Hardwood holds up for 100 years or more. Problem is, without regular care, floors get dull and dingy. A screen-and-poly—a surface sanding and fresh coat of polyurethane —is the cheapest (about $1.50 per square foot) and speediest way to revitalize boards, says Don Conner, director of National Wood Flooring Association Certified Professionals Inc.
Full-fledged refinishing, which can take days of sanding and multiple coats of stain and polyurethane, is a must if there are deep gouges or dents, or you want to change the color. Expect to pay up to $5 per square foot, depending on the wood type and how dark you stain. Lay new floor if the wood is too ruined for patching or you're down to nails and can't sand anymore.