THERE WAS A TIME WHEN 9-foot ceilings and walk-in closets were the stuff that luxury upgrades were made of. That was before the housing market went on steroids and super-sized homes with cathedral ceilings and three-car garage-mahals became the new gold standard.

Size still matters in the world of decadence—but today, so does substance.

“Ten years ago our median price was in the low $300,000s, whereas today it's over $600,000 nationwide,” says Jed Gibson, vice president and director of architecture for Toll Brothers in Horsham, Pa. “Part of what's driving that price are the features people are putting into their homes. They aren't just going for bigger spaces, but also nicer things: high-end appliances, upgraded flooring, better tile, and good lighting.”

The luxury market is shifting, in part, because of who's buying. Americans ages 50 and over now control more than 75 percent of the nation's wealth and possess more than 50 percent of all discretionary income. Their ranks are increasingly made up of iconoclastic baby boomers who are pooh-poohing cookie-cutter opulence in favor of more personalized spaces.

Which features resonate most with this upscale set? Here are some tips for winning the hearts and wallets of these coveted home buyers.

1. FLEX YOUR MUSCLE Flex spaces that can be tailored—as extra bedrooms, playrooms, home offices, studios, fitness rooms, etc.—go a long way, says Gibson. This custom option appeals especially to members of the sandwich generation who are in their peak earning years and may need additional living spaces to accommodate move-back kids or older parents. (In a 2004 survey of baby boomers conducted by Del Webb, 40 percent of respondents anticipated that their adult children would move back in with them, 30 percent that their parents would move in.)

Toll Brothers has responded with a menu of structural options in its Signature line of homes topping 4,000 square feet. One plan includes a 30-foot-by-14-foot chunk of space that can be alternately constructed as a conservatory (featuring arch-top windows), a great room, a media room, or a private guest suite with a study and bath.

In this same vein, detached dwelling units such as accessory casitas, cabanas, and carriage house suites are hot properties for guest retreats, mother-in-law units, or home office studios for semi-retired boomers starting second careers.

2. EMBRACE THE OUTDOORS Outside has never been so in. A recent survey on home design trends conducted by the American Institute of Architects confirms that buyers in all markets (not just warm climates) are clamoring for floor plans that maximize views, breezes, and solar exposure with integrated patios, loggias, lanais, interior courtyards, decks, and wrap-around porches. And today's al fresco living spaces are appointed with the works: gourmet grills, woks, wine and/or keg refrigerators, showers, saunas, and fireplaces, as well as old standbys such as water features and dining furniture.

At the same time, elements of the natural world are making their way indoors, creating new options in color and texture beyond the granite standard. Materials such as exotic hardwoods (e.g., zebrawood and wenge), soapstone, limestone, and slate are in vogue. So are sustainable flooring materials such as bamboo, cork, and wide-plank boards re-purposed from salvaged lumber.