We have a 3 car garage that is 36' wide. It has a 18' door and a 9' door. With the doors on both cars opened wide we still have plenty of room between to walk. (We park 3 cars in the garage) Spend a little extra on a larger I-beam so a post is not needed. It's your choice. I like that I can load up with packages or sacks from the store an carry them into the house with out bumping into the car or tring to get aroud an open door. Around here, we get snow in the winter which means the cars can get very dirty with road salt and sand. You don't want to rub up against the car with good clothes on. Many of our neighbors have garages with 16' and 8' doors. I have several neighdors that park their truck in the 8' bay. They have to fold the side mirrors in so they can get it in the garage and fold them back out after backing out. That is another hassle that I would want every day.