Wood 167Headers and Trimmers. Headers and trimmers are
required for any openings (such as chimneys) just as in floor
and ceiling joists. For a complete discussion of headers and
trimmers, refer to Section 13–3, “Floor Framing.”
Collar Ties. Collar ties are used to keep the rafters from
spreading (Figure 13.50). Most codes and specifications
require them to be a maximum of 5 feet apart or every third
rafter, whichever is less. A check of the contract documents
will determine the following:
a. Required size (usually 1 6 or 2 4)
b. Spacing
c.Location (how high up)FIGURE 13.50.Collar Tie and Ridge Board.Determine the number of collar ties required by dividing
the total length of the building (used to determine the
number of rafters) by the spacing, and add one to close up
the last space.
The length required can be a little harder to determine.
Most specifications do not spell out the exact location of the
collar ties (up high near ridge, low closer to joists, halfway
in between), but the typical installation has the collar ties
about one-third down from the ridge with a length of 5 to 8
feet, depending on the slope and span of the particular
installation.EXAMPLE 13-22 COLLAR TIES
From Figure 13.51, collars are 8longUse 14 collars39 > 3 13 spaces39 rafter pairs78 rafter pairs without gable end overhang Purchase QuantitySize Length (lf ) Pieces2 48 14FIGURE 13.51.Collar Length. Ridge. Theridge board(Figure 13.50) is taken off next.
The contract documents must be checked for the size of the
ridge board required. Quite often, no mention of ridge
board size is made anywhere on the contract documents.
This will have to be checked with the architect/engineer (or
whoever has authority for the work). Generally, the ridge is
1 inch thick and one size wider than the rafter. In this case,
a 2 8 rafter would be used with a 1 10 ridge board. At
other times, a 2-inch thickness may be required.
The length of the ridge board required will be the length
of the building plus any side overhang.