Originally published in The Town Paper, Vol. 3, No. 4 - June/July 2001
A lintel is a horizontal structural member (such as a beam) over an opening, which carries the weight of the wall above it. Lintels are usually associated with windows, though such structural members apply to any weight-bearing element or elements over an opening in a wall. They serve as much of an aesthetic purpose as a structural one. Lintels give a visual representation of how the load of the wall is carried across a window opening and down the walls on the sides. Thus both aesthetically and structurally, there are correct ways to architecturally represent a lintel.
Lintels should always extend beyond their opening, overlapping the walls to either side. After all, they need the walls on either side of the opening to keep them and the weight they are bearing from collapsing. Lintels should always be a single element or a single system of elements, with breaks at structurally appropriate locations and rarely directly in the center of an opening. In most cases, it wouldn't make sense for the weakest point of the lintel (a break line in the lintel system) to be at the point with the least amount of support from the walls to either side (the center of the lintel). There are also different forms of lintels for different types of construction.
Wooden lintels work as a wooden beam would, and in fact, that is exactly what they are. They should be a very large spanning board, or several attached side by side that together span the width of the window. They often bear the load of the wall in secret. Since the structure of wood construction is often entirely covered by the sheathing material (wooden shingles, wood siding, etc.) of the building, wooden lintels are often unseen. Wood trim is usually wrapped around the entire window, hiding the lintel. But oversized wooden beams may be used for lintels, allowing the structural elements to be represented on the exterior. Adobe construction, though not a style of wood construction, also uses large wooden members to both aesthetically and structurally span wall openings. So wooden lintels do not need to be shown, but if so, they should be visibly strong and weight bearing.
Brick lintels have to work as a system, collectively bearing the weight of the wall above them. They may be set out slightly from the wall, and they are usually collectively a single form, different from the system of the wall around them. Brick lintels can come in a number of forms, but soldier courses, stretcher arches and jack arches are the most used. A soldier course is a straight row or multiple rows of bricks turned on end and stacked next to each other. A jack arch is built similar to a soldier course, with its bricks stood on end in a slight arch with a flat base and a nearly flat crown; the bricks are shaved slightly at an angle, to force a slight incline at the ends, and thus the name "arch" applies. A stretcher arch is a grouped set of multiple rows of bricks laid horizontally, with their length in the direction of the length of the wall. Stretcher arches are often nearly horizontal as well, and a solid wooden panel makes up the difference between the top of the horizontal window frame and the bottom of the brick arch.
Stone lintels can either be solid, like wood, or a system, like brick. However, the same rules apply for each condition. If solid, they should run the width of the opening, overlapping slightly at the edges. If a system, they should be broken at appropriate points along the opening. Stone lintels often give an excellent opportunity for ornamentation. Keystones (the angled piece of stone in the center of a stone lintel system) often receive elaborate decoration, accenting their position within the lintel as well as the entire opening in general. Flat single-stone lintels often look stark unless decorated with some carved elements -- swags or garlands, banderol, Greek fretwork, and Vitruvian waves can all accent a lintel beautifully.