|Ridge Pole and Rafters
With the front and
rear outer walls temporarily attached to the side walls with a
couple of screws or pipe clamps, cut a ridge board for the roof that
spans the distance between the front/rear walls. Position the ridge
board so that is centered at the peak and hold in place with a pipe
clamp (Figure 1). Now you can layout and cut the rafters.
To establish the top angle for the rafters, clamp a scrap piece
of 2x3 material to the inside of the outer wall and with a square
held against the ridge board, mark the cut line on the wood scrap
(Figure 2). Use the same approach to layout the bottom angle, this
time placing the square against the side wall. Also measure the
distance from the outside of the side wall to the top edge of the
ridge -- this represents the length of the top edge of the rafter.
It should be about 18" more or less.
With the rafter angles and length established, cut out the
rafters with your miter saw. I recommend first cutting the bottom
angle on all the rafters. Using one of these pieces as a template,
measure up from the cut end and mark the location of the top cut.
Then set the miter saw for the top angle and cut the template
slightly long. Gradually sneak up on the layout line until the
rafter fits snugly in place. (If you've done things correctly, the
top and bottom cut lines will form a right angle when a square is
placed against them). Finally, set a stop for your saw and cut the
rest of the end rafters to final length (total of 4).
Clamp the end rafters in place as shown in Figure 3 and screw the
top of each rafter to the ridge beam. You may want to drill a
countersink so as not to risk splitting the material. Also secure
each end rafter to the wall using 1-2 screws inserted from the outer
wall. These will hold the structure in place for the rest of the
assembly (the clamps would be in the way when the roof panels are
The two inner rafters are cut slightly shorter than the end
rafters because they butt up against the concealed fascia boards
that run along the base of the roof frame. These boards enhance the
structural integrity of the removable roof. With the end rafters
clamped in place, cut two fascia boards that span the distance
between the rafters. Position each fascia so that it rests against
the top of the side wall and is in the same plane as the rafters
(See the pics). Then measure the distance between the top edge of
the fascia and the ridge beam -- this will define the length of the
inner rafters. Mark and cut the inner rafters.
At this point, all of the roof framework should be cut to size.
Toe screw the end of each fascia into the end rafters. Do the same
for the inner rafters. A single screw at each joint will suffice for
now -- additional screws can be added later when the frame is
removed to install the insulation panels.
You'll notice in the photos that the inner rafters are not
actually in the middle of the roof. This is because I used two
pieces of plywood for one side of the roof and positioned the inner
rafter to line up with the point where the two pieces met. For the
sake of symmetry, I also offset the other inside rafter.
Roof Panels and Insulation
The next step is to create the two exterior roof panels. Each is
22" wide by 39" long, which allows for about 3" of overhang all
around. It's best if each panel is a single piece of plywood.
However, I ended up using two pieces for one side because I wanted
the grooves in the T1-11 plywood to all line up and run vertically,
and I didn't have enough large pieces left - with the proper groove
orientation - to use a single piece for each side. If you plan to
cover the roof with shingles, it should be much easier to find two
whole pieces of plywood since you won't care if the grooves line up
Alright, enough rambling... Do what you must to come up with two
roof panels of sufficient size. Rip each to rough width and cut to
finished length. The ends where the two panels meet at the peak of
the roof should be cut at an angle so the panels fit tightly
together. This angle is the same as the top angle of the roof
rafters. Transfer this angle to your table saw and cut two pieces of
scrap wood to see how they line up. Adjust as necessary and when the
angle is correct, go ahead and cut each roof panel.
Position the roof panels on top of the roof frame. When you're
satisfied that they meet tightly at the peak and overhang evenly on
the front/back, remove one of the panels and clamp the other in
place as shown in Figure 4. (It helps to have an assistant for this
operation). Then insert a few screws into the clamped panel to
attach it to the frame. Remove the clamp and attach the other roof
panel in a similar manner.
Now it's time to work on the interior roof panels. For these, I
used some 1/4" thick material that I found on the woodpile. Remove
one of the end walls as shown in Figure 5 and measure the distance
from the peak to the side wall, with the tape measure held against
the bottom edge of the roof rafter. This distance represents the
width of the interior panels. (Actually, one panel will be slightly
narrower than the other - by the width of the plywood - because it
will butt up against the other panel). Measure the panel length also
- it should be the same as the length of the side wall panels. Cut
the two panels to size and check their fit. Don't get too mental if
the panels are a little undersize - only the dog will ever see it.
Remove any screws securing the roof to the walls and with the
help of your able-bodied but underpaid assistant, pick up the roof
and place it upside down on the workbench. Cut out four pieces
of foam insulation panel to fit inside the roof frame and tape in
place (Figure 7). Then screw on the interior roof panels. This is
also a good time to insert additional screws to better attach the
outer roof panel to the frame. I recommend toe-screwing them from
the inside rather than putting holes into the top of the roof.
The last step is to attach a ridge cap. It not only enhances the
appearance of the house but helps to keep water from getting into
the roof panel joint and really stiffens up the roof structure. I
made a cap from 3/4" x 3-1/2" cedar with a piece of 6" wide flashing
underneath it (Figures 9-12). To reduce the opportunity for water to
get into the joint, I ripped one edge of each cap piece at a 16.5
degree angle (to match the pitch of the roof) and then put in 3-4
screws to attach the pieces to each other. The completed cap
is then screwed onto the roof with a half dozen screws or so.
Next: Front/Back Walls ->
Figure 1. Temporarily attaching ridge pole.
Figure 2. Laying out the top angle for the rafters.
Figure 3. Test fitting rafters.
Figure 4. Roof frame depicting end rafters, inner rafter, concealed
fascia, and ridge.
Figure 5. Close-up view of roof joint.
Figure 6. Side view of roof with front wall removed.
Figure 7. Underside of roof with insulation panels in place.
Figure 8. Close-up view of ridge beam and rafters.
Figure 9. Roof flashing.
Figure 10. Layout diagram of roof cap.
Figure 11. Ridge cap in place.