battens can be wedged in from the wall, or forced together by using a piece of quartering as a lever.
Floor Brads.
Nails used in flooring are called floor brads (Fig. 374), and they are driven through the floor-boards into the joists, two at each passing, about 1 in. from the edge.
Fig. 376.—Straight Floor Joint.
Fig. 377.—Rebated Floor Joint.
Fig. 378.—Rebated and Filleted Joint.
Fig. 379.—Rebated, Grooved and Tongued Joint for Secret Nailing.
Fig. 380.—Iron Tongue Joint.
Fig. 381.—Dowelled Floor Joint.
Joints for Floor-Boards.
Heading Joints.—The points of contact between the ends of two floor-boards are called heading joints (Fig. 375). A (Fig. 375) shows the section of a butt heading joint, but slightly less simple than the splayed heading joint shown in section by B (Fig. 375). These joints should always be arranged to occur over a joist, and in floors laid with the aid of a cramp, contiguous boards should have their heading joints on different joists—that is, should break joint. The actual joint is made in different ways. In common floors the boards simply butt up against each other A (Fig. 375); in better work the heading joints are splayed b (Fig. 375). Even with plain headings it is usual slightly to undercut the ends so as to present as close a surface joint as possible. Sometimes the heading joints are grooved and tongued in a similar fashion to the longitudinal joints described below. In very expensive work the ends of the boards are cut into a series of sharp, salient and re-entering notches, whose ridges are parallel to the surface of the floor. These notches fit one another, and form a tight joint. Such joints are sometimes used in oak floors; they are extremely troublesome and expensive to make, and the point nearest the surface of the floor is very liable to break away even in hard wood.
Edge Joints.—The ordinary straight joint for the longitudinal edges of floor-boards is shown in section by Fig. 376; the rebated joint (Fig. 377) is another common method, a joint requiring more work being the rebated and filleted (Fig. 378). The rebated, grooved, and tongued joint (Fig. 379) is useful for secret nailing. The joint shown in Fig. 380 has an iron tongue, and Fig. 381 shows the dowelled joint. The ploughed and cross-tongued joint with slip feather (Fig. 260, p. 62) is also used. In all floors which are ceiled underneath, means should be taken to prevent dust or particles of any kind from falling between the boards. Any accumulation of organic matter on the upper surfaces of the plaster is certain to decompose. The ceiling being, moreover, always more or less porous, these particles gradually work their way to the under surface, and produce a stained appearance, which no amount of whitewashing or scraping will remove. The usual method of preventing this is to form a ploughed and tongued floor. Each board is grooved on each edge, and thin slips, or tongues, either of wood or of galvanised iron, are then inserted (see Figs. 260 and 380). If of iron, the tongue should be galvanised. The tongue should
