Adding Timber Rafter Tails To a Stick-Framed Roof -
A Really Big Beam
The rafter-tail assemblies at the garage and entry were larger
and more complicated. For one thing, they included a concealed
gutter (Figure 6). They also required large carrying beams (42
feet long, in the case of the garage overhang) resting on
massive knee brackets. These giant assemblies were fabricated
and put together in the shop, then shipped to the site for
Figure 6.The overhangs at the garage doors rest on
massive knee brackets and include a hidden gutter, lined with
the same metal used on the standing-seam roof.
I inquired about ordering a single-piece 42-foot-long beam, but
it would have taken three months and was too expensive.
Instead, I joined two shorter lengths together, end-to-end,
using a traditional pegged scarf joint made permanent with
two-part epoxy (Figure 7).
Figure 7.To make a 42-foot-long carrying beam, the
author joined two pieces with a locking scarf joint, using the
same router template to cut the identical profiles (top). The
two pieces are forced tightly together by a pair of opposing
wedges at the joint's center (bottom). While such lap joints
are strong even when assembled dry, the author applied two-part
epoxy to prevent water entry and further increase the joint's
Without epoxy, this method can also be used to make a strong
joint that can be taken apart. The joint requires only one
router pattern to make both interlocking ends, and the pattern
ensures an exact fit the first time, every time.
A pair of wedges driven against each other in a pocket provided
at the joint's center force the interlocks tightly
To make the blanks for the knee brackets, we used stepped
lengths cut from a single beam and reversed every other piece
end-for-end for epoxy glue-up. This reverses the direction of
the growth rings and helps ensure that if one piece wants to
twist in one direction as it dries, the piece next to it will
likely be twisting in the opposite direction, so they cancel
each other out (Figure 8). The final blanks measured about 30
by 60 inches and weighed about 150 pounds each, too heavy to
manhandle through a band saw. Instead, I made a single-sided
MDF router template to contour the brackets and worked the
stock from both sides to complete the shaping.
Figure 8.The giant knee brackets were cut out of
large slabs, glued up from lengths of fir 6x8. The author used
pieces cut from the same long beam and reversed the growth
rings of every other one to cancel out the tendency of the wood
to warp and cup.
Installation. To help position the knees in the proper attitude
on the wall, I made a set of guide blocks that would be tacked
to the wall to define the necessary vertical and horizontal
offsets. We used a man-lift to help raise and hold the brackets
in place while we drilled and blind-bolted them from inside the
wall, using 5/8-inch by 12-inch lag bolts passed through the
wall framing (Figure 9). Once the brackets were installed, we
lowered the main assembly in place with the lift and bolted it
down (Figure 10).
Figure 9.After wrestling the knee bracket into
place on temporary supports (top), one carpenter stabilized it
(middle) while the other attached it with lag screws through
the framing inside (bottom).
Figure 10.Resting on shop dollies, the 42-foot beam
and rafter-tail assembly awaited transport to the site (top).
On site, the heavy lifting was done by a material handler as a
carpenter guided the assembly into place on the knee brackets
(middle and bottom).
The whole process — for both the entry and garage
overhangs — took two men a couple of hours to complete.
The framing crew followed up with the soffit planking, making
it ready for the metal roofer.
Mike Randowns Narragansett Housewrights in