Contracts can differ considerably from one roofing contractor to another, says Bill Good, executive vice president of the National Roofing Contractors Association.

"They can vary from one-page handwritten deals to 20-page documents written by attorneys that cover every imaginable thing," he says. "The key is to know everything that you're signing." Here is some basic information Good says can be helpful to include:

• Cost
• Payment terms
• Start date
• Expected end date
• Job description
• Materials to be used, with manufacturer's name and length of warranty, if applicable

He also says there should be provisions for change orders or extras. "What happens in the event the contractor discovers something that's not contained in the agreement?" he says. "You'd want to know if there are any extra charges."