This winter, when the weather turns brutal in many parts of the country, middle-age adults with a love for basketball will be doing more than watching the NBA and NCAA on television. They'll be perfecting their jump shots in the private indoor basketball courts they've built as additions to their homes. That's right, in case you missed it, nailing a hoop to your garage just doesn't cut it anymore. Across the country, flashy indoor half-court basketball rooms with 20-foot ceilings, high-tech lighting and slick maple flooring are becoming fixtures of suburbia. "Five years ago, it was very unusual to build a gymnasium in somebody's house unless it was a full-size gym for some celebrity or some wealthy businessman," says Randy Stafford, president of The Court Company of Germantown, Tenn. "Now there's not a week that goes by that we're not working on someone's athletic room in their house." By this coming February, Larry, a 39-year-old lawyer who asked that his surname not be used, expects to have a custom indoor basketball half-court completed off an addition to his Sands Point, N.Y. home. "I generally love to play basketball and play three times a week when I can," says Larry. The 30-foot-by-50-foot court will allow him and his friends to shoot hoops at odd hours after or before work, on NBA-quality wood floors, which will help preserve their aging knees. "I played ever since I was a little kid," he says. "Now I have kids of my own, and I thought it was a great idea to have for when the weather is bad. Everyone can just go to the gym and shoot hoops." After a pause, he adds, "even though my wife says it's my thing, it's just a great thing for the family to have."