Windows may be divided into 3 classes - (1) casement windows (opening on hinges or pivots), (2) sash windows (opening by sliding up and down), and (3) skylights. The construction and arrangement of the woodwork of windows - their frames - will only be dealt with here, leaving the various methods of fixing the glass for discussion under Glazing.

When a window is to be inserted in a wooden structure, provision is made for fitting it to a portion of the framing of the building; but when the walls are of brick, a special frame must be made for the reception of the window. Fig. 677 shows a plan of the framing for a casement window 4 ft. high and 3 ft. wide. The side posts a, 4 in. by 3 in., are tenoned into the lintels, of the same dimensions, at top and bottom, and midway between them is the centre rail b, 4 in. by 2 in. The ends of the bottom lintel c are shown projecting into the walls d, and those of the upper lintel are extended in like manner; e is the interior window sill, a piece of 1-in. planed board, overhanging about 3/4 in.; f is the exterior sill, consisting of a piece of quartering 3 in. sq. sloped on the upperside and grooved on the under side, and nailed on beneath the lower lintel c. Fig. 678 shows the construction of the glass frame in its simplest form. The uprights a, b and crossbars c, d are "bevelled around their outer edge, and rebated for the reception of the glass on their inner edge; the crossbars are mortised into the uprights at the corners, and secured by pegs. Obviously the frame here shown is intended to carry only one pane of glass.

In larger frames, where it would be inconvenient to have the glass in one piece, the frame space must be divided by partitions, tenoned in as the original parts of the frame, and of the sectional shape indicated at e, f being the glass occupying the rebate. The glazed frame is hinged or pivoted to the main frame, and provided with a hook or rack for holding it open. The frames shut against stops on the main frame, which exclude wet.

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In sash windows, the glazed frames (called " sashes ") are made as before, but they are fixed in pairs, each occupying half the depth of the window. The construction of the outer frame admits of the sashes passing each other, by which the opening and shutting of the window are performed. When only one of the two sashes is movable, the window is called "single hung"; when both, "double hung." Each sash is hung independently, and, if movable, supported by counterweights or ends running over small pulleys. The top sash occupies the outer position and the bottom sash the inner. The outer frame, in which the sash-frames work, must always be made specially and fitted into the space in the wall. The construction of the outer frame is shown in Fig. 679. The sashes work on the face of the Calley-piecc a, separated by the parting-piece b, so that they may pass each other without touching. The counterweights c are similarly separated by the strip d; e is the front lining and f the back, joined by the end piece g; h is the top sash and i the bottom.

The manner of cutting the bottom bar of the upper frame, and the top bar of the lower one, so as to make a close joint, is shown in Fig. 680: a, top sash; b, bottom sash.

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The bars of sash-frames are generally more or less ornamentally moulded, and a bead is run round the outer frame.

A skylight is a sloping window fixed in a roof, part of which it replaces; that is to say, a portion of the ordinary roofing material, of any desired length, and of a width corresponding to the space between 2 or more rafters, is replaced by a glazed sash. In adjusting the sash to the space, the frame may be recessed to admit the rafters, or the rafters cut off to admit the frame. As both the roof and the skylight present a slanting position, most of the cutting is on the bevel. The space to be occupied by the skylight frame is enclosed by joining the rafters which are interfered with by cross-pieces of stout quartering. The whole structure is well illustrated in Fig. 6S1, taken from a practical article on the subject in Amateur Work : a is one of the raftersforming a side of the hole in the roof; b, c, pieces of quartering constituting the top and bottom, and secured to the rafters by the screws d whose heads are countemmk; e is one side of a rectangular box made of 1-in. planed deal, about 9 in. deep, dovetailed at the corners, and sloping as shown. This box should fit tightly into the rectangular space made for it, and be secured by nails or screws to the rafters at the sides and the crossbars b, c at top and bottom.

The top edge of this box should have a groove ploughed in it to carry off rain-water, and it may have a fillet 1/2 in. high nailed all round the outside, to form an enclosure for the sash that is to lie on the top. This sash / is made in the usual way, and, if not to be opened, is screwed down securely on the top of the box, which it fits exactly, dropping inside the fillet; but if it is intended to be opened the top edge only must be secured, and that by hinges joining it to the box. The sash is raised and lowered by the rod g, which may be of any reasonable length. When the sash is fixed and completed, the roofing material must be adjusted to it, to exclude the weather. But before laying the roofing (slates, tiles, felt, etc.) up to the skylight, pieces of sheet lead are spread all round it, one at the head h being turned up the woodwork of the skylight and slipped up under the slates k, another i at the foot lying over the slates k, and one on each side, similarly arranged for keeping out the wet. These strips of lead are nailed down in place before the roofing is secured over them. They should extend about 6 to 9 in. in each direction on the roof, besides the turn-up on all sides of the skylight.

The lead must be bent and fitted by the aid of a piece of planed hard wood, on which a hammer can be used. The joints may be soldered if desired, as described under Soldering. Angular fillets nailed all round at the base of the skylight reduce the sharpness of the bend in the sheet lead, and hence help to preserve it.

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