I'm trying to install a ceiling-mounted kitchen fan. I have a few options:
* Offset the recessed hood relative to the stove.
* Build a box to lower the entire package.
* Make a notch in the lower frame to achieve something nice.
The last option I hadn't really considered as an alternative but started looking into the forces, and perhaps it is possible to make a notch. What is needed is to notch a 45x220 by 55mm over a distance of 285mm. Would this be possible with some kind of reinforcement?
* The truss is supported by a ridge beam.
* Floorboards screwed and glued on top of the lower frames.
* Offset the recessed hood relative to the stove.
* Build a box to lower the entire package.
* Make a notch in the lower frame to achieve something nice.
The last option I hadn't really considered as an alternative but started looking into the forces, and perhaps it is possible to make a notch. What is needed is to notch a 45x220 by 55mm over a distance of 285mm. Would this be possible with some kind of reinforcement?
* The truss is supported by a ridge beam.
* Floorboards screwed and glued on top of the lower frames.
In principle, it's one of the most inappropriate things you can do to a floor joist, notching it at the bottom in the middle of the span. If accessible, you can reinforce the joist to compensate for the notching, for example by screwing and gluing battens on both sides at the top. Additionally, the notching area should be more than adequately covered with screw-glued plywood on both sides to prevent cracking. The question is whether it's worth the effort?
Yes, fully aware that it's not something you do in the first instance, hence it hasn't been an option before. I can access the beams, so there are no problems reinforcing them in every possible way. But as you write, it's probably not worth the hassle. I'll have to build a box underneath instead. Feels safer. 
this way I can avoid worrying in the future about my notched floor beam.
this way I can avoid worrying in the future about my notched floor beam.