In Fig. 82 is shown the left side elevation of the roof, in which A B represents the length of the plate line. C D F, the starting points of the hips and valleys, and C and F the points of the main hips.

Fig. 82.   Left Side Elevation of Roof.

Fig. 82. - Left Side Elevation of Roof.

Fig. 83.   Rear Elevation of Roof.

Fig. 83. - Rear Elevation of Roof.

From C and F set off the run of the main common rafter, as C D and F O. From O and D set off the length of main common rafter, as shown by the dotted lines O P and D G. Connect G and P for the main ridge. Draw G C and P F for length and position of main hips. Set off the length of the common rafter on the front gable A J and draw the ridge line J K. Set off the length of common rafter on the rear gable B H and draw the ridge line H I. Now from the center of the left gable set off the length of the common rafter, as shown by the dotted line L M. Connect M and D for length and position of valley rafter on the front side of the left gable. F I will be the length of the valley on the rear gable. M Pis the length of the broken hip which stops against the ridge of the left gable at M, and G K is the length of the broken hip which stops against the ridge of the front gable at K. The jacks are cut from the ridge line H I to the rear gable valley F I ; also from the broken hip M P to the valley M D and from the broken hip G K and ridge line K J to the plate line A D. The length of the common rafter on the left gable is shown by F E. This completes the left side elevation and shows the length of every hip, valley and jack, as viewed from this side of the roof. The next diagram, Fig. 83, shows the rear elevation of the roof ; A B represents the length of the plate line, C D E the starting points of hips and valleys, and C E the starting points of the main hips. Set off the run of the main common rafter, as E F, and draw the length of the common rafter perpendicular, as shown by dotted line F P. Draw P E and P C for the length and position of the main hips. Set off the length of the common rafter on the left gable, A J, and draw the ridge line J K. Set off the length of the common rafter on the right gable B H, and draw the ridge line H I. From the center of the rear gable set off the length of the common rafter, as shown by the dotted line L M. Connect M and D for the rear gable valley. E G shows the length of the common rafter on the rear gable ; I E is the right gable valley. The broken hip P K stops against the ridge of the left gable at K, and the broken hip P M stops at the ridge of the rear gable at M. The jacks are cut from the ridge line H I to the valley E I and from the broken hips M P and P K to the rear gable valley M D. This completes the rear elevation and shows the length of every rafter as viewed from this side of the roof. It will be noticed in Fig. 83 that the right gable appears to the left hand in the diagram and the left gable to the right. This is due to the fact that as we view the front elevation of the roof, Fig. 80, we call the gables right and left. Now, if we view the roof from the rear, the right gable will be to our left and the left to our right, as shown in Fig. 83.

An Important Point

Fig. 84.   Roof Having Three Gables of the same Pitch, the Front Gable being Narrower than the other Two.

Fig. 84. - Roof Having Three Gables of the same Pitch, the Front Gable being Narrower than the other Two.

For the purpose of illustrating an important point in roof framing we will refer to Fig. 84, which represents the plan of a roof having three gables of the same pitch, but the front gable being narrower than the other two. Let A B C D E F G H represent the wall plate and from A set off the run of the common rafter to I ; square up the rise to J, and connect A and J for the length of the common rafter on the main part of the roof. Swing the common rafter around to a perpendicular position, as shown by A K on the left gable. Set off the length of the common rafter on the right gable F L, and connect K with L for the ridge line. Next, set off the run of the common rafter on the front gable E M ; square up the rise M N, and draw E N for the length of the common rafter. From M set off the length of the common rafter perpendicular to O and then draw the valley from E through the point O, continuing it to the ridge, which is the nearest place of support in a self-supporting roof. It is a common practice among mechanics to stop both valley rafters at O, but this leaves the valleys without support and as a consequence the roof sags and gets out of shape even before the carpenter has it finished. This is noticeable on large roofs, where, to secure the greatest strength in the framing of the roof, it is necessary to run the first valley rafter to the ridge, as shown by E P, and butt the second valley rafter against the first, as shown by B O. E P is the length of the valley rafter which joins the ridge and the bevel at P is the bevel across the back of the same. B O is the length of left valley rafter and cuts square across the back.

The jacks are cut from the ridge to the valleys, as shown. A bevel set in the angle where they join the valley will give the bevel across the back. The plumb cut is the same as that of the common rafter shown at J. To find the plumb cut of the valleys set off the run of the common rafter on the front gable A B, Fig. 85; now, at right angles to A B set off the run of common rafter from B to C, and draw A C for the run of the valley. From C square up the rise of valley to D and draw D A, which will give the length of the left valley the same as B O in Fig.

84. The bevel at D, Fig. 85, is the plumb cut and at A the bottom cut. The plumb cut of the valley E P is the same as the extension of the rafter to the ridge line and does not change the cuts.