Truss Me: A Beginner’s Guide
Welcome to “Truss Me On This”, the blog from Fargo Truss Systems. We're kicking things off with the basics, because it's easy to forget that most people who hire a builder or contractor have never actually thought about what's holding their roof up.
So if you've looked at an unfinished roof and wondered what that triangle-shaped wooden frame is doing up there, read on.
What Is A Roof Truss?
A roof truss is a pre-built framework, usually wood, that supports a roof and carries its weight down to the exterior walls. It's basically the skeleton of the roof: a repeating pattern of triangles engineered to hold weight without buckling.
Most trusses are built in a shop, not on the job site. Ours are manufactured in a controlled environment and then trucked out ready to install. That's a big reason trusses replaced site-built framing as the standard for most homes and commercial buildings.
Why Triangles?
There's no trick to it. Triangles are just the most structurally efficient shape there is. A rectangle can rack and collapse under pressure, but a triangle pushes force along its sides instead of letting the shape distort. String a bunch of triangles together the right way and you get a structure that can carry a lot of weight relative to how much material went into it.
The Parts Of A Truss
A few terms come up constantly, and once you know them, trusses stop looking like a random tangle of wood.
Top chords are the two outer members that form the sloped top of the truss, similar to rafters. The bottom chord is the horizontal member at the base, which often doubles as a ceiling joist. Webs are the interior pieces running between the top and bottom chords, and they're what create all those smaller triangles. Connector plates are the metal plates at each joint holding everything together and spreading out the stress.
That's really it. Four parts, and you can read almost any truss on any job site.
Trusses vs. Framing It By Hand
Before engineered trusses were common, crews framed roofs rafter by rafter, on-site, one piece at a time. It worked, but it was slow and left a lot of room for inconsistency from one crew or one day to the next.
Trusses solved most of that. Because they're built in a factory, every truss on an order matches the last one exactly. They go up fast, sometimes in a day what used to take a week of framing. They can also span longer distances without needing load-bearing walls in the middle of a floor plan, which gives building designers more room to work with. And every truss is engineered up front for the loads it actually needs to carry.
Why The Engineering Behind It Matters
Not every truss is built for the same conditions, and this is where it's worth paying attention to who's designing yours. A truss needs to account for the weight of the roofing material, expected snow load, wind exposure, and how the rest of the building is laid out.
A truss designed for a mild climate isn't automatically fine somewhere that sees heavy snow loads for months at a time. Getting the engineering right before the truss is ever built is a lot cheaper than dealing with problems after the roof is closed up.
A Few Common Truss Types
There are dozens of truss designs out there, but most jobs come down to a handful of them.
The Fink truss has that classic W-shaped web pattern and is probably the most common design for residential roofs, mostly because it's efficient and cost-effective. Queen post trusses are simpler and tend to show up on shorter spans, garages, and smaller structures. Scissor trusses slope the bottom chord along with the top, which creates that vaulted or cathedral ceiling look. Attic trusses leave extra open space in the middle so the attic can actually be used for storage or living space.
The point isn't to memorize all of them. It's to understand that the shape isn't arbitrary. Each one solves a different structural or architectural problem, which is why the cheapest option and the right option aren't always the same thing.
Why Any Of This Matters To You
You don't need to become a structural engineer to build or buy a house. But knowing roughly how a truss works means you can ask better questions, whether you're a contractor bidding a job, a developer planning a multi-unit project, or a homeowner trying to keep up with what your builder is telling you. It also helps you tell the difference between a truss package that was actually engineered for your project and one that's just lumber nailed into a triangle shape.
At Fargo Truss Systems, we design and build trusses for projects across the region, from single-family homes to larger commercial jobs, with the actual conditions of this region factored in rather than just the minimum the building code requirements.
What's Next
We'll get into the more technical stuff in future posts, including how to read a truss engineering drawing, what actually drives truss pricing, warning signs that trusses were installed wrong, and how snow and wind loads get factored into the design.
If there's something specific you'd like us to cover, let us know. We're happy to write about it.