A lintel is a horizontal member and structural window component. In architectural terms, lintels can execute a number of tasks, from being purely ornamental to adding actual supportive integrity to the design. Lintels are also commonly found in engineering loci outside of windows, such as in portals, doors and fireplaces.
Throughout the history of architecture and design, lintels have played a significant role, most especially in the basic post-and-lintel system used since classical antiquity and perhaps even earlier. The system involves two vertical posts or beams, with the lintel or horizontal piece laying across their tops. Both the lintels and the posts are designed to bear weight without buckling, crumpling or bending. The essential design of the lithic structures at Stonehenge is a fitting example of the concept. In windows particularly, lintels perform the same function.
In many homes, window lintels are commonly fashioned out of stone or wood, and are used to divert the weight of the roof and walls away from the actual material of the window, namely the glass and other elements. Additionally, lintels can aid in heat retention and other aspects of energy efficiency by providing further seals against exterior elements. In these cases, the lintels may be made of even more durable and specialized materials, such as steel or concrete masonry units. As lintels are often broad and wide, they also afford places for decorative ingenuity, such as with stone or wood carving.