Q. We've all heard horror stories about cost overruns and delays even if you hire a reputable contractor for a home improvement project. So how can I keep things under control for a kitchen remodeling I'm planning?

A. Start by being clear and detailed about your plans when you ask for estimates. A tile floor in a diagonal pattern, for instance, requires more material (and sometimes more labor) than the same flooring installed in a more traditional pattern. Write a detailed contract laying it all out, and avoid last-minute changes.

See also: 7 steps to hiring a contractor.

Once the job begins, keep in mind that cost overruns can be caused by things beyond the contractor's control: termite damage that comes to light when a floor is removed, for instance. It's wise to budget an extra 10 percent for unforeseen expenses, especially if you live in an older house.

These hidden surprises are usually discovered when demolition is done, typically the first phase of a major project.

But as work proceeds, if you're faced with cost hikes, put the burden of justifying them on the professional who was hired for his expertise — which should include the ability to make an accurate assessment of the job's cost. If he can't give a good reason for an added expense, he "probably doesn't have a legal leg to stand on," says second-generation contractor Tom Silva of the public television show This Old House.

Another big gripe among homeowners is contractors who don't finish on time. This is common because busy contractors (presumably that way because they are good) simultaneously juggle multiple jobs. To ensure yours is done in the allotted time, Silva recommends you insist on a penalty clause in the contract.

"If he says the job will take two weeks," he advises, "say, 'I'll give you three weeks — but at the end of that time, if the job has not been completed to my satisfaction, I will deduct 20 percent from your final payment.' " Formalize specific dates and penalties in writing. Assume that any contractor who balks at such a clause has no intention of finishing in the quoted time frame.

Next: Hire the right contractor in the first place. >>