by Mike Guertin
Several years ago, while discussing how to lift trusses for
a hip roof, our crane operator suggested that I preassemble
some of the components on the ground. I decided to give it a
try, so I worked a little late that day, attaching the jack
trusses to the girder trusses (see Figure 1). The lift went off
without a hitch. On the next hip roof house I built, I went
further with the preassembly and attached the hip trusses and
corner jacks while the assembly was still on the ground. Even
factoring in some extra time for head scratching, the method
saved us time.
1. The girder truss (or hip girder) is the
backbone of the hip roof truss assembly; most roofs
require a double girder truss. Attached to the girder
truss at right angles are the jack trusses (sometimes
called the face jacks or end jacks). Extending at a
45-degree angle from the girder truss to the corners
are the hip trusses (also called hip jacks, king
trusses, or corner jacks). The short trusses that
attach to the hip trusses are the corner jacks (also
known, confusingly, as hip jacks or side
Nowadays, on a single-story house, I usually just attach the
jack trusses to the girder trusses before the crane lifts the
assembly, since the rest of the components are easy to install
in place. But on a two-story house, it's more efficient and
safer to assemble as much as possible on the ground. These days
I even sheathe the hip system before lifting (see
"Installing Hip Roof
Laying Out the Girder
I begin by squaring up and marking out one of the girder
trusses while it's still lying flat on the pile of trusses.
Trusses are sometimes fabricated out of dimension, especially
at the tails, so when I lay out the jacks, I don't measure from
the tails of the girder truss. Instead, I establish a line
perpendicular to the top chord of the girder truss, in order to
establish reference points for laying out the locations of the
jack trusses (Figure 2).
2. To establish a 90-degree angle down from the
girder truss's top chord as a reference, first mark the
midpoint of the top chord (a). Then pull two tape
measures from the top corners of the truss, crossing
the tapes at the bottom edge of the chord (b). Adjust
the tapes from side to side until they register the
same measurement and mark that point as the midpoint of
the bottom chord. The two midpoints can then be used as
reference points for laying out the locations of the
jack trusses (c).
Generally, roof trusses are spaced 2 feet on-center, but one
of the spaces between jacks will usually be less than the
typical 22 1/2 inches.
Jack trusses and hip trusses sit in hangers attached to the
girder truss. Once I've marked the jack locations, I install
the hangers, initially using only two 1 1/2-inch nails per
hanger. Later, when the second girder truss is paired with the
first, I'll finish nailing the hangers with 10d or 16d spikes
that grab both girders.
To support the diagonal hip truss and the adjacent jack
truss, several styles of hangers are available. I usually use a
universal hanger that will fit either the left or the right hip
trusses (Figure 3).
3. This universal hanger supports both the hip
truss and one of the jack trusses. This type of hanger
is reversible and can be used on either the left or the
While the girder truss is still on the pile of trusses, I
nail a single jack truss roughly in the middle of the girder.
Then I roll the girder upright and carry it to a flat location,
accessible to the crane, to continue the assembly (Figure 4).
The area doesn’t need to be level, as long as it’s
4. A single jack truss nailed to the girder
truss will hold it upright while the rest of the jack
trusses are installed.