When space is available above and below an opening into which door leaves can be moved, vertically sliding doors are advantageous. They may be operated manually or electrically. Leaves may travel at 45 to 60 ft /mm. About 11â„2 ft in excess of leaf height must be provided in the pockets into which the leaves slide. So the greater the number of leaves the less space needed for the pockets. Figure 11.69 illustrates a vertically sliding, telescoping door.
Vertically sliding doors normally are counterweighted. About 15 in of clear space back of the jamb line is needed for this purpose, but on the idler side only 4 in is required.
Vertical loads are transmitted to the door guides and then by column action to the footings. Lateral support is provided by the jamb and building walls.