Sistering engineered I-beams

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Old 02-23-07, 01:39 PM
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Sistering engineered I-beams

I was wondering if sistering both sides of an engineered I-beam would be much benefit to stiffening a floor. I have a 20'-9" foot span with G-P GPI 40 ( 2 15/16" LVL flanges with an 11 7/8" depth ) wood I beam joists and have about a 3/8" dip under a knee wall six feet from one of the supported ends. It also has a little more bounce than I would like. I was thinking of ripping 3/4" plywood 9 1/8" wide and glueing/screwing it to both sides of the web (between the flanges) and offsetting the butt joints between the added material. Any thoughts?

I forgot to mention that the joists are on 16" centers. This area was originally built as a "bonus room" (over the garage) and the architect and 2nd floor system designer originally specified 9 1/2" deep joists for this application (for L/360 live load deflection). I had the lumber supplier increase them to 11 7/8" (to make the ceiling height in the garage a standard 8' with 9' walls surounding the garage). The joists do not sit on top of the supporting walls but are hung on a rim joist or band. The subfloor is 1 1/8" T&G OSB with another layer of 7/16" OSB overlapping all of the joints.
 

Last edited by charm3; 02-23-07 at 03:16 PM. Reason: Added information
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Old 02-25-07, 08:32 AM
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I did find out that what I am talking about is actually called "web stiffening" and is covered somewhat on the G-P website. I also learned that my floor was designed to minimum standards (L/360) for the application and I would have been better off with loading designed to L/480.
 
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