Fig. 65. A brace.
Consider a building 20 feet broad and 6 inches above one-third pitch. The half of 20 feet equals 10 feet, or 120 inches. Seven feet 2 inches (86 inches) is the height of the peak above the plate. It is quickly seen that this problem, like the other, can be solved in more than one way. If the long end of the square is laid on at 20 inches and the short end at 14¹⁄₃ inches, and this is repeated six times, both the bevels and the length will be secured ([Fig. 64]), for 6 multiplied by 20 equals 120 inches, half the width of the building, and 6 multiplied by 14¹⁄₃ equals 86 inches, the height of the peak. Or the long end of the square might be laid on at 24 and the short end at 15¹⁄₅ five times, but squares are not marked in fifths of inches, hence the previous method would be best.[5] The same results would be reached by laying the square on at 15 and 10³⁄₄ inches; eight steps would then be required instead of six. The longer and fewer the steps within the limits of the square, the better.
[5] Since the square is laid on, see [Figs. 61], [62], in the same manner as for cutting a stair; each one of these spaces is called a “step.”
If it is desired to cut a brace 3 × 4 feet run, 3 steps, using the lengths 12 and 16, will give both the length of the brace and the bevels ([Fig. 65]). Take a rafter which has a projection requiring a notch to be cut in the lower side, and the same rule will apply. The line A, [Fig. 66], is horizontal and the face of the plate is perpendicular; therefore, the line B must be at right angles to A. The only thing now to be determined is how deep the notch shall be, for it is evident that if the line A represents the long end of the square and B the short end of the square, the notch will fit the plate.
Fig. 66. Adjusting to the plate.
Fig. 67. The rafter.
Fig. 68. The rafter trimmed on the outer end.
That part of the rafter which extends over the building may be reduced in size, but usually it is well to leave it entire (as in [Fig. 67]) if the house is large. If the lower end of the rafter should appear too heavy, it may be treated as in [Fig. 68]. The bevels at the ends of the rafters are the same as at A and B ([Fig. 66]).
The outlines of a story-and-a-half house, which form is most undesirable for various reasons, are shown in [Fig. 69]. The chambers cannot be well lighted or aired. The outlines of the room interfere with the placing of furniture, and such chambers are far more uncomfortable in warm weather than are those in two-story houses. It will be seen that the collar-beam, C, must be placed so far above the foot of the rafters in order to get a fair height of ceiling, that it has little binding power, and that the building cannot be tied together at the plates in the center, since the tie would interfere with the door in the cross wall. It will also be seen that the second-story joists are so far below the plates that their power to hold the building together is small. Many of the one-and-a-half-story houses have “sway-backed” peaks because of this faulty construction. (See [Fig. 35], page 124, broken-back house.) If story-and-a-half houses must be built, then they should be covered by roofs having at least one-half pitch, in which case the collar-beams could be placed relatively lower and the thrust on the plates would be very much diminished by the steeper roof ([Fig. 70]). One-, two-, three- or more storied houses are easily and certainly prevented from spreading since one tier of joists always coincides with the foot of the rafters, to which they can be securely fastened. Fortunately, the story-and-a-half house is less constructed than formerly.
