Topic Summary
Each door section has a perimeter frame of steel, aluminum, or wood. Door sections may be subdivided into opaque or glazed panels or have flat surfaces. Some high-end designer doors are made to resemble carriage doors.
Panel doors may have windows or full-vision sections of glass, plastic, or insulating glass. Door sections can be made of steel, aluminum, glass fiber reinforced plastic, or wood, and can be of flush panel or stile and rail construction with opaque or glass infill panels. They can be insulated and weather-stripped to conserve energy.
The door sections are attached on each side to tracks with rollers, and use steel cables attached to the bottom roller to lift and lower the door along the tracks. The weight of the door is counterbalanced by torsion springs on a horizontal shaft located above the door, or by suspended weights or paired coil springs. The last option is the least rugged and is limited to residential garage doors.
Doors may be manually operated or have motorized operators; most residential doors use trolley type operators, while commercial installations usually have jackshaft type operators with heavy-duty motors attached at the head of the door to a torsion-spring counterbalance using belt or gear reduction drives.
Single panel doors operate on spring-loaded articulating-hinge mechanisms with a tilting operation. They are limited to smaller door sizes and are not as common today as sectional doors.
