2×12 rafter to open-web floor truss connection
pietrasm5
| Posted in General Questions on
Does anyone have a detail for connecting a 2×12 roof rafter to (or on top of) an open-web floor truss system. There will not be a structural ridge beam so it will need to be able to withstand the tension force needed to prevent the rafters from separating from the wall plate (similar to rater ties).
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Table R802.5.2 has some guidance: https://codes.iccsafe.org/content/IRC2018/chapter-8-roof-ceiling-construction#IRC2018_Pt03_Ch08_SecR802.5.2, but that's really for rafter-to-joist connections. I don't know of anything prescriptive that addresses this but I often have similar conditions; I do my own math to calculate the outward thrust or work with licensed engineers to do so. The lower the pitch, and the greater the vertical load, the greater the horizontal load.
I realized that I left out some information. What I usually do is install floor sheathing above the ceiling joists, then fasten one or more 2x6 plates at the edge of the sheathing, then birds-mouth the rafters over the plate(s). You can eliminate the sheathing if necessary.
This one has applied rafter tails and a secondary gusseted rafter, but the same general idea.
You can also look at trimmable end trusses. These have more wood at the ends which you should be able to pack out to get a solid connection to the rafters.