Trusses where the bottom chord flexes, cambered

[Frst11]

Hello,
In a recently purchased house, there are two rafters that are problematic where the lower arms noticeably sag due to warping.

During inspection, it was pointed out with suggestions for action, and for me, it seems logical that the sag has occurred since the span is somewhere between 6.60 - 6.80 m.

I would like to discuss this with the forum.

In total, there are 12 rafters spaced approximately 1.20 apart. The majority of the rafters are also supported by interior walls but not all, 4 are lacking support from interior walls.

10 rafters are reinforced with braces on each side of the rafter approximately 3.00 m apart. Collar ties are missing on all.

The rafters are 45x195 c24 with a pitch somewhere between 40-42 degrees. The roof covering is metal.

My idea is to support them with braces like the other rafters and add collar ties to all rafters.

The questions are,
- Will the collar ties contribute to anything?
- Is it sufficient to add braces as described above to the sagging rafters?
- Would I benefit from adding intermediate supports?

Image 1: shows rafter that is sagging


Image 2: shows other rafters

 

[Dowser4711]

How old is the roof structure?
Have there been any changes to it or the interior walls?

 

[Frst11]

How old is the roof structure?
Have there been any changes to it or to the interior walls?

Built in 2001 and is an extension. The trusses are outside the actual connection to the original construction.

I don't have the exact history of the rooms but I think I can see that one room has been removed, but that room would have been some distance from the trusses in question.