I have a problem (only slight) with a log home that I've contracted for purchase. It's a 1500 sq. ft. structure with a great room. The home was re-roofed last year and I just did a physical inspection.
There are no open rafters typical of conventional log homes.
The area over the great room is drywalled and the trusses above the great room are 2x4, with 2x4 cross members attached to the front and back walls.
The problem is that the area over the great room is not supported by as many interior wall as the area to the rear of the house containing the bedrooms.
We noticed a slight sag in the ridge line from the area of the ridge where the great room starts to the far end of the house by the chimney. Upon further inspection, we noticed that some of the nearly vertical support members of the trusses were bowed. We feel that this is due to lack of cross-bracing of the trusses. In effect, the trusses were installed with no cross-bracing (a surprise indeed).
Further, there is no ridge beam or central beam running the length of the house above the ceiling.
One scenario would be to run a 1-2 vertical joists from the attic floor clear through to a footing in the crawl space beneath the first floor, then add a beam on the attic floor and collar ties to the trusses. We could then add two vertical joists in that span.
A simpler method (which we are doing now) is to add cross-bracing to the trusses and hope that this solves the problem.
A third method would be to laying a 20-30' beam to the attic floor, spanning between the area of the home supported by lower interior walls and the log wall at the other end of the home by the chimney. Installation of collar ties and vertical joists would then be done.