Final answer:
The required fire rating of a garage door that opens into the dwelling is typically 20 minutes according to the International Building Code (IBC).
Step-by-step explanation:
To determine the required fire rating of a garage door that opens into the dwelling, you need to consider the building code requirements. In the United States, the International Building Code (IBC) sets the standards for fire rating requirements for various elements of a building, including doors. According to the IBC, a garage door that opens into the dwelling typically requires a fire rating of at least 20 minutes. This means that the door should be able to withstand fire for at least 20 minutes before it starts to fail.