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New deck joists sistered to existing cantilevered joists?

New deck joists sistered to existing cantilevered joists?

New deck joists sistered to existing cantilevered joists?

I am working on a project, 2 story residence with an existing 8 to 10 foot cantilevered deck. All wood framed construction in Southern California. The existing floor & deck consists of 2x10 DF joists that sit directly on top of 11-7/8" TJI joists. The first span is 18ft, which is the interior house floor & then they both cantilever from 8 to 10ft as an exterior deck. Please refer to the attached pdf that shown the existing and proposed condition.

If I sister new deck joists spanning the full new deck length to the existing 2x10 upper deck joists and remove the lower TJI joist at the deck I have some concerns about the actual loading to the new beam supporting the deck and wall above.(noted on attached pdf). Note that there is also a new wood framed shear wall approximately 16 inches behind the new dropped beam, so not the existing 2x10 will be a multi span condition.

The reaction for this condition is what you would expect with a larger gravity reaction on the wall and an uplift over the beam.

The more I think about this solution the more I think that there may be another better/cleaner solution.

What are your guys thoughts, opinions?


RE: New deck joists sistered to existing cantilevered joists?

I'm not sure why you are removing the existing TJI, could you elaborate?

Also, can the existing 2x10 joists support the shearwall load at the location noted? I feel like 2x10 spanning 18ft are pushing the limits at the best of times, throw in a point load and you're asking for trouble.

RE: New deck joists sistered to existing cantilevered joists?

No, the TJI's are remaining below the existing 2x10's at the 18ft span, but after the new dropped beam where the deck begins they will be removed. Then I will add new LSL deck joists from the new dropped beam to the front of the deck. I had planned on sistering(wrong term) the new LSL joists to the existing 2x10 so that the 2x10's can remain in place in order to protect the existing deck surface. As I started thinking about the 2x10 now being supported at 3 places, the back of the garage, the new shear wall and the new dropped beam, in addition to the sttachment to the new LSL's I begin second guessing the reactions and how the deck will perform.

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