Mastering Roof Framing: Prefabbing Trusses and Valley Cuts
(This is the sixth in a 10 part series. Credit: Akribis Leather. Luke Riemer, owner, was the framing contractor we hired for our build. The project consisted of a carriage house, garage extension with suite above, and renovation/expansion of the existing residence. All 3 phases of the project had some timber framing elements. Text below is a cleaned up transcript of the video above)
Roof framing can be a complex process, but with careful planning, organization, and attention to detail, it becomes a smooth, satisfying task. In this post, I’ll walk you through my method for prefabbing trusses, setting valley trusses, and efficiently handling roof sheathing.
Organize and Prep Your Trusses
The first step is organization. Place a couple of 2x10 beams and stack your trusses in order. Set aside trusses for the gable ends to make those sections easier to prep.
I like to sheet the gable end first and place it on top of the truss that will sit directly behind it. This allows me to handle all layout work—like rafter tails, ladder placement, and fascia lengths—before assembly, ensuring everything is dialed in and ready to go.
Setting Trusses in Place
When setting trusses, make sure your first board has at least 20 inches of cantilever. Lock initial trusses in place with 2-inch pan spikes, then lay out ladder pieces and gable placement.
For blocks at the bottom of the trusses, I cut them at 45° to provide cross ventilation and ease of nailing. When installing trusses between girders, leave a small gap to make placement easier, then adjust the girders to snug everything into place.
Ridge Blocks
Ridge blocks should be slightly shorter than the mathematical calculation—22 7/16 inches for a 22 1/2-inch block is a good standard. This ensures they fit easily into gang nails and allows for minor adjustments without disassembling the setup.
Pitch Considerations
Working on a 10/12 pitch is challenging. Walking is slippery, so use careful stepping and toe boards where needed. Nine is easier to walk; eleven requires more support. Always prioritize safety while handling steep pitches.
Sheeting the Roof
Before installing valley trusses, sheet the roof planes. Straighten gables and fascia, then measure and snap lines for the width of your sheets. Helper nails along the bottom edge make positioning easier.
Once the first course is nailed, subsequent rows can be installed more quickly. Ensure trusses remain aligned with the layout, and double-check that everything is square and level.
Valley Trusses
Sheet the plane first, then set valley trusses on top. Follow the layout from your truss company exactly—the trusses must go where they are designed to go for the geometry to work.
Snap valley and center lines, then use the bottom chord of the first valley truss to determine its height. Once the first truss is in place, the rest follow mathematically. Use ridge blocks slightly short for easier adjustments and a strong fit.
Tools and Setup
Here’s my preferred setup for roof framing:
- Harness: SA XOFIT
- Bags: LT bag with tape, nail puller, rafter square, stick nails (2-inch and 3-inch), pencil, knife, and chalk line
- Hammer: R1 HV in metal loop
- Extras: Phone pocket clip, helper nails, H clips for sheathing, and space for coils
Lightweight and organized, this setup keeps everything accessible while maintaining safety on steep roofs.
Efficient Valley Cuts
To cut valley and hip sheathing accurately, measure the difference between the short point and long point on a 4-foot sheet. Once established, this measurement can be used for all diagonal sheets if pitches are uniform. Snap lines for both top and bottom edges, mark termination points on the valley line, and cut consistently for clean, precise fits.
Final Tips
- Always follow your truss layout and manufacturer guidelines.
- Take extra care with measurements; slight deviations can compound quickly.
- Work methodically: prep, measure, then install.
By keeping everything organized, square, and level, your roof framing will not only be structurally sound but also highly satisfying to complete. Proper planning, careful layout, and efficient sheeting make what seems like a daunting job straightforward and even enjoyable.
