A blind arch is an arch-shaped opening within a structure that has been filled in, making it unusable as a traditional door or window. This architectural element features heavily in Gothic and Romanesque Revival designs, and is typically constructed from masonry or stone. A blind arch may be filled in immediately after construction, allowing it to serve as a primarily aesthetic function from the very beginning. In other cases, these arches are originally designed to function as access points, but later filled in for a variety of reasons. When used in a series, blind arches form a feature known as a blind arcade or Lombard band.
The exact design of a blind arch can vary based on when and where it was created. Many feature a rounded top positioned above a standard door or window-sized opening. Some arches may also be more ornate, with a pointed or peaked top, particularly in Middle Eastern architecture. The outline of the arch is often very pronounced, particularly when built as an original aesthetic feature.
Regardless of when a blind arch is infilled, the wall thickness of the filled section may match or differ from the surrounding wall thickness. Often, this filled area is made from the same material as the surrounding wall, and thus virtually flush with the area outside of the arch. When the area is filled in later, or if builders want to add depth and shadow to the facade, they may use a thinner infill than the surrounding wall thickness. The area within a blind arch may also be thicker, especially if the arch has been filled for security, or to preserve a crumbling structure.
Blind arches may take the form of a standard door or window, or simply be built into the wall for decoration. They are often combined with functional archways, which permit access into a building or hold stained glass windows. While a blind arch can be used both indoors and out, it's most common on exterior walls of a building. These arches were sometimes use as decorative elements in medieval structures. Older buildings with open arched windows may be infilled later to increase security or to keep rain and other elements out.
In traditional Gothic or Islamic design, the blind arch was often covered with a decorative feature known as tracery. Tracery consists of bands of material arranged over a blind arch, window, or simply within an opening to form a design. These bands feature intricate designs, including swirls and classic patterns like clovers and other traditional shapes.