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Brick construction terms: arrises, perpends, lap

Short answer

Arrises are the sharp edges where two brick faces meet. Perpends are the vertical joints between bricks in a course; they should not align in successive courses. Lap is the horizontal overlap of a brick over the one below, typically at least quarter-brick length (about 57 mm) for good bond.

Define the following terms used in brick construction technology: Arrises, Perpends and Lap.

  • Arrises: the sharp straight edges formed where two adjacent faces of a brick meet. In good brickwork the arrises must be sharp and unbroken.
  • Perpends: the vertical (cross) joints between bricks in a course. In a good bond the perpends of alternate courses lie in one vertical line, but those of two successive courses never do.
  • Lap: the horizontal distance by which a brick in one course overlaps the brick below it, measured along the length of the wall. For a good bond the lap should be not less than one-quarter of the brick length (a quarter-brick lap, about 57 mm for a 230 mm brick), as in English bond.
 ______ ______ ______
|______|______|______|   perpend = vertical joint
 |__lap__|______|___    lap = overlap between courses

✓ Answer checked by Claude Opus 5.5 (high effort)

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