Fig. 17 - Plan of Gable Roof.
Figs. 18, 19 and 20. - Side and End Elevations of a Gable Roof.
The gable roof is the most common in use, and is formed by two sets of rafters which meet at the . ridge. Fig. 17 shows a plan of this kind of roof, Fig. 18 a side elevation, Fig. 19 an end elevation and Fig. 20 showing the size of roof necessary to cover the side elevation represented in Fig. 18. An error liable to occur in taking roof measurements from architectural plans consists in taking the line A B in the side elevation, Fig 18, for the length of the rafter. This line is only the perpendicular rise of the roof, as shown in the end elevation, Fig. 19, by the dotted line A B, In Fig. 19, B C represents the length of rafter which, when shown in a perpendicular position, is indicated by B C in Fig. 20. This shows the length of roof and of rafter necessary to cover the side elevation, represented in Fig. 18. Hence the area of the roof is found by multiplying the length of the roof by the length of the common rafter, which gives the area of one side. This amount doubled will give the area of both sides.