Build the trusses now because the empty floor will be part of your temporary truss jig. Plus the floor makes a nice clean work space to cut and organize the pieces on..
Figure 3.4, Finished truss comparison
Take a look at the finished truss so you can see what it looks like and know where all the pieces go.
Decide if you want to use a 3/12, 6/12 or a 12/12 pitch.
See Figure 3.2, Truss jig and Table 5, Truss dimensions
On the long side of the floor choose the plywood joint closest to the center. This will be the centerline of your truss jig. Measure up this line a distance of “G”, which represents the height of the truss. Mark this intersection.
Take a 2×4 upper top plate and cut it to length “A”. This sets the width of the truss. Mark the center of this 2×4 and attach it to the edge of the floor matching the above truss center line.
Extend it above the floor 1 1/2 inches and secure to the edge of the floor with several 3 inch screws. This board simulates the top plates where all the trusses will eventually rest.
Attach stops
See Figure 3.1, Truss dimensions. Cut 2 truss rafters with Rafter angle “J” on one end and length “H” plus a few inches. Bring the angled ends together at the intersection of the height and centerline mark on the floor, and bring the lower edges firm to the corners of the simulated top plate.
When these boards are in position lay 2- 2×4 stops as per figure 3.2 and attach them to the floor with 3 inch screws.
See Figure 3.7-3.8, Angle Template
Print Figure 3.7 or 3.8 out and lay a cut 2×4 on top to verify that your upper rafter angle “J” is correct for 3/12 or 6/12 pitch trusses only.
12/12 roof pitch is easy because it’s a 45 degree angle.
Set overhang distance: Your custom dimension “H”
At this point you will decide how much overhang you want on your shed. Length dimension “H” in Table 5 is an estimate that will give you between 10 and 12 inches of overhang.
Pull a tape and measure the actual overhang, then add the width of the truss end board on either end to get the final overhang dimension. Experiment with length of these 2 rafter boards until you are satisfied with the overhang. This is your custom dimension “H”.
Cut truss base template
Secure these 2 truss pieces to the floor with 3 inch screws so they don’t move around. Lay a board across the bottom of these rafter pieces at the simulated top plate. Take a short 2×4 and lay it on top and in line with the rafter pieces. Mark the intersection on either end and cut these angles on both ends.
This will be your template to cut the rest of the truss base pieces. Don’t worry if it’s off a little because the OSB truss webbing will hide the joint and provide strength.
Uprights
These trusses are designed so you can add a 48 inch wide loft along the center. Space the edge of the uprights 24 1/2 inches from the center. Cut the top angle, determine the length and fit into place.
Put a 2×4 stop at the upper ends and a 2×4 stop on either side of the lower ends and screw to the floor.
See figure 3.3, 14 and 16 wide trusses
2 Uprights are sufficient for 8, 10 and 12 wide trusses. But for 14 and 16 wide trusses you will want to add another brace.
See Table 3, Calculate number of pieces to cut
See table 3 for the truss count. Take the number under the column of the center spacing (16 O.C. or 24 O.C.) you want to use. The materials list is base on building with 16 inch centers.
This number plus 2 (for the flying trusses) is your truss count number.
The truss count number less 3 times 14 ( (count-3) x 14=total ) is the number of osb web pieces you’ll need to cut.
Take the same truss count number times 2 for the number of 2×4 rafter pieces you’ll need to cut.
The truss count minus 2 is the number of horizontal base pieces you’ll need.
Cut truss pieces
Use this first sample truss as a template to measure and cut all your truss pieces.
Cut OSB web pieces
Lay a 12×12 piece of OSB on top of each joint and mark it for maximum coverage of the joint. Cut the first one for each joint and use it as a template to cut the rest of the pieces.
3 Different trusses
You will need 3 different types of trusses:
- Regular trusses with OSB webing on both sides
- Gable end trusses with OSB webing on one side only. The other side will have the siding attached.
- Flying end trusses with temporary OSB webing and bottom brace. These temporary pieces will be removed after they are attached in place.
Assemble flying trusses
The first 2 trusses will be flying trusses used on the gable end overhang. They will be attached to the flying rafters and truss end boards. The temporary braces are necessary to make construction and placement easier.
Lay 2 truss rafter pieces in place and secure to the floor with 3 inch screws. Attach the OSB webbing to the top joint with several screws. Do not use nails or construction adhesive because this webbing will be removed after installation.
Lay a 2×4 brace near the bottom of the rafter pieces and secure with several 3 inch screws. This is to keep the bottom of the rafter pieces spaced correctly.
Assemble regular trusses
Lay 2 truss pieces in the jig and secure to the floor with 3 inch screws. Attach the OSB webbing to each joint. You can use nails or screws and add construction adhesive for a strong joint.
Remove the screws holding the rafter pieces, flip the truss over and attach the OSB webbing to the other side of the joints.
Do this for all but the last 2 trusses.
See Figure 3.5, Assemble gable end trusses
The gable end trusses don’t need the uprights for strength. Rather, they need uprights spaced properly to nail the siding to.
Layout the simulated top plate with marks 16 inch on center. Cut and install uprights at these center marks and secure with OSB webbing on one side only.
Sheet gable end trusses
Remove the screws holding the truss rafters to the floor, flip it over and put it back in place aligned with the simulated to plate.
Lay the first piece of siding on the truss assembly and allow 2 inches of overhang below the bottom of the simulated top plate. Nail in place then attach the rest of the siding in place.
Trim the top edge of the siding to match the truss.
See Figure 6.1, Cut for flying rafters
Stand the truss upright and mark for the flying rafters. These 2×4 rafters will provide strength for the gable end overhang.
The first one should be about 2 ft from the top (center) of the truss and the other about 4 ft from the truss end. You will want to add a third spaced between these 2 on each side for 14 and 16 ft trusses.
Use a 2×4 scrap and mark on either side for the width. Mark the front or back down 1 1/2 inches for depth.
Set the depth of your skill saw at 1 1/2 inches and several cuts to remove as much wood as possible. Then use a chisel to finish the cut so the 2×4 lays in properly.
Build the second gable end.