"crow's nest" on top of engineered trusses

[eric]

Hi there,

Got a question. First off there's no building code in my county so that's not an issue.

I've got engineered trusses on a 24 foot wide building at 4/12 pitch. On the front 10 feet of the building, about three feet on either side of the peak, I intend to put 10 foot 2x12's ripped to match the pitch of the roof to make them level with the peak. These 2x12's will span 5 trusses and will be toenailed and tied to the trusses with some sort of simpsony tie thing strapping. On top of these I'll put 6 foot 2x6's as joists, then sheeting for the floor, then a 6 foot stud wall on the south side and 4 foot on the north for a shed roof with 2x6 rafters. There will be a 3x5 window, a 3x3 window and two 2x2 windows in the walls. There won't be anything but people inside of it so the only weight really will just be the materials.

Hope that description makes some kind of sense.

The winter before last this roof supported more than 4 feet of heavy wet snow for several months. I think it can support this crow's nest, what do you think?

- Eric

[eric]

I should mention it's actually 6 trusses over the ten feet, 24" o.c. I think is the designation. And also, on both ends of this ten foot span, there are walls from the slab floor to the bottom of the trusses. This fact plus the 2x12's makes me think it will be totally fine. I'm pretty set on it. Thanks for any ideas you folks might offer.

[Don_P]

If you are bearing in between panel points, in between where the webs and chords are connected, either above or below, it is not too hard to overload the truss members.

The correct way is to go back to the truss plant and sit down with their engineer. They can usually come up with a fix to safely handle unanticipated revision to the truss plan.
or,
If you can run support from the bearing walls below up to the structure above...bypassing loading the trusses, then it is no problem at all.