It happens suddenly, over a cup of coffee and the morning newspaper, or perhaps as you make your way across the obstacle course of clutter that was once your living room. Your house doesn't fit your needs, and you can no longer deny it.

Time to make a hard decision, one potentially worth thousands of dollars. Should you move, or should you remodel? Dan Fritschen, author of "Remodel or Move," says the typical family faces this decision several times in life. The first milestone tends to be when children arrive. "The standard American lifestyle is to buy a starter house, but when kids come along that starter house may not be big enough anymore," Fritschen says.

Children become teens, and shared accommodations soon feel more like an invasion of privacy than a slumber party. Within a few years a third challenge hits: college. As children move away for school or into their own apartments, the large, teenager-friendly house suddenly feels too big. It may be time to downsize or perhaps convert Junior's bedroom into that hobby utopia you always dreamed about.

Finally, families often face the prospect of becoming caretakers for an aging relative, or perhaps a spouse falls ill and the home needs to become more accessible. Time for yet another change.

Should I stay or go?
The problem is there'is no single motive for each choice and precious little reliable professional help in making that decision. "Contractors won't give you an unbiased opinion because they want the work," Fritschen says. "Real estate agents have a financial stake in you moving. They aren't paid to help you make decisions."

Housing economist Robert Sheehan, president of Regis J. Sheehan and Associates in Woodbridge, Va., says the best place for a family to start their evaluation is with the physical layout of their existing property. Many communities put limits on how big a house can be in relation to its plot of land. "A number of homes are already being built to the dimensions of what can be done," Sheehan says. If your house is as large as it can be, planning an addition would be out of the question; you will need to either work within your existing footprint or move. On the other hand, simply because you are able to expand your home doesn't mean it is a good financial move.

Beware the white elephant
First, get a cost estimate. Then figure how much that work would add to your home's value. Finally, compare your new value with comparable home prices in your neighborhood. "In some neighborhoods, you just won't get your investment back," Sheehan says.

Housing values are falling across the country now, too. Homeowners should tread with extreme caution if they own one of the most expensive houses on the block. "You don't want to create a white elephant," says syndicated financial columnist Ilyce Glink. "White elephants are worthless. You have to look out and say 'I don't want to put $300,000 into a house if in five years the house won't be worth $250,000.'"