This section is from the book "Modern Buildings, Their Planning, Construction And Equipment Vol2", by G. A. T. Middleton. Also available from Amazon: Modern Buildings.
Where openings are too wide to be fitted with one door, Double Doors, or a Pair of Doors are fixed. These are constructed separately as single doors, and the styles coming together are called Meeting Styles. In single doors the style to which the hinges are attached is called the Hanging Style, that containing the lock the Striking Style. A rail between the top and lock-rails is called the Frieze-rail.
In openings which are too wide for a single door and not wide enough for double doors it is usual to put a Double-Margin Door, which consists of two narrow single doors joined together at their meeting styles, and as the construction is a little more complicated than that of the ordinary door, a sketch of the meeting styles is shown in Fig. 129. The two halves having been prepared in the ordinary way, the meeting styles are ploughed for tongues, and have three mortises made as indicated, and also a small rebate on each side of the meeting edges. The outside styles are knocked on dry, and the rails are glued and wedged into the meeting styles. The ends of tenons and wedges being cut slightly back from the face, the tongues are glued in and the styles cramped up, hard-wood folding wedges being glued and driven into the mortises as shown. When all has set the ends of the wedges are cut off, and the door is completed in the ordinary way. These doors may be strengthened by a flat iron bar let into the top and bottom rails.
The styles of doors are sometimes reduced in width in the upper portion, the diminishing usually taking place at the lock-rail, which is then cut with a bevel shoulder, as shown in Plate IV. This form of style is generally adopted with doors which are glazed above the lock-rail.
It is sometimes desired to construct a door in such a position that its presence is not noticed, and where an ordinary opening and door would spoil the effect of wall decoration or framing. In this case what is known as a Jib Door is used. It may consist of an ordinary framed and panelled door, but is so arranged that any decoration or mouldings on the wall may be continued uninterruptedly across its face.
The process of fixing a door into its frame or linings is known as "Hanging." Main entrance and all interior doors are generally hung on "butt hinges, which have square or butt ends and are let into the wood, as distinguished from hinges fixed on the surface.
There are two ways of arranging the swing of a door when hanging, - one known as "Close-joint hanging," in which a close joint is maintained between the door and lining, in all positions of the door; and the other known as "Open-joint hanging," in which there is a varying opening between the door and lining. The difference is effected in the arrangement of the hinge, as shown in Fig. 130. When hanging a door it must first be marked out from the opening and shot to size, joint allowance being made according to the class of door. With a well-seasoned pine door nearly 1/8 of an inch may be allowed on each side, and 1/16 of an inch at top, but with a polished hard-wood door not more than 1/32 of an inch at sides and top, the bottom allowance in each case depending upon whether thick floor covering has to be provided for or not. Having marked out the positions of and fitted and screwed on the hinges, they are opened out flat and the door placed in the opening, two small wedges under the bottom and one on each side near the top being used to bring it to its exact position. The sinkings for hinges are then marked on the linings, the door removed, and the sinkings cut out. The wings of hinges are then fitted into their places and one screw fixed in each, the door being held half open on the wedges. The swing is then tried, and if any adjustment is required it can be made by a slight alteration in either the top or bottom hinge.
Doors are hung either right or left handed. If, when facing a door which opens towards you, the hinges are on the left-hand side, it is a "left-handed" door, and vice versa.
There is an endless variety in the patterns of butts with which doors may be hung. The best quality brass butts are now made with steel lining and spindle and steel-washered joints, a recent introduction being a butt with steel-washered ball-bearing joints, which ensure the easy swinging of heavy doors. Doors which are required to open over thick floor coverings and at the same time fit close to the floor when shut should have saddle boards; as shown on section in Fig. 91, fitted under them; or when the floor covering does not commence for some distance away from the closed position of the door, Rising Butts may be used for the same purpose. These are made with a spiral joint, which causes the door to rise while it is being opened, and to shut automatically. For positions where there is much traffic Swing Doors are usually provided. These may be either single or double doors, opening either way, and fitted with a spring hinge let into floor; or in cases where it is not desired to cut the floor there is a pattern which can be fixed above the floor.
"Helical spring butts" are a simple device for hanging a swing door, and can be provided with single or double action.
Borrowing an idea from the ancient Egyptians, doors are sometimes hung on top and bottom centres, or "Pintles." These, fixed at the middle of the top and bottom rails, cause the door to revolve, giving a passage on either side. This is known as a Butterfly Door.
Sometimes cases occur where doors opening into a room would cause obstruction and be inconvenient. "Sliding doors" are then if possible arranged. They may be made to slide along the face of the wall, but it is much better to have them slide into a covered chase in the wall, or partition, as in Fig. 131, if it can be managed. For this a running bar or track is required, supported at each end, and in the case of double doors in the middle also. This is usually rounded on the top, and carries hollow-edged friction rollers, which are contained in brackets attached to the top of the door. The bottoms of doors should also be provided with hollow-edged guide rollers, running on a guide fixed flush with the floor or metal tongue running in a groove. The doors may be made to open and close simultaneously by means of flexible wire cords running from one door to the other through pulleys at the ends; or rack bars may be fixed to each, and actuated by a pinion fixed to the centre support of running bar.