I want to put a new door in my garage out to the backyard. There isn't a door there now so I need to cut the opening and frame it. This is something I've never done before. I've done a lot of reading about cutting the opening, king studs, jack studs, cripples etc. and I'm comfortable with most of that but I don't know how to determine the height of the opening. Please look at this photo. The garage wall has a cement footing around it that is around 6” high. On top of that is a 2x4 and then on top of that is another 2x4 which I guess is the exterior wall. Which of these 2x4s, if any, do I cut away for the door rough opening? I’m worried about getting the rough opening cut right for the height. Which board does the door rest on?
Door openings are generally about 2" larger that the outside dimensions of the door. A 36" door should have a rough opening of 38x83. The threshold can sit on the bottom plate. You will need a small step.
Thanks for the reply. I understand that the opening height needs to be around 2" more than the door itself but from where do I measure the height based on this photo? Would you cut away just the first 2x4 and measure up from there or both and measure up from the cement?