How Roof Trusses Are Set by Hand
- Staff Desk
- 36 minutes ago
- 8 min read
Building a roof begins long before shingles go on. One of the most important steps is setting the roof trusses, which create the main shape and strength of the roof. Many homeowners do not see this process up close, and it may seem complicated or even unsafe. But understanding the basics can help homeowners feel more comfortable with the work being done on their home.
This blog explains how roof trusses are set by hand, what tools and steps are involved, why proper support and bracing matter, and what makes the process safe and successful. Even though cranes are commonly used in construction today, there are times when trusses can be set manually, especially for smaller structures.
1. What Roof Trusses Are and Why They Matter
Roof trusses are the wooden frames that shape the roof. They form the main structure that supports the roof sheathing, shingles, and any snow or wind loads. They also help distribute weight safely to the walls below.
There are many truss types, such as:
Gable trusses, used at the ends of the roof
Standard trusses, used across most of the roof
Scissor trusses, which create a vaulted ceiling inside
Girder trusses, which carry extra weight and support other trusses
Every truss must be installed correctly to avoid roof problems later. Proper placement, spacing, bracing, and fastening are all essential for a strong roof.
2. Setting the First Gable Truss: How Everything Begins
The process usually begins with the gable truss, which sits at the end of the building. This truss is important because it helps guide the placement and alignment of all the others.
Before lifting the truss, builders add a nailer board on top of the wall. This board has two jobs:
Supporting the truss when it is set in place
Acting as a backing for drywall inside the home
Because walls can be long, a single board may not cover the entire length. Builders use a long 2×6 first and then cut smaller pieces to finish the ends. To position the nailer accurately, a 2×4 block is used as a spacer to create perfect alignment along the edge of the wall. Nails are placed every 16 inches to make sure the nailer holds firmly.
3. Safety Considerations When Setting Trusses
Roof work can be dangerous. While roofers often wear safety harnesses during shingling or similar tasks, starting a roof and lifting trusses can limit where harnesses can be attached. Because of this, workers rely on experience, careful movements, and strong temporary bracing to keep the trusses stable.
Two common types of braces used are:
Strongbacks (or Stiffbacks)
These boards catch the gable truss when it is lifted so it does not fall backward or forward. If the truss is tall, extra boards may be added to stiffen the support even more.
Kicker Boards
Placed on each side of the wall, these prevent the truss from sliding off the edges.
Careful marking is also important. A center mark is added on the nailer so the truss can be lined up perfectly when lifted.
4. Lifting the First Truss Into Place
Because the example roof is small, two people can lift the gable truss by hand. The truss is carried onto one side of the wall, then the other side is lifted onto the opposite wall. Once both bottom ends are resting on the walls, the truss is slowly pivoted upright.
A ladder or temporary support helps hold the truss in a standing position until it can be secured. Once in place, screws are added through the stiffback to keep the truss from moving. Nails or screws long enough to reach through the truss into the nailer board are then driven in to anchor the truss permanently.
5. Running a String Line for Straight, Even Trusses
To keep the roof perfectly straight, a string line is stretched across the tails of the trusses. This line acts like a guide, ensuring that each truss goes in the right place and stays in the same plane.
Builders often space the string line off the truss by about 1½ inches so they can measure accurately without the string being pushed outward. If the string line is off, even by a little, the entire roof can become crooked.
6. Marking Wall Plates for Proper Truss Spacing
Next, lines are marked on the top plates of the walls to show where each truss will sit. Many roof systems use a 24-inch on-center layout, meaning each truss is spaced two feet apart. This ensures the load is distributed correctly.
Every fourth stud often lines up with a truss. This alignment connects the truss through the wall framing all the way to the floor joists, creating a strong vertical load path.
7. Bracing the First Gable Truss
Normally, diagonal bracing would run from the gable truss down to the outside of the building. If the needed materials are not long enough, the builder may:
Set several trusses first
Add diagonal braces to the newly installed trusses
Brace this group of trusses to the floor to hold everything straight
This method keeps the structure solid and prevents any movement as more trusses are added.
8. Installing the First Standard Truss
Once the layout marks and string line are ready, the first standard truss can be lifted into place. Workers lift it upright, attach a brace across the top, and use the string line to set it correctly.
Understanding roof pitch is also important. A pitch like 4½:12 means that for every 12 inches horizontally, the roof rises 4½ inches vertically. Different pitches affect how easy or difficult truss installation can be.
9. Working Through the First Section of the Roof
After the first two or three trusses are set and braced, the installation becomes more efficient. The spacing remains consistent because of the layout marks. Bracing keeps the trusses from tipping over, which could cause damage or injury.
Bracing is especially important because, until the roof sheathing is installed, trusses can be unstable. Continuous bracing during installation keeps the roof safe.
10. Transitioning Back to Another Gable Truss
When reaching the opposite end of the roof section, another gable truss must be installed. Interior walls can be used to support and slide trusses into place. This makes lifting easier and keeps everything level.
The gable truss can be prepped on top of interior walls, which prevents workers from lifting a fully prepared truss up onto the exterior walls. Only the top half of the gable truss needs sheathing because the lower part will be covered by interior framing.
When cutting multiple angled pieces of sheathing, keeping the first scrap piece makes it easier to mark the same angle on later pieces.
11. Using the String Line on the Next Wall
Once the second gable truss is ready, the string line must be moved to the next section of wall. This allows the remaining trusses to follow the same straight line and continue the proper overhang.
12. Installing the Girder Truss
A girder truss is stronger than regular trusses and often made with a two-ply design. It has a larger bottom chord (such as a 2×6) to carry extra loads.
To install the girder:
The measurement of the truss that will connect into it is marked on the wall.
That mark determines exactly where the girder must be placed.
Screws are used instead of nails on the ends so adjustments can be made if needed.
After positioning, the girder is secured tightly.
Once aligned, the girder truss must be nailed thoroughly along both faces with alternating nails along the bottom chord. This makes it strong enough to support other trusses.
13. Installing Truss Hangers
Truss hangers (similar to joist hangers) must be placed where future trusses will connect into the girder. Each hanger is held flush with the bottom of the girder truss and nailed using short, strong hanger nails.
Because these nails are small and can be hard to grip, needle-nose pliers or a metal strap nailer make the job easier and safer. Once all hangers are installed, the system is ready for the intersecting trusses.
14. Setting Trusses for the Porch or Cantilevered Section
Some roofs include trusses that extend past the exterior wall to create a cover for a porch. These trusses are handled the same way, with careful measuring, bracing, and hangers set exactly where needed.
15. Building a Temporary Wall for Support
For trusses that will use hangers, it is helpful to build a temporary wall underneath. This wall can:
Hold the trusses while they are prepared
Support the trusses until they are set into the hangers
Be reused later as an interior wall inside the finished home
Repurposing the temporary wall saves time, money, and materials.
16. Setting a Gable Truss on Scaffolding
Setting a gable truss is easier and safer when it is built while lying flat on scaffolding. The overhang ladders (the small extensions forming the roof overhang) can be built at the same time. This keeps workers off ladders later and speeds up the job.
Once the gable truss is ready, it is lifted upright and braced securely. A block is placed on the tail so the string line can continue across all trusses with the correct overhang.
17. Installing Scissor Trusses
Scissor trusses have angled bottom chords that form a vaulted ceiling. When set into hangers, proper bracing keeps everything aligned. The temporary wall makes this easier and safer.
Once all scissor trusses are set and connected to the hangers, long braces run down to the floor or other stable points to lock them in place.
18. Tightening Gaps Between Trusses
Even with careful measuring, small gaps can appear between trusses. These gaps must be removed before the trusses are permanently secured.
To close the gaps:
Screws on the sides of the trusses are removed.
A sledgehammer is used to gently tap the girder truss into position.
New screws (often 5 inches long) are driven into each connecting truss.
This ensures the trusses sit tight and straight.
19. Toenailing and Final Securing
After the trusses are aligned and gaps removed, the girder truss is toenail-fastened on both sides. This locks everything in place so the roof framing remains solid.
20. Moving to the Garage Trusses
Before closing in the main living room area, garage trusses are installed. Scaffolding and braces are set up again to slide the trusses safely across the space. Once positioned, they are secured and checked for alignment with the string line. Gable trusses are prepared the same way as before.
21. Removing the Temporary Wall and Completing
the Structure
After all trusses are set and braced, the temporary wall used to support the scissor trusses can be removed. This wall can then be reused inside the home, such as dividing the kitchen and living room.
22. Final Bracing and Installing Hangers
The truss hangers must be fully nailed to secure the trusses tightly to the girder. Each hanger needs all required nails to prevent movement and ensure long-term strength.
23. Installing Sub-Fascia and Roof Sheathing
Once the trusses are completely set, straightened, and braced:
Sub-fascia boards are added along the roof edges
Roof sheathing is installed across the trusses
The sheathing locks the entire roof system together, creating a strong, stable base ready for underlayment and shingles.
24. The Benefits of Using a Crane (When Possible)
Even though this example shows how trusses can be set by hand, cranes make the process much easier. A crane can:
Lift trusses directly into place
Move roof sheathing onto the house instead of carrying it
Reduce labor time
Improve safety
Provide smoother, more accurate placement
For large homes or tall roofs, hiring a crane is strongly recommended.
25. Final Thoughts
Setting roof trusses is a careful and detailed process. Every step—from placing nailers to running string lines, from lifting trusses to adding braces—plays a key role in creating a safe, strong, and long-lasting roof.
While trusses can be set by hand on smaller projects, the process requires:
Accurate measurements
Solid bracing
Careful lifting
Strong fastening
Consistent alignment
Proper safety awareness
Understanding these steps helps homeowners appreciate the craftsmanship that goes into building a roof. Whether trusses are set by hand or with a crane, the goal is always the same: a straight, solid structure that will support the home for decades.