Truss Designer vs. Engineer: Who Does What?
Most building projects involve an architect and an engineer of record (EOR). If you’re planning a project that involves roof or floor trusses, you’re also going to need both a truss designer and a truss engineer. These two roles are often confused, even by experienced contractors, but they serve very different purposes. One isn’t more important than the other, they just focus on different parts of the process. Here’s how they work together to get your trusses designed, approved and built.
The Truss Designer: Building for Efficiency
A truss designer is the first person who will work on your truss package after the architect and engineer of record finish their plans. This person works for the manufacturer and is focused on building a product that can actually be made in a truss plant. They take the design criteria provided by the project team and input it into design software to create a full set of truss drawings.
These drawings include the layout, the type of trusses, the shape of the trusses, the member sizes (like 2x4s or 2x6s), and all the connector plates. The goal is to create something that meets the project’s structural needs, fits the building's aesthetic, and can be manufactured efficiently. It’s important to understand that the truss designer is not responsible for legal compliance or engineering sign-off. They don’t stamp the drawings. That’s where the engineer comes in.
The Engineer: The Code Authority
While the truss designer focuses on what’s buildable, the engineer focuses on what’s allowed. A licensed engineer, either a PE (Professional Engineer) or an SE (Structural Engineer), reviews the drawings created by the truss designer to make sure they meet local building codes and structural requirements.
This includes checking the trusses for snow loads, wind speeds, dead loads from materials like HVAC systems and live loads that vary depending on how the space is used. For example, a commercial corridor has different load requirements than a guest room or a deck. The engineer ensures the trusses hold up under all these loads and that they work together as a full system. While the truss designer looks at each truss individually, the engineer zooms out to look at the entire truss system as part of the building.
More Than One Engineer
On most projects, there’s more than one engineer involved. The engineer of record is responsible for the structural design of the overall building. A second engineer is responsible for reviewing and sealing the truss package. These roles are different, but both are essential. One sets the design criteria. The other confirms that the manufactured trusses meet it.
The Process: From Design Criteria to Job Site
Here’s how it all comes together. The architect and the engineer of record set the project’s design criteria. This includes the aesthetics, like pitch and profile, and the structural needs, like load transfer and span requirements. This information is passed to the truss designer in the form of blueprints or load specs.
The truss designer uses this information to generate a truss layout. That layout includes every truss profile, web pattern, connector plate and chord size. Once the truss drawings are complete, they’re sent to the truss engineer. The truss engineer checks that every truss meets the structural needs of the loads input by the designer. If the design passes inspection, the truss engineer stamps the drawings, taking legal responsibility for the structural integrity of the trusses as long as they’re built exactly as drawn. That stamp is the green light for the manufacturing team to begin building the trusses.
A Simple Example
Let’s say you’re building a structure that requires a 30-foot truss span. The architect calls for a 6:12 pitch to match the building design. The engineer specifies a 25-pound snow load, a 7-pound top chord dead load and an 8-pound bottom chord dead load. The wind speed is 100 mph and the site is classified as Exposure C.
Those numbers may sound like a lot, but to a truss designer, they’re just inputs. Based on the span and loads, the designer decides to use a Fink-style truss, which looks like a W inside the triangle. They specify 2x4 top and bottom chords, vertical and diagonal webs to distribute the loads, and connector plates for each joint. The drawing is sent to the truss engineer, who confirms that this design can handle the loads. Once the truss engineer stamps the drawing, the truss gets scheduled for manufacturing and is eventually delivered to the job site.
One System, Three Roles
Here’s the bottom line. The EOR sets the requirements; the truss designer fits the components into those requirements and the manufacturer builds the trusses based on those approved plans. The result is a truss system that can be built efficiently, meets code and arrives ready to install.
When you work with a truss manufacturer, you’re not just getting material. You’re getting a process that includes both a designer and an engineer. Even if you never speak to the engineer directly, their seal of approval is what guarantees that your trusses meet code and are safe for the job site.
Understanding this process makes your entire build smoother. And when questions come up about who’s responsible for what, now you know exactly how these roles work together to get the job done right.
