The rough opening of an interior door is two inches wider than the width of the door and two inches higher than its height. Thus your rough opening width is 38". A typical interior door has a height of 80" which would require a rough opening height of 82" but check your door to ensure that is theheight.
You can't - the door you have is one foot too narrow. Take the door back and get one that will fit.
Garage Door PhoenixGarage Doors come in standard sizes such a 8x7, 9x7,10x7,16x7,18x7 , these are the size for your typical 7 foot high Garage door they also come in the larger 8 foot high and 10 foot high sizes ,
The door will fit an 18 foot wide building. You might not be able to store two cars in it though.
Depending on how the garage is constructed, you will probably need to reinforce the wall above the door. The header for each 8 foot door is supported on the center post. If I were doing it, I would cut the inside header in the middle of each, take out the section on each towards the middle and replace it with one board across both headers. Then use plywood on the wall above the opening. Build in the sides to 16 foot and hang the door.
Open the drivers door. The lever is next to the opening of the door by your left foot.
8 or 9 foot, either one is common.
A sagging garage door is, basically, a structural engineering difficulty. While the most thorough and best approach to remove the problem is by having a structural engineer in to look at the garage, take measurements and fix the sag; there are things you can do yourself to fix the problem, although they may not be as permanent as having a professional fix it.
Unless you are replacing a 16 foot wide window, you will need to install a header. Your best bet to span that distance is a laminated beam or other engineered lumber, and you will need 3 jack studs supporting it on each side. Since you are making a structural change, you will need to pull a permit and have the work inspected. Temporary bracing will be needed to support the roof while installing the beam. Make sure the rough opening is level and plumb, or you will have trouble with the garage door later on. While I encourage DIY's, this is probably more than a homeowner can comfortably handle, so get a few quotes before hand. Take the molding off from the inside of the door where the window goes, measure the area where the window goes, go to hardware store buy the glass to fit the measurements, put the glass in the door and with small tacks and nail the molding back on,
16 feet wide for a double garage door even though as a builder i install 18 foot wide doors when i can. This allows more room between the two cars when parked inside.
The average dimension for a tandem garage with only one door for vehicle access is a 14 foot door that is about 14 feet high. The interior space might be about 16 to 20 feet wide and 13 to 16 feet in depth. A two-door tandem garage is going to be about 16 to 20 feet wide and 16 to 20 feet in depth.
A bathroom door is 2 foot door or a 2 foot 4 inch door.