Post 324 — by Gautam Shah
Sliding doors have been in use since perhaps Roman times. Channels carved in stone have been found at Pompeii. Sliding doors are preferred in many situations as these do not disturb the space. Simplest sliding doors have one shutter, moving over a wall, panelling, side-lite or into a cavity (pocket doors). Functional slide doors have dual shutters, each moving in opposite directions. In a stacked door system the shutter (each on a separate track), slide to form a stack on one or both ends. Wardrobes and verandahs use a dual systems of sliding+hinged doors combination where in case of four door system two ends shutters are side-hinged and middle two doors slide behind or over the hinged doors. Such a system is also called bypass door system.
Sliding doors unlike a pivot or hinged doors are not hung from a side, but its entire width is hung on top or supported at the bottom side. For this reason the door leaf has no stresses, and even if very wide or heavy can be moved.
Sliding doors with top hung systems have two or more sets of wheels, or a slider mechanism of ball-bearings, moving over a rail or in a channel guide. The linear support system distributes the weight of the door leaves. To prevent sideways displacement of the shutter a continuous or intermittent guide is placed at the bottom. Very heavy doors have bottom supported system with wheels moving on floor, rails, or channel track. Very tall and wide doors also have extra sideways rollers to maintain the position of the shutter against sideways thrusts.
Pocket doors are sliding doors that slide away from the opening, into a specific cavity, a niche parking area. The niche is hollow space in the wall thickness or concealed by a panel or partition.
Bypass doors have two or more sliding shutters that move past each other. The shutters are commonly used for closets and shop or showroom cabinets. The shutters overlap slightly to seal the joint gap.
Nominal sliding doors do not provide 100% opening gap, whereas the Folding and sliding combination doors offer it. One of the shutters, usually the end one, is a sliding entity, and onto this 1 or 2 shutters are side hung with hinges like folds of an accordion.
In another system end shutters have a top and bottom pivot-hinge for attaching the next shutter. The pivot-hinges have extra axial pins extending out, and a mounting of a ball or free wheel to slide in a track. Such doors are used for closets and as space dividers in auditoria, indoor sports facility, banquet rooms.
Bifold doors are paired doors that are hinged together to fold onto one another. The end shutters are hung with hinges and also have a top-bottom sliding pivot as part of the bottom hinge. These are often mounted on a track that hangs from the head. It is a popular configuration for wardrobes and cupboards. It is also used for patios, internal doors’ partitions such as between dining and drawing room. These doors, when open, occupy very little room space. The doors have a tendency to sag and have a weak lateral strength, so are not ideal for external use. Internal doors are intentionally made to be very lightweight.
Accordion doors are multi fold doors, almost like tambour doors but with vertical slats or shutters. The slats have a backing of canvas or flexible plastic. The shutters, have flexible metal (spring steel), plastic (Teflon) straps or regular hinges. The end, top and bottom hinges often form a sliding pivot mechanism. The door system is often designed to negotiate curvature or form angular or polygonal shape. Kashmir style room dividers are an example of accordion system.
Collapsible gates are formed of several vertical members which are joined together by small length members forming a scissors like pin joint. The top and bottom ends of the vertical members are housed in a sliding channel with or without wheels. The vertical members can be pulled to open out to a lattice form or pushed together to collapse into very small width. Collapsible gates are single or double sided and portable type. The portable types are used as a folding barricade. Collapsible gates are mounted with an accordion like folding panels and piano hinges to form an opaque shutter. Collapsible gates were once used in elevators, public passages, etc., but are now not allowed in elevators.
Canopy or garage doors are also called up & over doors, This offer a clean width for parking an automobile in a garage. The door moves up and takes a horizontal position very close to the ceiling line, allowing full width of opening and without the shutter occupying any floor space. Most such doors are automated, so can be opened or closed through a remote control. The door is called canopy Door because when this is mid pivoted for counter balancing, a section of it remains outside forming a shed against weather or sun.
Rolling shutters became popular to cover up large openings of industrial buildings, warehouses and wide glass fronted shops. These are fabricated with horizontal or slats that are loosely inserted into one another to form a movable joint or hinge. All such slats are held in side channels, and roll up into a cylinder at the top. The slats are fold-shaped or have concave curvature to add to its lateral stiffness. The rolling up into a drum form tightens a winding coil spring which helps in quick shutting of the door. Very small sized rolling-up shutters are used on TV cabinets, wardrobes, cupboards, showcases, dumbwaiter or service elevators. These do not have coil springs. Very wide and very tall, that is heavy shutters are opened and closed through a winding ‘timer chain’ with sprockets.
Tambour Door is made of narrow horizontal slats that are joined together by rope or strap at the middle or ends, or by a continuous backing of flexible material like canvass or leather. These doors either roll up or down, or sideways along the tracks or channels. These are typically used in TV cabinets, jewellery boxes, small bureaus, and cabinets.