Get Your House Right: Lintels

By Marianne Cusato and Richard Sammons

Openings in masonry walls may be spanned in two manners: lintels or arches. Lintels, depending on the material, are most economically used for shorter spans. Arches, because they are in compression and not subject to bending or shear stresses, can span further. The visual expectation for the size of the lintel is based on what was traditionally possible in masonry construction, without hidden structure.

In Figure 1, the thin lintel is disturbing because, logically, it could not support the weight of the wall above; and, although not structurally flawed, the overhang is excessive. The lintel in Figure 2 is both thicker than necessary for the span and does not have any overhang or bearing. Were it not for hidden support, this lintel would slide into the void below like a guillotine.

Figure 3 shows a reasonable lintel. The height, to the nearest brick course, is approximately 1/6 the width of the opening. This can also be calculated by doubling the span in feet, and converting it to inches, i.e. a 3-inch span would have a 6-inch lintel, (but for practical purposes, this would probably be increased to 8 inches to align with the next brick course). The overhang of the lintel in the wall is a minimum of 4 inches, or 1/2 the height of the lintel, whichever is greater.

Figure 1.

Figure 2.

Figure 3.

Marianne Cusato and Richard Sammons are architects with Fairfax & Sammons Architects in New York.  They are co-authoring "Get Your House Right, A Builders Guide to Avoiding Common Mistakes in Traditional Architecture" with Léon Krier, which will include a compilation of drawings addressing many of the typical mistakes made when designing, detailing and building traditional architecture.