Some types of doors take up a considerable amount of side space when they are open. Sliding doors are the worst in this regard. If the door must open to the full width of the building, the track must be extended beyond the sides of the building on an outrigger. Thisarrangement is very vulnerable to wind, and it impedes traffic around the sides of the building.Folding doors waste relatively little end space when open.Overhead segmented doors require ceiling space,which may interfere with lighting and ductwork.Most bi-fold doors block a significant fraction of the upper part of the door opening. However, at least one manufacturer uses side braces that allow its bi-fold doors to open almost to the full height of the opening.
This type is shown in Figure 4. The operating hardware also takes up space. For example, overhead doors need tracks that extend into the space. Cable-operated doors need connections between the winch and the door. Models with selfcontained actuators ease this problem. For example,some bi-fold doors have the motor, winch, and cables mounted on the door assembly itself. Figure 5 shows a compact operator installation.