building and construction

The door assembly should show the rough opening. However, are you installing a wood frame door? If so, not an easy task since you wont be able to nail the trim. I usually build a subframe section that will screw to a close fit metal stud and sit in the botton and top track. That way, you can fit the door and trim.

Thanks... so to fit a 36" door how much shold i make the steel frame to make this happen...

As a rule, you make the rough opening 2" wider than the door so a 36" door would be 38" RO. Measure the total jamb length and add 1/2" and a normal RO is 81 1/4 -1/2". Your metal studs would fit flush against the outside of the subframe. So the metal stud RO should be about 44" using a jack and king stud layout with a wooden header. simplest way is to build the subframe, set it in place and then move the metal studs up tight. Screw from the metal stud side into the wood stud to fix it then put on the drywall. You should have a 38" X what ever the heigth is plus 1/2". Insert the prehung door, and use use wood shims to square the frame.