52 March/April 2022
INSTALL THE TRUSSES
Add the roof trusses by tilting the
rear gable-end truss into place on
top of the rear wall [ 17 ]. A lign the
truss f lush with the outer edge of the
wall, and drive a 3-in. decking screw
up through the top plate and into
the bird’s-mouth cut in each rafter.
Then install the three intermedi-
ate trusses, making sure to position
each over a wall stud [ 18 ]. Fasten each
intermediate truss as you did the
gable-end truss: Screw up through
the top plate at a slight angle and into
the bird’s-mouth cut [ 19 ].
Set the front gable-end truss on
top of the front wall and tilt it into
place [ 20 ]. Drive 3-in. drywall screws
up through the top plate and into each
rafter, and then secure the truss with
two 3-in. metal L-brackets. Screw the
brackets to the top of the trimmer
studs and into the 2x4 collar tie [ 21 ].SHEATHE THE ROOF
Before attaching the polycarbonate
roof panels, set a 1x2 strap into the
notches cut into the top edge of each
rafter. Secure the straps by driving a
single 15⁄8-in. decking screw throughthe 1x2 and into each rafter [ 22 ].
Then install a 2x4 block between
each pair of rafters [ 23 ] to close off
the space between the top plate and
the underside of the polycarbonate
roof panels.
Fasten the polycarbonate panels
to the rafters with 1¼-in. decking
screws, spaced 16 in. apart [ 24 ]. Con-
tinue installing the panels across the
rafters on each side of the roof, leav-
ing a 1⁄8-in. gap between each panel.
Once all the roof panels are in
place, make the ridge cap, using a
pressure-treated 1x8 and 1x10, each1718 1920 2122232425HOW TO BUILD A BACKYARD GREENHOUSE
PHOTOGRAPH/ILLUSTRATION BY TEEKAY NAME