For a 3070 single door the frame s rough opening would be 40 1 2 x 86 1 4 wood stud walls.
Masonry opening for 36 door.
Rough opening overall frame width plus 1 2 and overall frame height plus 1 4.
Getting the rough opening size right the first time will save you from frustration when installing your doors.
Installing doors in new block walls dre for wood frame doors we would size the masonry opening about 3 wider and 1 5 taller than the door rough opening.
For fire rated openings drywall must extend at least 1 2 into frame.
This will give you room to space the door frame off of the sub floor.
When using masonry frames in cinderblock walls the rough opening must have 4 more in width and 2 more in height.
Normally a shim space is allowed both vertically and horizontally to allow the installation of tapered shims to correctly position the window or door unit.
You should add 2 1 2 to the height of the actual door.
Rough opening overall frame width plus 1 2 and overall frame height plus 1 4.
When the block is done set a rough buck of salt treated 2x4 using anchors or lead shields into the block.
The masonry opening will be calculated to allow the necessary additional room for the adjustment and correct installation of the window or the door.
Just add 2 to the width of the actual door size.
Of course we normally do this in an 8 thick block wall with 2x4 rough frame.