Under this attic, there is a wall that runs down the middle along the ridge that I am eager to open up. Do you think the wall only supports the floor joists, or is it also load-bearing for the roof trusses? The house is about 6m wide and the infill material in the floor is sawdust, the roof is tile. I would like to open up 3.8 meters and then preferably just have a glulam beam to support the floor joists. Do I need an engineer to design this, or is a builder sufficient?
From what I can see in the photo, there are no roof loads affecting the floor beams. If you want to make a supporting structure for the wall under the attic, you will need both a glulam beam and two columns for the beam to rest on. The columns, in turn, require supports that can handle the loads involved. This amounts to just under 20 kN (approximately 2000 kg) per column.