoloration last year,” explained Rob Matwick, senior vice president of operations for the ball club. “We think it’s some kind of algae or fungus, but it’s become more and more noticeable over time. We’re basically trying to hold the manufacturer responsible.”

Matwick also noted that fans have commented on the growing problem, particularly since the formerly brilliant white roof is clearly visible to people approaching the stadium on area freeways. Fans attending a recent game noticed the dark stains and several voiced their opinion on what the cause might be.

“I saw it as I was driving up and just figured it was from the air pollution,” Astros fan JoAnn McCollister said. “When the stadium was first opened, the roof was brilliant white. Now it just looks dirty.”

Another stadium regular, Vinny Castaneda, said that he, too, noticed the growing discoloration, and blamed it on Houston’s climate.“It’s hot and humid all the time. Mold and mildew and stuff grows on everything, and I figured that’s what was on the roof,” Castaneda explained. “But now it’s starting to look old and ugly. They need to clean it up.”

Astros officials are particularly concerned about the appearance of the stadium since Minute Maid Park will host next year’s All-Star Game. Both the team and the Harris County-Houston Sports Authority, which owns the facility, want it to look its best for baseball’s showcase event.

Gen-Flex representatives have inspected the roof, which has a 10-year warranty, and the company is currently evaluating the best approach to solving the problem. Options being considered include washing the roof, cleaning and then sealing it with a protective coating, or replacing it entirely.

One of the major issues is whether the discoloration is the result of faulty material or a lack of maintenance. Gen-Flex believes the problem may be a natural by-product of Houston’s air pollution and humid climate, and a good washing is all it needs. That, according to Gen-Flex’s president Jon Apgar, is the responsibility of the Astros.

Apgar also noted that the warranty covers such structural problems as leaks, and not the color or cleanliness of the roof’s exterior. In a recent letter to the Astros, Gen-Flex said that periodic washing will solve the problem, and the cost of the cleaning should be borne by the Astros.

In the same letter, however, Gen-Flex also offered to coat the roof at their expense. Such coating would cost several hundred thousand dollars, but much less than the estimated $2 million to install a new roof.

In a letter responding to Gen-Flex, Astros President Pam Gardner said that their analysis indicates that the problem is the result of defective materials, which should be replaced by Gen-Flex. Gardner also said, however, that the Astros were willing to see if the washing and sealing would be effective.

The 480,000-sq.-ft. roof has not been washed since the stadium opened in March 2000, primarily because the Astros thought that rainfall would be sufficient to keep it clean. The Sports Authority was also under the impression that the roof would require relatively little routine maintenance.

“I don’t think anybody expected you would have to go up there and clean the roof,” Oliver Luck, the Authority’s chief executive officer, told the Houston Chronicle.

Luck went on to say that the Authority supports Astros management in the roof dispute, and expects Gen-Flex to take responsibility for correcting the problem.

Minute Maid Park’s retractable roof weighs 18 million lbs., covers 6.5 acres, and moves at a speed of .356 mpm, or just over 21.4 fpm. The roof is expected to last about 50 years before it needs to be replaced, having traveled an estimated 730 mi. during that time.

The surface of the roof is covered by a thin thermoplastic membrane. Such membranes are typically installed because of their ability to reflect sunlight, reducing air conditioning costs. Gen-Flex has been manufacturing thermoplastic membranes since 1980.

When retracted, the roof is separated into several large segments that stack atop one another. Some observers are speculating that this stacking may inhibit air circulation and promote the growth of the organism when dirt and moisture are trapped between the retracted segments.

Both the Astros and Gen-Flex hope to have the problem resolved before the end of this year’s baseball season.