Yesterday (Monday) I spent beefing up the studs forming the left knee wall with methods inspired by those Stuart uses for hanging heavy doors. This is where the exhaust silencer goes. Although constructed correctly and fine for a small bit of plasterboard, the existing stud wall was too weak for the silencer. The vertical stud on the left of these photos was only 20x50mm cross section. All studs were nailed and a bit wibbly wobbly.
It took a bit of work to figure out how it fits in the house structure. The wall to the left (with the room door in it) has its own studwork - sole plate, top plate & verticals. The plasterboard is attached to this, not directly to any of the joists or rafters. The last (short) vertical ends before the first vertical of the roof truss, and does not touch it.
In contrast, the wall to the right that extends out to the balcony is formed from several sheets of plywood that are directly attached to the rafters / roof truss. So although the existing studwork might look a bit funky, it was done in a manner that preserved the "leaves". My reinforcements keep this system.
First up, remove all old knee wall studwork. Then brace the diagonal corner of the main wall with a sheet of OSB. In this photo it looks like the OSB is touching the roof truss but it is not.
A smaller brace at the bottom corner.
New 89x38mm stud in place. Consistent with previous studwork, it does not touch the rafter above the sloped part, therefore will not become a vertical load bearing element.
The stud on the right is part of the roof stucture "horizontally" by virtue of being attached to the structural plywood. Therefore I reinforced this one horizontally with a nogging to the roof vertical. Again, the stud stops short of the rafter so no vertical load from the roof is imposed.
Overall view. The studwork is now very solid indeed.