Walls – Making sure this wall is just a partition and not load bearing

Determining if this segment is load bearing should be evident to a competent contractor. There are a few things to look for. You have to look above and below the wall in question. In the floor or attic above, you have to determine if there is structure bearing down directly or via headers to this wall segment. Next, you need to look below in the basement level to see if a beam, post or other structure is directly below the wall segment carrying the load to the foundation. While not always true, this wall segment may be load bearing if it is parallel to the longest dimension of the house, usually perpendicular to a gable end and located half way between the two longest exterior walls. There are a few methods of framing that could make this a load bearing wall, even if you have full trusses for roof support, ie; ceiling joists that rest on a center beam directly over the wall in question. As I said, most competent carpenters could look at this and determine it's load bearing status. Obviously, a set of plans would be helpful as well. Even if it is load bearing, a good carpenter will be able to design a header to span the new opening, support the load and allow you to remove the section of wall you want gone.

I see rafters in your pics, not trusses. Regardless, in general, you are right that bearing walls don't normally run parallel to the rafters. If it were load bearing, there should be a kneewall (2X4's) built from the rafters or a header down to the double plate you spoke off. Also, in the basement level, you would see a beam with posts to the footers directly under the subject wall. The only unanswered question I have is, if the addition roof is being supported to that wall? I do see in your pic a small knee wall from the rafters to something below, but not sure if that is part of the wall you want to remove. Summary, if there are not structural supports going from the rafters to the double plate of the wall you want to remove, it most likely is not a supporting wall.