Make the rough opening 3 wider than the garage door.
Rough framing for 2 8 x7 garage door openings.
Install the header jambs and center pad of the frame using a 2 x 6 lumber for the header jambs and center pad.
Getting the rough opening size right the first time will save you from frustration when installing your doors.
However the correct answer should be that you want the finished opening to be the same size or slightly smaller than the door so the rough opening will depend on what you are putting on the sides of the opening and underneath the header.
Next you will need to know your door height.
Use shims and or caulk to seal gaps between wall and frame.
99 of the residential garage doors that we run across are different than these widths.
Framing rough opening sizes are really quite simple.
Leave at least 5 of space on the sides of the door.
1 2 or 1 in one direction of the other will won t typically cause you to have to shop for a non standard garage door size.
Standard garage doors in our area are 8 9 16 and 18 wide.
The rough opening would be 40 1 2 x 86 1 4 for a 3 0 x 7 0 door frame.
Make sure to allow for an uneven floor.
Step 1 measure the old door if you are replacing an existing door with one of the same size or the new door of choice if you are building a new garage.
Frame the rough opening to a height that is 1 5 taller than the door that you have selected.
Of frame is 40 x 86 as the frame face is 2 around all 3 sides.
Header the header is ideally a minimum 12 wide micro laminated beam that spans the width of the garage door opening.
Timely prefinished interior steel frame.
If opening will be perfectly level and plumb 1 2 to 3 4 smaller than door.
Just add 2 to the width of the actual door size.
Depending on your opening the lumber width will be 6 to 8 wide.
You should add 2 1 2 to the height of the actual door.
The rough opening is equal to the size of the door but you need to figure back head and side room before choosing and installing the new garage door.
To finish the opening cut the header and jambs from 2 lumber.
Header requirement 2 at minimum the header should be 12 wide with doubled 2 4 at opening and ceiling running the width of the door with a 2 4 in the center of the opening for the center bracket to attach to.
If sides are not plumb consider a flush door instead of a raised panel to make it less obvious.