Figure 2-25.-Setting up and bracing a ridgeboard when only a few workers are available.
called collar ties (fig. 2-23). In a finished attic, the ties
may also function as ceiling joists.
To find the line length of a collar tie, divide the
amount of drop of the tie in inches by the unit of rise of
the common rafter. This will equal one-half the length
of the tie in feet. Double the result for the actual length.
The formula is as follows: Drop in inches times 2,
divided by unit or rise, equals the length in feet.
The length of the collar tie depends on whether the
drop is measured to the top or bottom edge of the collar
tie (fig. 2-23). The tie must fit the slope of the roof. To
obtain this angle, use the framing square. Hold the unit
of run and the unit of rise of the common rafter. Mark
and cut on the unit of run side (fig. 2-24).
METHODS OF RIDGE BOARD ASSEM-
BLY. Several different methods exist for setting up
the ridgeboard and attaching the rafters to it. When only
a few Builders are present, the most convenient
procedure is to set the ridgeboard to its required height
(total rise) and hold it in place with temporary vertical
props (fig. 2-25). The rafters can then be nailed to the
ridgeboard and the top wall plates.
Plywood panels should be laid on top of the ceiling
joists where the framing will take place. The panels
provide safe and comfortable footing. They also provide
a place to put tools and materials.
Common rafter overhang can be laid out and cut
before the rafters are set in place. However, many
Builders prefer to cut the overhang after the rafters are
fastened to the ridgeboard and wall plates. A line is
snapped from one end of the building to the other, and
the tail plumb line is marked with a sliding T-bevel, also
called a bevel square. These procedures are shown in
figure 2-26. The rafters are then cut with a circular saw.
Figure 2-26.-Snapping a line and marking plumb cuts for a