The common method of constructing the window frames in wooden buildings is shown by horizontal and vertical sections in Fig. 94. Such frames are frequently called skeleton frames in distinction from the box frames used in brick and stone buildings. The essential parts of such a frame are the pulley stile, A, the parting strip, E, the outside casing, B, the stop bead, S, and the head and sill. A band moulding, C, sometimes called the "outside architrave," is also necessary if the casing is flush with the boarding, but where it sets outside of the boarding the moulding is often omitted. The inside casing or trim, D, is a part of the inside finish, and not usually considered as a part of the frame. Very frequently, in cheap work, the tongue on the outer edge of the pulley stile, at R, is omitted and the casing, B, simply nailed to the pulley stile. This tongue, however, is a very important feature, as it prevents the pulley stile from warping or springing, and permits the sash to slide more freely.
The construction shown in Fig. 94 may be considered as the very cheapest, and is not recommended for good work.
In all first-class dwellings the sill should be made of the shape shown in Fig. 95; that is, with a rebate at K for the bottom rail of the sash to shut against, and a ground casing, G C, should be nailed to the inside edge of the pulley stile. It is not common, however, for builders to include these two features unless they are specified. The ground casing stiffens the pulley stile and keeps it straight, and gives a better nailing for the finish. If 1 ¾ inch sash are to be used, as is desirable in first-class work, and the studding is 4 inches wide, the outside casing should be placed outside of the boarding, so as to give a wider pulley stile. This also gives room for a strip, S, to which the guide for the fly screen, F, may be fastened. When there are to be outside blinds, with swivel slats, and also outside fly screens, some such arrangement as this is almost necessary. If the inside finish is to be of hard wood, the ground casing should be rebated for a thin strip, V, which should be put in after the plastering is dry. With the outside casing set outside the boarding the band mould or architrave is not really necessary, unless 3/8-inch shingles are used on the walls, but it relieves the plainness of the frame, and is generally used on good work.
In frames made as in Fig. 95, it is also desirable to hang a " pendulum " or thin partition between the weights to prevent their interfering in passing up and down. This pendulum is made of a stirp of 1-inch pine, as shown in Fig. 98, and is hung from the top so that it may be swung to one side for getting at both weights through one pocket. In all double hung window frames a piece about 18 inches high and 2 ¼ inches wide, with beveled ends, should he cut out of the lower part of the pulley stile to give access to the weights. This piece is called the " pocket," and is held in place by a screw at the lower end, and by a brad, or dove-tailed arrangement, at the upper end.
Fig. 96 shows a section through the head and sill of a still more elaborate frame. The sill has an additional rebate under the sash, with the idea of preventing the lower sash from getting " stuck," and also of keeping out rain and snow. This rebate is seldom seen, however, except, perhaps, in a few localities. The rebate at N is intended to form a stop for the bottom of the blinds, and is a desirable feature. This detail shows a heavy outside architrave, the inner edge being flush with the blinds and forming a rebate for them to shut into. This construction gives a very neat finish to the window. This detail also shows a different arrangement of the window stool, which is dropped \ an inch below the top of the sill and the stop bead carried across the sill. This makes a neat finish, but does not give as wide a stool as the construction shown in Figs. 94 and 95. If the finish is to be painted the sill is brought flush with the inside of the ground casing, and the piece V is omitted. With hard wood finish the stop bead and the piece V are made of the same wood as the finish. In first-class buildings the stop bead should be fastened with round headed screws, which may be of any desired finish ; in common work they are fastened with small finish nails,
Thicknesses. - All parts of the window frame except the sill and yoke are commonly made of 7/8-inch stuff. For large windows the pulley stiles should be 1 1/8 inches thick, and if no strip is inserted between the outer sash and the casing, the latter should also be 1 1/8 inches thick. In wooden buildings the sill should always be at least 1¾ inches thick. Sometimes a sub-sill is placed under the regular sill, but this is not common, and in ordinary construction has no advantage. The parting strip, E, is usually made 3/8 of an inch thick for 1 3/8 -inch sash, and 1/2 inch thick for 1 ¾ or 2¼-inchsash. The yoke is made from 7/8 inch to 1¾ inches thick, according to the custom of the locality. A thickness of 1 1/8 inches is just as good as 1 ¾ inches. The stool moulding is generally made 7/8 inch thick in moderate priced houses in the Eastern States, but in the West 7/8-inch boards are very seldom thicker than ¾ of an inch when dressed, and 1 1/8-inch stools are used there altogether. The depth of the weight box should be 2 inches for 1 3/8-inch sash of moderate size; for plate glass windows, and large windows with double strength glass, the minimum depth should be 2 ¼- inches.