/diy/ - Do It Yourself

>>2010806
They would not provide any racking support. A common way of doing it back in the day was with a shear brace. This would normally be a 1x4 that ran from the top plate at the corner stud across the wall at 45 degrees down to the bottom plate. It was typically 'let in' (placed in notches in the studs) from the outside and nailed to each stud. You might also see diagonal blocking (picture related), another common method. Modern construction uses large sheet material to provide the bracing. It doubles as sheeting, is much stronger, goes up faster, and is cheaper. If your external walls are not covered in 4x8 sheets of plywood or OSB then you need some kind of shear bracing.

That said, I don't know for sure why they are on the inside of your external walls. Insulation? Noise reduction? I can only speculate. What was over them? Drywall?