Transcript Unit 47 — Gable, Gambrel, and Shed Roofs

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Unit 47
Gable, Gambrel, and Shed Roofs
Gable Roofs • Gambrel Roofs •
Shed Roofs • Dormers
Unit 47 — Gable, Gambrel, and Shed Roofs
A gable roof slopes in only two directions.
Unit 47 — Gable, Gambrel, and Shed Roofs
Framework for a gable
roof includes ridge
board, common rafters,
and gable studs.
Unit 47 — Gable, Gambrel, and Shed Roofs
A bird’s mouth is formed
by the heel plumb cut line
and seat line.
Unit 47 — Gable, Gambrel, and Shed Roofs
When calculating true rise when there is a roof
overhang, the total rise and stand are first added. The
drop at the ridge is then subtracted.
Unit 47 — Gable, Gambrel, and Shed Roofs
The rafter table on a framing square can be used to
calculate rafter lengths for pitched roofs with 2 to 18
unit rises.
Unit 47 — Gable, Gambrel, and Shed Roofs
Common rafter length is
calculated by multiplying
the total run by the length
of the common rafter per
foot of run.
Unit 47 — Gable, Gambrel, and Shed Roofs
The actual length of a
common rafter is calculated
by deducting one-half the
ridge thickness perpendicular
to the plumb line.
Unit 47 — Gable, Gambrel, and Shed Roofs
A framing square is used
to lay out the plumb and
seat cuts.
Unit 47 — Gable, Gambrel, and Shed Roofs
A framing square or a
Speed® Square can be
used to lay out a common
rafter for a gable roof. The
roof in this example has
an 8 unit rise and a 10
overhang. The same
procedure is used
regardless of the layout
tool being used.
Unit 47 — Gable, Gambrel, and Shed Roofs
The step-off method combines
the procedure of laying out the
rafters with a procedure of
stepping off the length of the
rafter. In this example, the roof
has an 8 unit rise and a total
run of 5-9.
Unit 47 — Gable, Gambrel, and Shed Roofs
When constructing a
gable roof, common
rafters are precut and
then fastened to the
ridge board and wall
plates in a continuous
operation.
Unit 47 — Gable, Gambrel, and Shed Roofs
When ceiling joists
are spaced 16 OC
and rafters are
spaced 24 OC,
every other rafter
will tie into the
joists. Proper layout
ensures that rafters
and joists will tie
into each other
wherever possible.
Unit 47 — Gable, Gambrel, and Shed Roofs
Ridge board layout is copied from markings on wall
plates. Butt joints for ridge boards must occur at the
center of a rafter.
Unit 47 — Gable, Gambrel, and Shed Roofs
When only a few
carpenters are
present on a job
site to set the ridge
board, the ridge
board is secured in
position with props
and braces.
Unit 47 — Gable, Gambrel, and Shed Roofs
When several carpenters are present to raise a gable
roof, the method shown is used to set the ridge board
and nail rafters for a gable roof.
Unit 47 — Gable, Gambrel, and Shed Roofs
Many carpenters prefer
to cut the overhang after
rafters are fastened to
the ridge board and wall
plates. A chalk line is
snapped along the rafters
and a sliding T-bevel is
used to lay out the tail
plumb lines.
Unit 47 — Gable, Gambrel, and Shed Roofs
A gable end overhang can be framed with lookouts
and a fascia rafter. The fascia rafter is nailed to the
ridge board and fascia board. Blocking rests on the
end wall and is nailed between the fascia rafter and
the rafter next to it. An overhang is further
strengthened when the roof sheathing is nailed to it.
Unit 47 — Gable, Gambrel, and Shed Roofs
A gable end overhang can
be framed with a fascia
rafter supported by the
ridge board, outrigger, and
fascia board. Two common
rafters are placed directly
over the gable ends of the
building. The fascia rafters
are installed between the
ridge board and the fascia
boards. The gable studs
are notched to fit against
the rafter above.
Unit 47 — Gable, Gambrel, and Shed Roofs
Gable studs decrease in
length from the ridge
section toward the walls.
Unit 47 — Gable, Gambrel, and Shed Roofs
The lengths of gable studs can be
calculated with a framing square.
Unit 47 — Gable, Gambrel, and Shed Roofs
A framing square can be
used to find the angle of
the top cut on gable studs.
Combine the unit rise and
12 and mark the cut
along the unit rise side.
Unit 47 — Gable, Gambrel, and Shed Roofs
Gable studs provide
gable wall structure and
support rafters along
their bottom edges.
Unit 47 — Gable, Gambrel, and Shed Roofs
A gambrel roof is
essentially a gable roof
with a double slope on
each side. Note the walls
supporting the meeting
points of the upper and
lower rafters. The length of
the rafters for the lower
portion of the roof is based
on a 20 unit rise and a
4-6 run. The length of the
rafters for the upper
section is based on a 4
unit rise and an 8-0 run.
Unit 47 — Gable, Gambrel, and Shed Roofs
Common rafters for the
upper and lower portion
of a gambrel roof are laid
out differently. The cuts
laid out in this illustration
are based on the unit
rises and runs shown in
Figure 47-23.
Unit 47 — Gable, Gambrel, and Shed Roofs
When constructing a
gambrel roof, the lower
portion of the roof is
constructed first. If the attic
space is to be used for a
living area, the subfloor
should be installed before
the roof is constructed.
Unit 47 — Gable, Gambrel, and Shed Roofs
A shed roof has common rafters with overhangs at
each end.
Unit 47 — Gable, Gambrel, and Shed Roofs
When laying out
common rafters for
a shed roof, the
length of common
rafters is based on
the unit rise and
total run of the roof.
Unit 47 — Gable, Gambrel, and Shed Roofs
The construction of a gable
dormer is similar to that of a
gable intersecting roof. A
gable dormer has a level
ridge board.
Unit 47 — Gable, Gambrel, and Shed Roofs
The front wall of a shed
dormer is usually directly
over the exterior wall
below. The rafters extend
from the main ridge
board. The rafters must
be pitched enough to
shed water and snow.