It's one segment of a national remodeling market that's on the mend: Homeowner expenditures on upgrades are projected to increase 3.8 percent from 2013 to about $120 billion this year, according to an analysis by the National Association of Home Builders (NAHB).
"The housing boom in the late '90s was a substantial increase to the total housing stock, so a lot of the remodeling may be to houses that are only 10 or 20 years old," said Stephen Melman, NAHB's director of economic services.
While nationwide the average new single-family home size continues to grow (it hit a high of 2,607 square feet last year after dipping during the recession), some area architects and builders are finding that the taste for large houses has waned.
In Montgomery County, for example, the median size of new homes has declined over the last decade, and more apartments are being built, county planner Brian O'Leary said.
Richard Buchanan of Archer Buchanan Architecture in West Chester said his customers are seeking smaller but still well-made homes, and eschewing some of the grander affectations of the McMansion - like those double-height spaces.
He said customers are often interested in dividing that echo chamber into two separate stories, which are more affordable to heat and offer better sound insulation between bedrooms and living areas.
"We build a floor, and add a bedroom and a bath over the family room, and everything makes sense," he said, "because you've returned to a more traditional pattern of use between private sleeping quarters and more public spaces."
Mark Fox, of Gardner/Fox Associates in Bryn Mawr, said he has also cut a few two-story spaces down to size. While renovations in newer homes are still a small fraction of his business, he said there is demand for certain improvements.
"It's upgrading: The builder put in cheap cabinets and appliances, and we're remodeling those. I haven't had a lot of additions on these homes; they're big enough as it is."
Bathroom remodels were the most-requested renovation, according to the NAHB member survey. Fox said he's also found that many McMansion-dwellers want to update master bathrooms that are fairly new but already dated.
"The master bathrooms are cavernous with big whirlpools and cheap showers," he said. "Sometimes we'll remodel the whole space and make more closet space. Sometimes we'll do a freestanding, claw-foot soaking tub." What people really want, he says, is walk-in showers with glass doors.
He's also built a number of in-law suites above garages. (Multigenerational living has been on the rise for the last decade nationwide; some research indicates that such lifestyles account for as many as one in six households.)
Whether the in-laws or boomerang kids are paying rent - well, that's an open question. Fox said municipalities on the Main Line generally require a letter promising that the apartment won't be rented out before approving such renovations.
"You can't make it an income-producing second unit," he said. "People do it, but you're not supposed to."
Back at Shyamalan's old estate in Gladwyne, now home to three generations under one roof, Seip said it was a case of all of the above.
Those four garage doors stayed, but custom copper paneling was an upgrade from the standard vinyl.
The exterior, which no longer resembles its near-twin a few doors down, received an extensive overhaul to replace the failing stucco and install an elaborate new rainwater-management system to prevent future leaks. Seip also used a mix of different stucco treatments and siding to add visual interest to what had been monolithic walls.
Indoors, he replaced the two-story-high ceiling in the living room with a barrel-vaulted ceiling - still grand, but less echoing. He also eliminated 12 columns in the entryway that had no structural purpose.
While owners of new, large houses are taking on renovations, not all are conservative investments. At the Gladwyne house, Seip added a conservatory, a greenhouse, an indoor koi pond, and a wine room - 3,000 square feet of additional space.
Buchanan said that, for those who have a stucco elephant on their hands, many of the issues can be resolved - but not all.
"If you have a house that was cheaply built with bad materials, with a short-term development mentality . . . it will always plague whatever you do," he said. "We can solve for a badly planned house. But we can't change a badly made house into a well-made house."