How many inches of bearing is required for the ends of rafters or ceiling joists on wood or metal?

The correct amount of bearing required for the ends of rafters or ceiling joists on wood or metal is 1.5 inches. This requirement is based on the structural needs to ensure that the load from the rafters or ceiling joists is adequately supported by the bearing surface. A 1.5-inch bearing provides sufficient surface area to transfer loads effectively, which is essential for maintaining the stability and integrity of the roof or ceiling structure.

The 1.5-inch standard relates to typical lumber dimensions and the associated guidelines in the residential code. This requirement ensures that the rafters or ceiling joists are securely anchored and minimizes the risk of failure at the connections.

The other options do not meet the established standard for this type of application in construction. For example, requiring more or less bearing may lead to structural inefficiencies or complications, which is why the code specifies a minimum of 1.5 inches.