Project runaways.(planning home-remodeling projects)

Odds are high that something will go wrong with your next remodeling project. How do we know? We asked 17,129 readers about their experiences with 18 common projects, from painting a room to building an addition--almost 30,000 projects in all. How many respondents had at least one problem? Forty-four percent.

You may be able to avoid their fate with a little extra planning and patience, whether you hire a contractor or do the work yourself. Here's how:

Spend time to save money. Buying the wrong products, unexpected incidentals, and "surprises" such as delivery charges and debris-removal fees boost costs. More than 25 percent of respondents said they paid for poor planning--a median of $625. Even seemingly simple projects such as interior painting cost readers a median of $280 extra because of various issues.

Make a thorough plan, and stay with it. One in 10 readers said they changed their minds during remodeling ("change orders" in contractor speak). Of those who runaways made changes, 37 percent spent a median of $2,000 extra. For people doing big additions, that number ballooned to $10,000.

Hire a realistic contractor. Almost one in 10 readers told us they spent more than budgeted because their contractor underestimated expenses, did shoddy work, or failed to anticipate code requirements. Lowball bids are more common in competitive markets. "In today's climate, contractors are loath to lose a job by being too gloomy about a project," says Bruce Irving, a home renovation consultant in Cambridge, Mass. "If a guy underbids, ...