A typical version of an overhead garage door used in the past would have been built as a one-piece panel. The panel was mounted on each side with unequal parallelogram style hinge lifting mechanism. Newer versions of overhead garage doors are now generally built from several panels hinged together that roll along a system of tracks guided by rollers. The weight of the door may be 400 lb (181.4 kg) or more, but is balanced by either a torsion spring system or a pair of extension springs. A remote controlled motorized mechanism for opening garage doors adds convenience, safety, and security.
A standard double garage door is 7 ft. high by 16 ft. wide. Standard single doors are 7 ft. high by 8 or 9 ft. wide. Because the doors are so large, few home centers and only some garage door stores keep many doors in stock, so expect to order one instead of buying it off the shelf. Garage doors are available in wood, fiberglass and steel. Steel doors, like ours, are light, maintenance-free, affordable, readily available, and have an insulating value as high as R-19.
Fiberglass and vinyl garage doors are composite units, combining a steel core behind a fiberglass or vinyl skin. They have also polyurethane insulated base sections, or other type of foam insulation. These premium doors can match steel garage doors, and be a realistic imitation of wood (namely fiberglass units), but they may be more expensive than steel units.