Which type of door is not considered a specialty door?

Interior doors are not considered specialty doors because they serve a common purpose and are standard components found in most buildings. These doors typically provide privacy and access between rooms in residential and commercial constructions. They are mass-produced and do not have unique features that differentiate them from one another, making them a regular fixture rather than a specialized item.

In contrast, folding doors, double doors, and sliding doors are classified as specialty doors due to their distinct functionalities and design applications. Folding doors, for instance, are designed to save space by folding out of the way, making them ideal for areas where conventional doors may be impractical. Double doors often provide wider openings for enhanced access, especially beneficial in commercial or institutional environments. Sliding doors, on the other hand, are used in scenarios where space is limited, allowing for a seamless transition between indoor and outdoor areas without requiring clearance for swinging open. Each of these types has unique properties and applications that set them apart from standard interior doors.