YOU KNOW WHAT THEY SAY: “All good things must come to an end.” “Everything that goes up must come down.” “Nothing lasts forever.” Right?

For more than a decade, the housing industry has defied those clichés. Year after year, it has outperformed economists' projections. Each year since 2001, it has set new records for building permits, housing starts, and new-home sales. Usually first to lead the country into recession and last to emerge from it, housing shrugged off the 2001 recession; more recently, it even has been credited with keeping the economy from sliding back down.

Some forecasters have been warning for years of a housing bubble about to burst. In recent months, those rumbles have grown louder and more frequent, and they've spread to experts who several years ago dismissed the bubble theory. The skeptics point to extreme home-price appreciation, which has outpaced income growth and made new homes unaffordable to all but the wealthiest buyers in some of the country's largest markets. They cite the number of speculators flooding some areas, looking to get rich quick by flipping a condo or a house—sometimes even before builders finish construction. They say new mortgage products aren't always the answer, especially when they're accompanied by looser lending standards, and warn of mortgage defaults that may come with rising interest rates.

Starting this month, BUILDER will take a critical look at the housing industry's incredible ride, and we'll examine some of the factors that experts say could bring it to an end. The first piece, which starts on page 156, returns to three markets that were hit hard by the last housing bust and reports some of the lessons builders learned—and are keeping in mind now. In October, we'll report on the phenomenon of housing speculation and builders who are fighting back—or going along with the idea. Finally, in November, we'll examine what changes in the mortgage industry could mean to home building, now and in the future.