"A fine home was a symbol of wealth and status, demonstrating that the owner's ancestors had someone in whom they could be proud."

However, there was a rigid hierarchical system in traditional house building in ancient China. The building materials and size of each room were strictly regulated. Hui merchants thus spent most of their money on decorations, especially exterior brick carvings - the more exquisite the carvings, the more powerful the house owner was deemed to be.

Accordingly, a saying popular in Huizhou, "If it takes you 100 days to build, you have a gateway for 1,000 days", emphasizes the importance and complexity of brick carvings in a gateway.

Brick carvers should be able to carve historical figures, opera story scenes and classical gardens, Wu says.

"Studying those ancient works has taught me about the long-lost world of brick carving."

That research includes the history of every ancient gray brick, figuring out the conceptions of the ancient artisans and reconstructing the process of how they worked, he says.

One of the brick carvings Wu repaired won an award for arts and crafts in China, and he became known nationally.

But that was not enough for him.

In 2001 he came across a nine-layer brick carving while repairing a gateway in Shexian, Anhui. This rare top-quality piece puzzled him, and he felt compelled to find out about how it was made.

He consulted a lot of detailed material, inspected many classical ancient Hui buildings and consulted experts in the field.

Eventually he solved the riddle of how the carving was made, the key being that the more layers there were, the more holes were left on the brick's side.

In 2013 Wu finally completed a brick carving depicting a whole family, with 26 vivid figures, well-arranged pavilions and gardens, and it is regarded as a contemporary brick carving of the highest quality.

Though Wu is well known and respected in the world of brick carving, he retains an inner peace that is essential to brick carvers.

"In this craft, you never cease improving your skills. I will pass those skills on to my descendants."