---
title: "Brick construction terms: arrises, perpends, lap"
subject: "Concrete Technology and Masonry Structure"
chapter: 7
key: "semester_5/concrete_technology_and_masonry_structure:terms-arrises-perpends-lap"
source: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/terms-arrises-perpends-lap
site: BCT Engineering
---

# Brick construction terms: arrises, perpends, lap

Concrete Technology and Masonry Structure · Chapter 7: Introduction to masonry structures

- Asked in: 2080 Baisakh, 3 marks
- Video: [Technical Terms in Brick Masonry | Brick Masonry | Building Construction](https://www.youtube.com/watch?v=WQNz-Y-fess) — SGK Online Education
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/terms-arrises-perpends-lap
- Whole chapter: https://www.bctengineer.com/md/semester_5/concrete_technology_and_masonry_structure/chapter-7

## Question

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

## Answer

- **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.

```text
 ______ ______ ______
|______|______|______|   perpend = vertical joint
 |__lap__|______|___    lap = overlap between courses
```

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What are arrises?
   A. Sharp edges where two adjacent faces of a brick meet
   B. Vertical joints
   C. Overlap between courses
   D. Bed joints
   Answer: A. In good brickwork arrises are sharp and unbroken. (Key point: Arrises)

2. What are perpends?
   A. Horizontal joints
   B. Vertical cross joints between bricks in a course
   C. Brick edges
   D. Brick faces
   Answer: B. They must not be in line in two successive courses. (Key point: Perpends)

3. What is the lap for good bond?
   A. Full brick length
   B. Zero
   C. One-quarter brick length overlap of a brick over the one below
   D. Half the thickness
   Answer: C. A quarter-brick lap (about 55 mm for a 230 mm brick) is the minimum. (Key point: Lap)

## Related in Concrete Technology and Masonry Structure

- [Brick masonry construction techniques](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Amasonry-construction-techniques) — Concrete Technology and Masonry Structure, chapter 7
- [Single-room wall: brick strength and mortar](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Awall-single-room-8000kg) — Concrete Technology and Masonry Structure, chapter 8
- [Brick and mortar for 230 mm wall (100 kN/m)](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Awall-eccentric-230mm-100kn-5m) — Concrete Technology and Masonry Structure, chapter 8, asked 7×
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