Hi, I am new, and my name is Adam Kadmon, 4 years ago I built a 3 car garage with an attic storage space. Since then I have used a ladder to place stuff in the attic, but now I wish to install a pull down stair unit. I have 16" on center roof trusses, instead of 24" on center, and must cut one truss to intall 24" stair package... but how may I go about it without damaging my roof structure? Thank you, Adam Kadmon

you need to build a header between the to ceiling trusses. To do this take some osb on both sides (cut at the angle) of the roof, make sure the osb is resting on the bottom of the truss and that it is fully making contact with the rafter part of the truss, use screws or nails, code wise they would want you to use nails 8penny and nail it good.
do this to both side of the truss you have to cut, you should need to make 4 pieces of osb.
try and also use half pieces of the osb, you need to cut it as big as you can for more support. After you get it braced up, run a double band 2x6 on all 4 sides, I don't know off hand what the measurements are for the rough opening, I'm thinking the width is 22 1/1 and lenth is 45 or 54" just read the instructions to be sure,