I am doing some remodelling work in my basement. I am paying a lot of attention to sound proofing. Currently the ceiling in the basement uses TJI's that are spaced at 16" and 12" and span 20 ft lengths. I am planning on building a room within a room. Thus I will be putting in ceiling joists that are supported by the stick walls on both sides of the basement ( a 20 foot span), and are not tied at all to the existing floor joists above. The new ceiling joists are going to be placed in between the spaces in the existing joists and hanging an inch or two below the existing TJI's. Because of this, I won't be able to use cross-bridging, since basically there will be an existing beam between each of the new ceiling beams. Through research it appears that floor joists that are 20ft long, would require 3 sets of cross-bridging (every 6 feet). But in this case, there is no load on the new ceiling joists.
I am debating using TJIs or 2x10's. The TJIs cost more than double the 2x10s, but don't require any bridging. Since the 2x10's (Spaced at 24" centers) will only be supporting the ceiling drywall (2 layers of 5/8" drywall), and no "live" load, do they need cross-bridging?
I know this isn't a typical configuration, but soundproofing is a must in this situation.
The earlier codes required bridging with 2x12's, on floors, not ceiling joists. Not required on ceiling joists as no need to distribute a concentrated load, their purpose. The ends must be secured to prevent rotation and must be fire-blocked from the ceiling above as it is now a drop ceiling.
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