It is often desirable to use hand-split shakes for the roof covering.
These are usually made from cedar, but may be of any straight-grained
wood, free from knots, which splits easily. First, the logs are cut in
lengths of 30 to 36 inches and then the shakes are split off with a tool
called a froe (fig. 20).
After the log cuts are set on end, the froe is held on the upper end of
the block and then struck a blow with a wooden maul which causes a piece
of the block or shake to split off. Being hand-split, the thickness
varies somewhat; the minimum is 1/2 inch. A roof of thin shingles,
lacking sufficient scale, is never as effective as a rough textured one,
using 3/4- to 1-1/4-inch thick shakes, to harmonize with the sturdy
appearance of the log walls. The width, normally 6 to 8 inches, is
governed by the size of the blocks of wood and varies accordingly, while
the length is governed by the spacing of the roof logs or purlins. Shakes
are always laid on the purlins in single courses, lapping the sides 1-1/2
to 2 inches and over-lapping the ends at least 6 inches, as illustrated
in figure 19. Nailing is usually done with six- or eight-penny galvanized
box nails. Copper nails may be used for greater permanence. A good shake
roof will not leak although from the inside of the building it may appear
to have many holes.
The ordinary, uninteresting, straight-line effect at the butts may
be broken up by staggering them from 1 to 2 inches, as is often done
with shingles. This method produces an effect more in keeping with the
log walls. Although involving greater care and additional labor it is
preferable, from an architectural point of view, to the more common
custom of laying them to uniformly straight lines.
At the ridge of the roof, where the shingles or shakes intersect,
provisions must be made for weatherproofing. The shingled Boston ridge,
comb intersection, or pole ridge, shown in figure 21 are practical and
much more satisfactory from the standpoint of architectural effect than
stock metal ridges, ridge boards, and other methods.
[Illustration: Figure 21.--Ridge treatments.]