Installing Floor Trusses – Tips, Tricks, and Order of Operations
Proper floor truss installation is essential for creating a strong, stable, and long-lasting floor system. Whether you’re new to truss installation or have years of experience, taking the time to understand the entire process can save you time, reduce errors, and improve the quality of your build. This guide covers everything you need to know, from verifying plans and preparing the site to laying out, spacing, fastening, and bracing your trusses. With the right preparation and techniques, you can ensure your floor system is safe, efficient, and built to perform.
Verification Before Installation
Verifying Plans
A truss placement diagram and truss drawing will be included in your truss package. You will want to verify that these documents match the blueprints and site conditions. It is uncommon for them not to match, but in the off chance there is a discrepancy, call your truss manufacturer to remedy the issue before the product is on site.
Once your product arrives on site, you will need to check that everything on the material list was dropped off by the truss delivery driver. The hardware provided will be notated on the materials list and individual trusses will be labeled to match the builder’s layout. In the unlikely event that materials are missing, contact your truss manufacturer immediately so they can bring out anything still needed.
Truss Placement Diagram
Truss Drawing
Delivery and Truck Space
Truss delivery equipment is often the largest that shows up to a job site during a build. A tractor and trailer combination with a boom truck requires a 24-foot by 24-foot level, sturdy spot to set up for offloading. It is best to deliver the floor trusses when you need them so they can be set down close to where they will be installed. In situations where this is not possible, floor trusses should be stored on dunnage or stickers to keep them flat and off the ground.
Tools Needed
Floor trusses are installed using common framing tools like hammers and nail guns. These trusses are typically light enough for two people to move by hand, but a forklift and boom truck can also be helpful. Once set in place, there is little danger of toppling due to the 3-and-a-half-inch flange on the top and bottom of the truss.
Truss Spacing and Layout
Standard Spacing
The spacing for your structure will be specified on the plans, on the truss placement diagram and on the truss design drawing. Common spacings for floor truss systems are 12 inches on center, 16 inches on center, 19.2 inches on center and 24 inches on center. This terminology indicates measurement from the center of one truss to the center of the next. These spacings are commonly used because they align well with 8-foot-long subfloor sheets, minimizing waste and cutting.
Laying Out the Trusses
The first truss you place on the exterior wall starts at zero, so it doesn’t follow the typical “on center” spacing. From there, you’ll measure to the center of the next truss based on your layout. All following trusses follow the “on center” layout. This method ensures the floor sheathing ends halfway over a joist, so the next sheet of sheathing can start on the same joist.
The plans will show which side of the structure to place the first truss. If this notation is ignored, potential conflict with plumbing or other obstructions may arise. If a plumbing drop is not accounted for, it could require restructuring bathrooms or conducting repairs on the trusses.
Occasionally, the most efficient way to lay a truss system may result in a plumbing drop conflicting with a truss. In this circumstance, your truss manufacturer can supply an additional truss off center on either side of the plumbing drop to resolve the conflict. It is not an issue if known about before the trusses are delivered.
Commonly, it may be called out for a truss to align with a wall. This truss may not match the layout of the rest of the floor system, but it is important to place it correctly. This truss may be supporting a wall above it, transferring load through the floor system or accounting for earthquake and wind resistance.
Truss Alignment
Wall Alignment
Your truss manufacturer will do their best to build every truss perfectly vertical with the correct span. Expert floor truss installers have recommended aligning the outside of the wall with whatever the outermost part of the truss is to ensure there is no part extending past the outside of the wall.
Top and Bottom Orientation
Floor trusses are built with camber in them, which is like an arch. This ensures that when all the loads are applied to the truss they will deflect just enough to end up flat. It is important that the trusses are built with the right way facing up to receive forces in the correct direction to transmit them to the bearings. If the truss is upside down, the lumber grades, plate sizes and webbing pattern may not be appropriate for the load.
Right and Left Orientation
Your truss placement diagram will have markers to note which end of the truss should be on which side of the building. At Truss Components of WA, we use triangles for this marking. This becomes especially important when the structure includes additional bearing points beyond the exterior walls. The truss will have special structural accommodation for those loads that could end up in open space when oriented incorrectly.
Additionally, these trusses are often designed with ribbon notches. The ribbon could end up on the inside instead of the outside if it is oriented incorrectly, causing difficulty down the road when it is time to tie the trusses together.
Bracing and Fastening
Strong Back Bracing
The recommendation of the Structural Building Components Association is to have a strong back brace every 10 feet. The strong back brace is a wood member, possibly a 2x6, that is fastened on the bottom or top of an upright member in the floor truss. Running through the whole truss system, bracing prevents toppling and ties the floor together to transfer weight uniformly.
Pre-Loading and Marking
Builders can pre-load the bracing into their floor trusses by sliding the bracing through the trusses before setting them in place. This method is especially important when building for the first floor above a basement. These floors are usually hung on the concrete foundation with sill plates. If a builder were to wait until the trusses were in place, the concrete foundation would limit the ability to load the bracing.
Your truss placement diagram indicates where each truss and brace should end up. Before placing the trusses, it is recommended to mark the wall plates and the bracing with a line and an x where each truss will be fastened. It is easier to nail down the trusses when you have a consistent layout marked throughout the structure. This method ensures that trusses stay straight across the depth of the building.
Fastening Techniques
When spreading out the trusses, it is recommended to spread three or four at a time and fasten them to prevent toppling. Different bearing conditions lend themselves to different fastening techniques.
The most common fastening technique is a ribbon notch. The truss will be notched at the top where it sits on the exterior wall. Builders will nail the truss to the bearing and nail a 2x4 member into the notches of floor trusses across the wall.
The builder is recommended to use sliding truss clips in cases where a non-load bearing wall is in the center of the structure. A sliding truss clip allows the truss to be fastened to the top of the wall to allow movement for loads applied.
When the top chord of the floor truss is directly adjacent to the bearing, builders can drive nails directly into the bearing from the top and bottom, anchoring the truss firmly in place. If the middle of the truss is adjacent to the top of the bearing, the same nailing method can be applied to ensure stability. Bearings occasionally have metal hangers installed before the floor trusses are installed. Once the floor truss is set into these hangers, it’s automatically held securely in position.
Order of Operations
Truss installation must happen in the proper order for the best outcome. Before the truss delivery, the builder should mark the walls using the placement diagram. Once the trusses arrive, they should be stacked close to where they will be installed. Next, the builder should mark the bracing where the trusses will go and pre-load the bracing into the trusses. Trusses are then spread out and braced three or four at a time. Once the floor system is completely fastened, the sheathing can be installed on top.
At the end, builders should nail the strong back bracing to the trusses from beneath. This method is safer than standing on the trusses and causing them to potentially topple or missing a step and going through the floor. Beyond safety, attaching the bracing from the top could unintentionally lock in deflection and cause the trusses to remain permanently bowed or uneven, even after the floor is completed.
Conclusion
Installing floor trusses correctly is more than just following a layout. It requires careful verification of plans and materials, thoughtful placement and alignment, and secure fastening and bracing. Each step plays a role in ensuring the trusses work together as a complete system that can support the structure above. By following a clear order of operations and prioritizing both accuracy and safety, builders can create a reliable and level floor that’s ready for the next phase of construction. With attention to detail and the right approach, a well-installed truss system will deliver lasting performance and peace of mind.
Ready to get started on your next project?
If you have questions about your floor truss layout, need help reviewing your plans, or want a quote, reach out to our team at Truss Components of WA. We're here to support you with expert advice, reliable materials, and the guidance you need for a smooth and successful installation. Contact us today and let’s build something great together.
