Extending roofline from I-joist rafters
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I am extending the roof on a house built with 2-5/16 wide by 16” tall TJI I-joist rafters. Sections of I-joist were used as blocking instead of rim joist. All of this is covered by 3/4” MDF. I am trying to figure out the acceptable method for attaching a ledger board to extend the roofline 7 feet on to a beam for a porch overhand.
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http://floridabuilding.org/upload/PR_Instl_Docs/FL6527_R1_II_TJ-9001%20102006.pdf
see page 10.
Drawing seems to indicate it is ok to install an LVL rim joist to the ends of the I joists and have them extend up to 5 inches past the top plate of the wall.
Since you do have access to the ends of the I joists, you might be able to install a suitable LSL rim joist and secure the ledger board to it.
Might need local engineer analysis and building office OK.
Not sure if that would be sufficient since the rom board still wouldn’t be sitting on the crown plate. Thoughts? Came up with 2 options:
1. cut blocking ijoists and sister longer 2x rafters to the ijoist rafters, resting against the top flange.
2. Install web stiffeners to both sides of the blocking ijoists (two 15/32” CDX on each side) then 23/32” CDX over entire length, acting as a sort of rim joist. Attach 2x ledger board with structural screws and attach rafter hangers to it.
For the first, rafters need solid support, if you want to cut into the blocking, and run the rafters over the wall, they need solid wood between them and the top of the wall, and enough support to keep the rafters and whatever they sit on vertical. Blocking needs to be replaced as well. (could do both at the same time)
for the second, I joist webs are not designed to take loads. this option replaces an LVL structural element with CDX.