I am trying to install a ceiling fan in a downstairs bedroom that has structural lumber (wooden "I-Beams") for the ceiling joists. The original plastic box that I removed was nailed adjacent to the bottom of the "I" with a 4 inch hole that is just next to the bottom of the joist. One nice thing is that I have about 9 inches of space between the ceiling and the floor above in this space.
The problem I see is that all the retrofit braces seem to assume dimensional lumber is used. The bottom of the "I" only is 1.5 inches deep, then the structure is indented in a about a .5 inch or so where the plywood is. Most braces try to grab, at the minimum, right at 1.5 inches (the Reiker 33310) and most are even taller (e.g. Reiker 22200). I don't think a 1.5 inch brace would fall down but I the teeth might ride up over the edge, allowing lateral movement. Overall I am not as impressed with this method based on what i have.
I recall seeing a different kind of brace (at Home Depot I recall) that has a bracket that is screwed into place when a joist is next to the opening. The fan actually hangs from this bracket that sticks out over the center of the exisitng hole and a box is mounted to the bracket to contain the wiring. I am not sure how high up on the joist the bracket is installed, but if I put a piece of lumber (using oak or hickory about 6inches long and 3.5 inches wide) on the bottom of the joist (screwed and glued into place) that would "fill out" the beam profile. I could then screw the bracket into the lumber using also epoxy or gorilla glue on the bracket to further affix it to the joist. This would seem to be strong enough to hold a ~30 lb fan.
If anyone knows who makes the "side bracket" hanger or knows of a brace made for structural lumber I would be very grateful. Google searches have been relatively futile. I hope to learn much more following this thread and newsgroup