wythe
A continuous vertical section of masonry, one unit in thickness.
wythe: one brick-thick column of masonry
A wythe is a single-width vertical run of masonry units, typically one unit thick. In brick construction, this means a column of bricks laid so that their long faces run horizontally, creating a wall section that is roughly 4 inches thick (the width of a standard brick). The term applies equally to concrete blocks, stone, or other masonry units stacked vertically and bonded with mortar.
Multi-wythe walls are built by laying two or more wythes side by side and bonding them together with ties, header courses, or collar joint filling. A standard two-wythe brick wall is 8 inches thick; three wythes make a 12-inch wall. This modular approach lets masons build to different thicknesses and strengths without changing the individual unit size. The space between wythes, called a collar joint, may be left hollow for air circulation or filled with mortar or insulation.
Why the term matters in practice
Specifying walls by wythe count is clearer than wall thickness alone because brick and block sizes vary regionally and over time. A two-wythe wall is understood instantly by any mason, regardless of the exact mortar joint width or unit dimensions. Bond patterns, flashing installation, and tie spacing all depend on knowing wythe count. Structural engineers also think in wythes when calculating load capacity and lateral bracing of masonry.
Problems arise when wythes are not properly bonded or when movement joints between wythes are sealed instead of left as drains. Water trapped in collar joints can freeze and spall the outer wythe in cold climates. Insufficient header courses or ties can cause outer wythes to buckle independently of inner wythes, especially in tall walls exposed to wind or earthquakes.
The word itself comes from Old English and appears in masonry literature by the 18th century, though its exact origin is disputed. It remains the standard term in building codes and specifications across North America and the UK, making it essential vocabulary for anyone reading construction documents or working in brick and stone trades.