I have a 2 foot second floor cantilever. As it stands right now I look up at the bottom of the TJI’s which extend out to carry the floor and wall above. How do I finish this underside. My soffit material is 11/32 rough cut plywood. Do I sheath it with OSB then the soffit material? What about vapor barrier (I’m using 15# felt on the walls)? How do I make the transition from the insulation that will fill the space with the area inside the first wall between floors that won’t have insulation? Blocking this area will be difficult because of the shape of the TJI’s?
Discussion Forum
Discussion Forum
Up Next
Video Shorts
Featured Story
Upgrading the footings and columns that support a girder beam is an opportunity to level out the floor above.
Featured Video
Highlights
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Replies
All the I-joists I'm familiar with require blocking at the bearing point for a cantilever. Difficult or not, your inspector will probably require it. For the soffit, why not 1/2" MDO ply? Smooth and paintable, it would seem to be a good solution. As far as the insulation and vapor barrier in the cavity, the back side of the MDO soffit and rim joist would need it. I'd insulate with foil faced material the bearing wall below as normal, stopping at the bottom of the I-joist blocking and then pick up in the cavity as described above. Obviously that area would need to be done either prior to the joist blocking or prior to the soffit material.
Al
I would treat the underside like soffit with a vaporbar and pack with insulation but it seems from your description that you have not completed your framing yet. The TJIs have to be blocked per the manufacturers specs for cantilevers or you can expect failure. This is as absolute as the laws of gravity.
I get the message on blocking but thats not my question. I am not familiar with what a 'vaporbar' is. Is that lazy typing for vapor barrier? I don't put any vapor barrier in my soffits. just the 11/32 pylwood and vents. that space is open above the truss blocking to the attic area above the insulation. If I need vapor barrier on the outside of the wall and moisture barrier against a heated space then I propose to place 6 mil poly on the underside of the floor and against the blocking, pack the area with insulations, cap the underside with 7/16 osb, wrap the felt down the 2nd story wall, across the 2' cantilever underside, and onto the 1st floor wall. Then I will place the 11/32 rough cut plywood over the osb and trim all the corners. This essentially treats the cantilever space like an exterior wall cavity.
yes is lazy typist here.
Mainly need to prevent airflow from underside into floor space. Blocking is not hard thing to do, except for a lazy framer.Excellence is its own reward!