This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
It is often desirable to separate the lights of a window, whether it is a double-hung window or one of the casement type, by means of a horizontal division called a "transom." In this case the additional light which comes above the transom is in the nature of an extension to the window proper, and it is usually hung in a different way, sometimes being made stationary so as not to be allowed to open at all. Fig. 328 shows a double-hung window with a transom and a transom sash. A is the transom, B is the transom light, C is the upper sash of the window proper, D the lower sash, and E is the meeting rail. In Fig. 329 is shown a casement window with a transom, A being the transom, D the transom light, CC the two lights of the window proper which are hinged at the sides, and D the meeting stile. As no description of the meeting stile for casement windows has yet been given, a section through the stile is shown in Fig. 330. The bead at A A may be omitted if desired and the stiles may be made plain. This, of course, cheapens the construction somewhat.
Fig. 328. Elevation of Double-Hung Window with Transom.
A transom for a double-hung window must combine two members, namely, a headpiece for the window proper, and a sill for the transom sash to stop against. These properties determine the construction of the transom. In Fig. 331 is shown a section taken vertically through the transom of a double-hung window, and it will be seen that the two members have been provided for. A is the sill for the transom sash, which is shown at C, while B is the head jamb for the main window frame, the upper sash being shown at 0. The piece D is in line with the outside casing of the window at the jambs, and E is the stop bead which is in line with the stop bead at the sides. The space marked II is filled with blocking. G is the window stool on the inside and F is the finished face of the transom on the inside.
In Fig. 332 is shown a section taken vertically through the transom of a casement sash such as is shown in Fig. 329. It will be seen that this transom differs somewhat from the transom shown in Fig. 331, the head for the casement frame being quite different from the head for a double-hung window frame.
Fig. 329. Casement Window with Transom.
In this figure, A is the top rail of the lower part of the window, that is, of the casement sash itself, while D is the bottom rail of the transom sash which forms the upper part of the window. At H is shown a small groove in the top rail, which is intended to catch any water which may be driven through the opening between the sash and the frame during heavy rains. This groove should be deeper at one end of the top rail than it is at the other end, so that the water will flow away toward the side and be carried down to the sill, which will throw it outward. E is the stop bead immediately inside of the casement sash. B is the piece which forms the head of the casement frame, and is the same in outline as the pieces which form the jambs. On top of the piece B is the sill C of the transom frame, and the two are placed close together so as to form really one solid transom. The sill piece is made with a wash on top, the slope of which should be about 2 inches to the foot, and on top of the sill piece comes the lower rail of the transom sash D. The piece F is a stop bead carried across the frame on the inside just above the sill piece for the transom sash to stop against in case it is hinged at the top to swing outward, or to receive the hinges in case it is hinged at the bottom to swing inward. The latter arrangement is the most common one. The piece G forms the inside finish of the transom bar and may be treated in any way desired.
Fig. 330. Section through Casement Meeting Stiles.
Fig. 331. Vertical Section through Transom of Double-Hung Window.
Fig. 332. Section through Transom of Casement Window.