The photos above, sent in by a JLC reader, show great examples of how not to frame a roof with wood I-joists. The bottom flange of the I-joist — the part that is most critical for carrying the bending forces — has no bearing, either at the top or the bottom.It will not take a large load for this roof to fail. What will the failure look like? Most likely, at the upper end the I-joist webs will tear away from the top flanges. At the bottom end, the webs will split and the roof will come down.
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