We will start at the outside corners, and from these points draw lines C G in Fig. 177 at forty-five degrees with the front and side wall lines of the wing, until they meet. The lines must meet exactly in the center of the wing between the two side wall lines, and from this point a line should be drawn at right angles to the front wall line of the wing, but away from this wall line instead of towards it. This line is marked E in Fig. 177. It will intersect the hip line G of the main roof and from this point of intersection a line F should be drawn at forty-five degrees, which will meet the side wall line of the wing in the point in which this side wall line meets the main wall of the building. One slope of the roof over the wing C, Fig. 175, will be the same as the slope of the end of the main hip roof, and so the lower part of the line C, starting at the point A, may be erased and the upper part only left to show as a hip line. The line F in this case also will be a valley line. Thus the wing C, Fig:175, will be completely roofed over and shown on the plan. Our roof plan is now complete in outline, all the lines marked E being ridges, all the lines marked G being hip lines, and all the lines marked F being valley lines. The same method of procedure may be followed out in the case of any roof plan, and the final complete plan obtained by successive steps as explained above. The first step is always to lay out the roof over the main portion of the building and then to proceed with the roofing of the projecting portions or wings.
Ridge. In the lean-to roof the rafters rest at the top against the wall of the building of which the ell, or porch, is a part; and the work of framing the roof consists simply in setting them up and securing them in place with spikes or nails. The pitch roof, how ever, is formed on the principle that two pieces which are inclined against each other will hold each other up, and so the rafters must rest against each other at the top in pairs, as shown in Fig. 178. It is customary to insert between the rafters, at the top, a piece of board about 1 inch in thickness and deep enough to receive the whole depth of the rafter, as shown at A in Fig. 1.79. This piece of board is called the ridge or the ridge pole and extends the whole length of the roof. It serves to keep the rafters from falling side ways, and keeps the roof frame in place until the roof boarding is on. It is sometimes extended above the rafters, and forms a center for some form of metal finish for the ridge, as shown in Fig. 180.
Interior Supports. In small roofs which have to cover only narrow buildings and in which the length of the rafters is short, there is no necessity for any interior support, and when the rafters have been cut to the correct length, set up against the ridge, and secured in place, the roof framing is complete. In long spans, how ever, the roof would sag in the middle if it were not strengthened in some way, so it is customary to support long rafters as near the center as possible. This support may be formed by placing a piece
of studding under each rafter, somewhere between the plate and the ridge, and if this is done very much lighter rafters can be used than would otherwise be considered safe. It is claimed by some that it is cheaper to do this than to use the heavy rafters. A more common method is to use fewer upright pieces and to place a horizontal piece A on the top of them, running the whole length of the building and supporting each rafter. This is shown in Fig. 181. An upright piece B should be placed under every sixth or enth rafter in order to give the necessary stiffness to the whole construction. For the uprights, pieces of ordinary studding 2X4 inches or 2X3 inches in size may be used. When there is to be a finished attic in the building, these upright studs may be made to form the side walls of, the attic rooms, and are then spaced about 16 inches on centers to receive the laths. Such walls are called dwarf walls.
Another form of interior support is the collar beam or tie beam. This is a piece of timber which extends between the rafters on opposite sides of the roof and ties them together, as shown at A in Fig. 1S2. It may be a piece of board about 1 inch thick and S or 10 inches wide, which is nailed onto the side of the rafter at each end. It is placed as near the center of the rafter as may be practicable, and in the case where a finished attic is required it forms the support for the ceiling. For this reason it must be at a considerable height from the attic floor, and can not always be placed very near the center of the rafter. The important point is to see that it is well nailed at each end.
Double Gable Roof. A very interesting form of gable roof is that in which there is a double gable with a valley between, which forms the roof of an ell when the main roof is a simple pitch roof. This form of roof is shown in Fig. 183. Fig. 1S4 shows how such a roof may be framed. The piece A is placed in the wall and supported by the studding so as to serve as a plate to receive the ends of the valley rafters B. These, together with the piece C, form the framing for the shallow valley between the two gables. The valley rafters on the outside, marked D in the figure, arc similar to those used in the case of a single gable. The pieces E E arc jack rafters and are very short. This form of roof is not common, but in some places it gives a good effect.
Gambrel Roof. A gambrel roof is framed in very much the same way as is a pitch roof or a hip roof. The slope of the roof, however, is broken at a point between the plate and the ridge. The part of the roof above this break makes an angle with the hori zontal plane of less than forty-five degrees usually, while the portion below the break makes an angle with the horizontal plane greater than forty-five degrees. This is shown in Fig. 1S5.