After more than 20 years, he mastered the trade's techniques, such as mortaring, paving and trenching.

In 1991, he joined the district's park and ancient architecture restoration company, and participated in the reconstruction of the main hall of the Hongluo Temple, marking the beginning of his journey in the preservation of cultural heritage sites.

"It was completely different from what I had been doing before," he says.

The much bigger bricks used in the ancient temple, elegant decorative elements, such as rooftop ornaments shaped like creatures, and the use of glazed tiles were much more demanding in terms of skills, compared with the civilian construction work he'd done.

Fortunately, Cheng got to learn from Piao Xuelin, who was a senior engineer at the Palace Museum and a 15th-generation inheritor of the Xinglong School, a major carpentry and tiling shop involved in building the Forbidden City and other royal buildings in the Ming (1368-1644) and Qing (1644-1911) dynasties.

Right after he cut his teeth on the ancient architectural restoration techniques under Piao's tutelage, he signed up for a three-month training program hosted by Beijing's construction authorities in October 1991.

Cheng systematically studied the evolution of ancient Chinese architecture, especially the royal styles of the Ming and Qing eras.

Although he didn't have a higher education diploma, his practical experience enabled him to readily take in the theories, which he says in turn improved his skills significantly.

Cheng picked up other skills, such as drawing blueprints using computers.