Standard joist spacing for the installation of attic flooring materials is 16 inches on center oc meaning the distance from the center of one joist to the center of the next joist is 16 inches.
Reinforcing attic rafters.
When using fiberglass insulation the pink stuff the attic roof rafter will need to be at least 16 deep.
Keep the spacing 4 feet apart at most.
Reinforcing the connections between the rafters and the walls will help prevent your roof from collapsing.
Install these over your existing horizontal 2x6s 2 feet from the roof edge inside and paralel to the roof ends crosswise from your existing 2x6.
The easiest way to straighten rafters is to jack them into position.
Move the jack in increments of one inch to allow for the roof to be able to move with it without cracking.
3 place a two by four against the rafter along the bottom.
Place a ladder or stepladder against the rafters to allow yourself to climb up to them.
In an older home a typical roof rafter can range between 2 4 s to 2 8 s.
Divide this in two and move to the center point of this half of the joist.
Step 2 measure the length of a ceiling joist from the midpoint of the garage to the wall of the garage.
However the trick to this process is to do it very slowly so it may take a few weeks before you get the rafter into a position where it is straight again.