Just add 2 to the width of the actual door size.
Masonry opening for 36 door.
For fire rated openings drywall must extend at least 1 2 into frame.
Framing rough opening sizes are really quite simple.
This will give you room to space the door frame off of the sub floor.
For a 3070 single door the frame s rough opening would be 40 1 2 x 86 1 4 wood stud walls.
The example for this is if you want a 3070 36 x 84 door and frame in a cinderblock wall then the rough opening required is 36 4 x 84 2.
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.
Of course we normally do this in an 8 thick block wall with 2x4 rough frame.
Rough opening overall frame width plus 1 2 and overall frame height plus 1 4.
You should add 2 1 2 to the height of the actual door.
When the block is done set a rough buck of salt treated 2x4 using anchors or lead shields into the block.
A opening width 2 b opening height 1 the rough opening would be 38 x 85 for a 3 0 x 7 0 door frame.
Getting the rough opening size right the first time will save you from frustration when installing your doors.
When using masonry frames in cinderblock walls the rough opening must have 4 more in width and 2 more in height.