Fire trucks and engines come in all different sizes. The largest one I ever drive was 13 feet wide and 33 feet long. It was an Air Force Crash Truck called a P-2. Today there are even bigger fire...
In the US, they are often made of wood or metal. Sometimes they are part of a firewall that is part of a fire rated corridor, and have a rating (such as 1-hour). Rated doors are solid wood or mineral...