In following certain forum threads at, I am surprised at the number of misunderstandings about I-joist installation, considering that all the major I-joist manufacturers have installation instructions. There are specific rules about the size of holes that can be in the webs, and where. The need for end blocking to prevent the joists from rolling is also explained. (Cross-bracing is a separate issue; it helps transfer live load from one joist to the adjacent joist.)

One way to slightly improve floor performance is to increase the thickness of the glued-and-screwed subfloor: For every 1/8 inch increase in thickness above 3/4 inch, there is a 5 percent reduction in deflection for the design load.

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