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.
Fig. 250 shows the method of framing a church spire, or other high tapering tower. The base of the drum N is square and is supported by the posts A, one at. each corner, which rest on the sills B. The sills are supported by the roof trusses of the main roof. The corner posts extend the full height of the drum and are strongly braced in all four faces, with intermediate vertical studding C between them to form the framework for these faces. The spire itself may rest on top of this square drum or there may be another eight- or twelve-sided drum constructed on the top of the first drum, on which the spire may rest. This depends upon the design of the spire. The hip rafters D do not rest directly on top of the drum, however, as this arrangement would not give sufficient anchorage for the spire. They are made so as to pass close inside the plate E at the top of the drum and are securely bolted to this plate with strong bolts. This is shown at L, which is a plan of the top of the drum, showing the hip rafters in place. The plate is shown at E, and the hip rafters at D. The rafters extend down into the body of the drum as far as the girts II (shown in the elevation) to which they are again securely spiked or bolted, being cut out at the foot so as to fit against the girt. In this way a strong anchorage for the spire is obtained.
Fig. 250. Section Showing Contraction of Church Spire.
Horizontal pieces I are cut in between the hip rafters at intervals throughout the height of the spire, braces K, halved together at the center where they cross each other, are firmly nailed to the rafters at each end. These braces are needed only in lofty spires, which are likely to be exposed to high winds. At the top the hip rafters bear against a post M, the same as in the other towers. If a conical spire is called for in the design, the horizontal pieces I must be cut to the shape of segments of circles, and in this case the rafters are no longer hip rafters. The horizontal pieces I will receive the boarding, which will form a smooth conical surface.
The spire above the drum is usually framed on the ground before being raised to its final position. It then may be raised part way and supported by temporary staging while the top is finished and painted, after which it may be placed in position on the top of the drum.