$10,000

Median amount changing plans cost homeowners who added multiple rooms or a story to their home, according to a recent survey by the Consumer Reports National Research Center. More than half of survey respondents experienced cost overruns.

The contractor wasn't necessarily to blame for the jobs costing more than expected. A case of the "whileyas" when the projects are under way—"While you're doing that, could you also do . . . ?"—tended to foster the highest overruns of the 18 remodeling jobs covered in our survey. Seventeen percent of those who did a bathroom addition changed plans and endured a median overrun of $2,250, and 15 percent of kitchen remodelers modified their project, with a median price increase of $1,500.—Ed Perratore | e-mail | Twitter

Essential information: if you're planning a remodel, use our Home Improvement Guide interactive (shown), which lets you click on any room in the house and choose the top appliances and products for interior and exterior jobs.