In the '60s and '70s, California tract builders were all
gang-cutting their rafters. Since then, trusses have taken over
in that market, and production cutting has become a dying art.
Yet in many areas, carpenters continue to stick-frame roofs,
and it's surprising how many of them cut rafters one piece at a
time. Unlike most carpenters who gang-cut rafters, I did not
learn this technique on the West Coast. About 20 years ago I
got a job working for a builder on Cape Cod and he
production-cut all his roofs. I eventually moved back to
eastern Pennsylvania and became a framing contractor, where I
continue to gang-cut my roofs.
It doesn't matter whether there are 20 or 200 rafters to cut:
It's always faster to gang them together and cut them all at
once. When I frame a roof, the actual cutting time for the
rafters is usually less than 15 minutes. This doesn't include
layout or stacking the lumber on racks, but I'd be laying out
the cuts and stacking the material on sawhorses anyway. To help
with the heavy work, we use an all-terrain forklift. Once the
rafters are cut, we lift them to the roof all at once.
The first thing we do is build a set of temporary racks. They
don't have to be elaborate, just sturdy and stable. I take a
couple of 2x10s or 2x12s and brace the ends so they won't roll
over (see Figure 1). It takes less than a minute to build a set
of racks. We build them low because they're more stable that
way and it's a comfortable height to cut from. It's easier if
you put the racks on a level surface, but they don't have to be
perfectly level. The racks can run slightly up or down hill.
The important thing is for the top edges to be in the same
Figure 1.The rafters are supported by a pair of
simple racks and are kept upright by the triangular blocks at
The racks are usually about 14 feet long, but I'll make them
longer if there are a lot of rafters to cut. Long racks can get
kind of shaky under a heavy load of lumber, so if there are
enough rafters I'll put a third rack under the middle of the
Racking. Putting the lumber
on the racks is called racking. To save time, I rack the entire
roof package at once. This includes commons plus hip and valley
jacks. It doesn't matter if the rafters are more than one
length; they can still be in the same rack. One rack should be
within a foot or so of the head cut and the other should be
under the seat cut. If there are enough different lengths, we
may build an intermediate rack to support one end of the
shorter pieces. We could use a different set of racks for the
shorter rafters, but there isn't always space to do it and it
would require us to lay out an extra set of cuts. It's usually
easier to do everything at once.
Since the birdsmouth is on the bottom of the rafter, we rack
them with the crown side down. It's very important to stack the
rafters tight; I use a hammer to beat them together. If the
rafters are exposed, we'll use a piece of scrap to protect them
from dents. We nail blocks to both ends of the racks to keep
the rafters together. The blocks are shorter than the rafters
so they won't interfere with the saw.
Laying Out the Cuts
As with any roof-cutting project, there's a certain amount of
prep work involved. I figure out all the cuts at home the night
before I cut the roof. That way I don't waste time on the job
or get distracted and make a mistake that ruins a whole pile of
lumber. The last thing I want is to tell a builder to order 100
more 2x10s because I cut all the rafters 9 inches short.
However you figure the lengths, you have to put the cut lines
on the bottom of the rafters. It's like working upside down, so
it takes some getting used to. I mark the head cuts, seat cuts,
and tail cuts on the two outside rafters and use a chalk line
to transfer the marks to the rafters in between (Figure 2). I
mark the head first, then determine rafter length and the seat
cut from there.
Figure 2.Layout is done on the outer pieces (top),
and a chalk line is used to transfer the cut lines to the
pieces in between (bottom).
Rafters of more than one length and for more than one roof
pitch can be stacked in the same rack. I use 12-inch spacer
blocks to separate different groups of rafters on the rack
(Figure 3). This speeds the process because it allows us to
fill the racks and get more cutting done in each setup. This
also allows us to make the same cuts on one end but different
cuts on the others.
Figure 3.Twelve-inch spacer blocks separate groups
of rafters on the racks so that different cuts can be made,
increasing the efficiency of both the stacking and cutting
The idea behind this method is to run the saw through all the
rafters in a single pass. We do the head cuts first, the tail
cuts second, and the birdsmouths third. Circular saws do not
have the depth of cut to gang-cut the heads and tails. Instead,
we use an adjustable table attachment on a chainsaw to make the
long straight cuts (Figure 4).
Figure 4.A chainsaw has enough depth of cut to cut
heads and tails in a single pass. This saw is attached to a
custom-made shoe; an off-the-shelf model is available from Big
We always make the head cuts first. That way we can recut them
if the angle is a little bit off. A 2x4 nailed to the top of
the rafters makes a good fence for the saw. We usually cut the
tails before doing the seat and heel cuts because there's
nowhere to nail the fence if the birdsmouths are already
We use a slow, smooth cutting action and let the saw do the
work. The table should be held tight to the top of the rafters.
If one side of the table comes off the work, the pitch will be
wrong and there will be gaps where the rafter hits the ridge. A
good coating of silicone spray on all chains, blades, and
tables reduces friction and keeps blades sharper longer.