When Glen Rosenbaum was a teenager, his parents commissioned a midcentury architect named Arthur Steinberg to design a house in the Meyerland neighborhood in Houston. “My parents, Max and Helen, were really proud of it,” said Mr. Rosenbaum, who is now 66, a tax lawyer and the former board chairman at the Houston Grand Opera Association. “I was, too.”

Enough so that even after he was grown, he still wanted to live there.

At one point, in the 1990s, when he owned a condominium in Houston and his mother was living in the house alone after his father died, they discussed swapping homes. And after she died in 2011, he decided to move back in.

But first he set about renovating the house. William Stern, the architect he hired to modernize it, wasn’t fazed by his client’s desire to remake his childhood home. But when he added a second request, Mr. Stern burst out laughing.

Mr. Rosenbaum, it turned out, wanted to fulfill another long-held dream: to have a place where he could set up the biggest model-train set he could afford.