Trex Co. tapped two of its founders yesterday to lead the company as it announced that a third founder, chairman and chief executive Robert G. Matheny, will retire for health reasons.

Anthony J. Cavanna was named chairman and chief executive, and Andrew U. Ferrari was appointed president and chief operating officer. Both had retired from the Winchester manufacturer of simulated wood decking and railing in 2003 but had remained on the board.

Cavanna served as Trex executive vice president and chief financial officer from 1998 through 2003. Ferrari served as executive vice president of marketing and business development from 2001 to 2003.

Roger A. Wittenberg, the fourth founder, left Trex a few years ago to pursue other interests, company officials said. Trex was formed in 1996 by the four former Mobil Corp. executives and went public in April 1999.

"There were four guys that basically built this business up," said Keith Hughes, an analyst with SunTrust Robinson Humphrey in Atlanta.

Analysts said they were unaware of Matheny's health problems until Thursday, and the company did not provide any details about his condition. But Matheny, 59, will remain on the board, "so he's not totally exited from the business," Hughes said.

Matheny did not return phone calls seeking comment yesterday.

The change in management comes as the company is attempting to recover from a series of setbacks.

Last month, Trex reported a second-quarter loss of $1 million because of increases in the price of plastic that goes into its decking. Also, bad weather in parts of the United States kept consumers from building decks.

The company also faced efficiency problems at its production plants as they changed machinery and processes, said John Baugh Jr. of Legg Mason Wood Walker. Trex operates manufacturing facilities in Winchester and Fernley, Nev. A third plant is under construction in Olive Branch, Miss.

With deck-building season coming to an end in September, this is a good time for the management shift, Baugh said. "We're kind of entering the dead season of the deck business, so they certainly have time to formulate their plans for next year," he said.

Trex shares closed yesterday at $26.88, up 33 cents.

Anthony J. Cavanna will become CEO.

Robert G. Matheny is retiring for health reasons.

Andrew U. Ferrari is set to be president.