Although cork floors should last years with basic maintenance, refinishing a cork floor can extend its useful life. Before attempting this project, be sure that you have solid cork floors and not cork veneer floors. Veneer floors cannot be sanded before refinishing, making it impossible to remove scratches that have damaged the underlying cork. Also, some cork is not finished using polyurethane, but simply is oiled before installation. This type of cork flooring should only have oil reapplied and not be traditionally refinished.
Remove any baseboards around the floor, carefully using a pry bar. Number the back of each piece with a pencil to indicate its position in the room.
Sand the floors with an electric floor sander fitted with a 60-grit sanding pad. Cork flooring is extremely soft, so keep the floor sander moving to prevent damage.
Load the floor sander with a 100-grit sanding pad and sand the floors again. It's important to make sure the cork surface is smooth, but limit the sanding as much as possible to prevent damage.
Vacuum the floor to remove all sanding dust and debris. Remove any remaining residue with a tack cloth. Get the floor as clean as possible to ensure a smooth finish.
Apply the polyurethane finish using a 4-inch exterior soft-bristled paintbrush. Start from the side farthest from the door and work your way toward the exit. Overlap your passes, working from wet to dry to minimize brush strokes.
Allow the polyurethane to dry at least 12 hours, or according to the manufacturer's recommendations.
Sand the finish as lightly as possible, using an electric floor sander fitted with a 00-grade wool pad, to remove any imperfections. Clean the floor with a tack cloth.
Apply a second coat of polyurethane with the 4-inch brush. Allow the finish to dry. Apply additional coats of polyurethane, allowing each coat to dry thoroughly before applying the next, until you have achieved your desired finish.
Reinstall the baseboards with finishing nails and a hammer.