A garage door is a large entryway on a garage that can either be opened manually or by a powered opener. Garage doors are large to allow passage of automobiles. Garage doors normally raise or roll upward, instead of sliding or swinging, in order to save space. The door is typically spring-loaded or counterbalanced to offset its weight and to reduce effort required for opening and closing. Doors may be insulated to prevent loss of heated or cooled air.
Overhead garage doors consist of several panels hinged together that roll along a system of tracks guided by rollers. The weight of the door is balanced by either a torsion spring system or a pair of extension springs.
Not including doors that opened for buildings which housed horse drawn vehicles, the first garage doors found in the U.S. occurred at the beginning of the 20th century. Some American manufacturers had catalogs featuring a single panel door. Three types of garage doors are
- Single Panel Doors. From the closed position a single panel door will slide up and overhead on rails to the fully open position. A disadvantage of monolithic panel doors is that the swing up arc of the door occurs partially outside the garage. This means a vehicle must stop and park several feet in front of the door to avoid being hit by the garage door when it is opened.
- Sectioned Doors. Sectional doors are usually constructed of six to eight panels and slide up and overhead. Sectional doors occupy exactly the same amount of internal garage space as a monolithic door. They, however, do not required external space to operate.
- Roller Doors. Roller doors are usually constructed of corrugated steel. A typical single car garage roller door will have a preloaded spring inside the rolling mechanism. The spring reduces the effort required to open the door.
Garage doors can be made out of many materials, but steel, aluminum, wood, cooper, glass and vinyl are the most popular materials. They each have benefits and drawbacks.