In some areas, doors between houses and garages must have a fire rating. Twenty minutes is common. In other areas, exterior-type doors are adequate. A one-and- three-eighths-inch-thick solid core door is usually acceptable.
Garage doors separate the indoors from the outdoors, and should therefore be weather-stripped. Another good reason for weather stripping is to keep automotive exhaust fumes out of the home.
Many jurisdictions require that garage doors be self-closing. They don't want people leaving the door open into the house. If an automobile in the garage is running, carbon monoxide fumes can enter the house. This is a life safety issue.
Operate the self-closing system to make sure it works, by opening the door and letting it go.
Because garage doors may not be perfectly tight, it is considered risky to have a garage door that opens into a sleeping area. This is not allowed in many areas.
It's a good idea to have to step down into the garage as you leave the house. This is because the garage floor may have water on it that we don't want to run into the house. Low-lying gasoline fumes will have a more difficult time getting into the house if there is a step up from the garage.