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tie to 50 degrees, then glue and screw
it to the rafters with 15⁄8-in. decking
screws [ 4 ]. For each of the two gable-
end trusses, cut a 2x4 collar tie to
56 in. long; miter-cut each end to 50
degrees. Set each collar tie in between
and f lush with the rafters, then screw
it in place with 2-in. decking screws.
To the rear gable-end truss, add
three small triangular 2x4 blocks.
Place one in each lower corner,
between the rafter and collar tie [ 5 ],
and one in the upper corner tucked
beneath the gusset plate. The blocks
create a rough opening for the oper-
able air vent. To the front gable-end
truss, install two 135⁄8-in.-long ver-
tical 2x4 blocks. Miter-cut the upper
ends of the blocks to 40 degrees, and
notch the bottom ends to fit snugly
over the 2x4 collar tie. These two
blocks provide fastening support for
the polycarbonate panels.
CUT AND ASSEMBLE THE
AIR VENT FRAME
Make the frame for the air vent from
six 1x3s. Cut the top 1x3 to 8¼ in.
687945long, and the bottom 1x3 to 36 3⁄8
in.; square-cut both ends of each
piece. Next, cut two short side parts
to 41⁄8 in. long, mitering their upper
ends to 40 degrees. Lastly, cut the two
angled parts to 171⁄8 in. long; miter
each end of both parts to 40 degrees.
Assemble the air vent parts, then
glue and screw a ½-in. plywood gus-
set plate across the top joints [ 6 ], and
across the joint at each lower corner,
with 1¼-in. decking screws.MAKE THE GREENHOUSE
DOOR
To ma k e t h e 2 4 5⁄16-in.-wide x 76¾-in.-
tall greenhouse door, start by cutting
two 1x3 vertical stiles to 76¾ in. long.
Next, cut the three horizontal rails
to 195⁄16 in. long; cut the head rail and
midrail from a 1x3, and cut the bot-
tom rail from a 1x4.
I joined the door frame parts
using a plate joiner to cut slots for
compressed-beech biscuit splines.
Position the top edge of the mid-
rail 37¼ in. down from the head rail.
After cutting corresponding slots in
the parts, I applied glue to the slots,
inserted the biscuits, and clamped
the frame together [ 7 ]. If you don’t
have a plate joiner, glue and screw
½-in. plywood gussets across the
joints with 1¼-in. decking screws.
Let the glue cure overnight.FRAME THE WALLS
All four walls of the greenhouse are
framed with 2x4s. Cut the horizontal
top plates and sole (bottom) plates for
the two sidewalls to 8 ft. long. For the
rear wall, cut the top and sole plates
to 65 in. Next, cut five 2x4 studs for
each sidewall, and four studs for the
rear wall, to 65¼ in. To assemble the
walls, drive two 3-in. decking screws
through the top and sole plates and
into each wall stud [ 8 ].
To frame the front wall, which
includes the doorway opening, you’ll
need ten 2x4 parts: Cut the sole plate
to 65 in. and then cut two double-2x4
top plates. Each double top plate con-
sists of an 185⁄8-in.-long 2x4 topped
with a 17¾-in.-long 2x4. Next, cut two
wall studs to 65¼ in. long, and two
trimmer studs to 75¾ in. (The trim-HOW TO BUILD A BACKYARD GREENHOUSE