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.
Rough framing for 2 8 x7 garage door openings.
Leave at least 5 of space on the sides of the door.
If sides are not plumb consider a flush door instead of a raised panel to make it less obvious.
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.
To finish the opening cut the header and jambs from 2 lumber.
Make sure to allow for an uneven floor.
Standard garage doors in our area are 8 9 16 and 18 wide.
Timely prefinished interior steel frame.
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.
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.
The rough opening would be 40 1 2 x 86 1 4 for a 3 0 x 7 0 door frame.
Use shims and or caulk to seal gaps between wall and frame.
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.
Just add 2 to the width of the actual door size.
If opening will be perfectly level and plumb 1 2 to 3 4 smaller than door.
Framing rough opening sizes are really quite simple.
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.
If the door is 7 tall frame the opening 7 1 5.
Install the header jambs and center pad of the frame using a 2 x 6 lumber for the header jambs and center pad.
Header the header is ideally a minimum 12 wide micro laminated beam that spans the width of the garage door opening.
You should add 2 1 2 to the height of the actual door.
Next you will need to know your door height.
99 of the residential garage doors that we run across are different than these widths.
Leave a headroom of 14 or 12 minimum.
Also make the rough opening 1 5 taller than the garage door.