The 8 Accessory Trusses Every Builder Wishes They Knew About Sooner
When you think about roof or floor trusses, your mind probably jumps to the main structural components. But there’s a whole category of trusses that don’t always make the blueprints but can make a massive difference on site. Accessory trusses are like the hidden support crew—offering smoother transitions, cleaner finishes, and serious time savings for framers. Here’s how they work and why they matter.
Slammer Truss: For Clean Transitions at Roof Intersections
The slammer truss is a simple but smart solution for when a lower roof ties into a wall or a taller roof. Typically, framers would add two-by material on-site to bridge the transition. But instead of that extra work, your truss manufacturer can build a Slammer: a dedicated truss that sits right at the transition point. It lets you carry both your roof sheathing and ceiling on the same plane. It's ideal when you're dealing with a roof-to-wall connection or two low-pitch roofs meeting. If it's just one roof tying into another truss and the ceiling continues uninterrupted, a single two-by might do the job. But if it’s happening in a couple of spots, adding a slammer is a no-brainer.
Sheetrock Backer: Support Where Layout Leaves Off
Sometimes, the ceiling layout doesn’t line up with your truss spacing. This is especially common when you have scissor trusses for a vaulted ceiling that flattens out in the back of the room. Your sheetrockers are left hanging with no place to tie into. That’s where a sheetrock backer comes in. This off-layout truss gives them a place to attach material and cleanly transition the ceiling. Whether on an interior or exterior wall, it eliminates the guesswork and patch jobs in finishing.
Fur Down Truss: Quick Drops for Flat Ceilings
Fur down trusses—also called F trusses—are perfect for areas like closets or bathrooms where you want a flat ceiling within a vaulted space. These trusses extend down from your scissor trusses and give you a clean, consistent flat ceiling. You can even hold the end vertical back to create a plant ledge. It’s a quick, repeatable solution that removes the need to frame that area separately.
Valley Over Frame: Smoothing Out Complex Rooflines
When ridgelines run perpendicular to each other, you need a way to transition between the two. That’s where valley over frame trusses come in. These are graduated trusses that step down gradually to fill in that valley area, guiding water to where it needs to go and preventing pooling or runoff issues. This system gives you a clean transition and structural continuity where two rooflines intersect. If you’re building anything with a T-shaped roof or intersecting wings, this is your best friend.
Lay-In Gable: Getting Back on Grid
Hip roofs are made from flat-topped trusses that get taller as they go in. The problem is, those trusses end up more than two feet apart, which isn’t great for laying down plywood. That’s where the lay-in gable comes in. This truss has vertical studs placed every two feet, which helps tie everything together and gets your spacing back on track. You’ll also hear it called a purlin frame or hip-over-frame gable. Different names, same purpose. Ask for it by any of those, and your truss manufacturer will know exactly what you mean.
Piggyback Brace Frame: For Tall Roofs and Safe Installs
Some trusses are just too tall to build and ship in one piece. When that happens, we split them into two: a base truss and a piggyback truss that sits on top. That base truss needs to be braced at two-foot intervals, which is a lot of work if you’re lifting individual purlins and braces up to roof height. Instead, use a piggyback brace frame. It’s a prebuilt frame with verticals and diagonals already in place, spaced just right. Framers can lift it as one piece and get bracing and purlins installed in a fraction of the time.
Rim Truss: Built-In Blocking at the Floor Line
In floor systems, we often want blocking or bracing at the edge of our trusses. While a ribbon board is the preferred method—a single two-by-four notched into the end of each truss—it doesn’t work in every case. That’s where a rim truss comes in. It's manufactured to match the layout, and it installs just like a rim joist. The rest of the floor trusses are built an inch and a half short to accommodate it. You just place it and move on—no extra site work required.
Floor Girder Truss: Openings Without the Hardware
Sometimes, you need an opening in a floor system and don’t want to mess with hangers. A floor girder truss is a great solution. It's built slightly shallower than the rest of the floor trusses and includes openings for mechanical, electrical, and plumbing to run through. Other floor trusses tie directly into it with a double top chord, meaning they rest right on top. No hangers, no extra material, no extra labor.
Bring It All Together
Accessory trusses don’t always get the spotlight, but they solve real problems that show up during framing. Whether it’s for a ceiling transition, a tricky roofline, or mechanical openings, these components are designed to save time, money, and stress. Talk to your truss manufacturer about these options before your next job. It could mean fewer cuts, faster installs, and a smoother build all around.
