Final answer:
In post-and-lintel construction, a lintel must have sufficient bearing on each side of the door jamb to properly support loads. The minimum bearing is commonly around 150mm (6 inches), but specific building codes should be consulted for exact requirements.
Step-by-step explanation:
The question pertains to the structural engineering concept known as post-and-lintel construction, which is a system where a horizontal beam (the lintel) is supported at its ends by two upright posts or columns. In the context of doorways or openings in buildings, the lintel must have sufficient bearing on each side of the door jamb to support the loads above. While the exact bearing requirement can vary based on the design and materials, a common rule of thumb for minimum bearing is around 150mm (6 inches). However, local building codes and engineering practices should always be consulted for specific requirements. The effective distribution of load by a lintel is crucial as without adequate bearing, the potential for structural failure increases. This has been addressed in historical construction through methods like corbeling and the use of relieving triangles, or in modern contexts through precise engineering calculations.