---
title: "Natural bed of stone and its importance"
subject: "Civil Engineering Materials"
chapter: 2
key: "semester_3/civil_engineering_materials:natural-bed-stone-importance"
source: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/natural-bed-stone-importance
site: BCT Engineering
---

# Natural bed of stone and its importance

Civil Engineering Materials · Chapter 2: Building Stones

- Asked in: 2081 Baisakh, 2 marks; 2080 Bhadra, 2 marks; 2074 Chaitra, 2 marks; 2073 Shrawan, 1 marks; 2069 Chaitra, 1 marks; 2071 Chaitra, 1 marks; 2068 Chaitra; 2068 Baisakh (asked 8 times)
- Video: [Part 6 ! Stone ! Natural bed of stone ! Natural bed of stone in arch/cornice/stonemasonry/retaining](https://www.youtube.com/watch?v=OSI3ZGTgXDc) — NARAYANA COACHING CLASSES
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/civil_engineering_materials/natural-bed-stone-importance
- Whole chapter: https://www.bctengineer.com/md/semester_3/civil_engineering_materials/chapter-2

## Question

Define the natural bed of stone and explain its importance.

## Short answer

The natural bed is the bedding plane of stratified rocks. In masonry, stones must be laid with this plane perpendicular to the load for maximum strength and durability; placing it vertically allows water entry and frost scaling. Unstratified rocks like granite have no natural bed.

## Answer

#### Natural bed
In a **stratified (sedimentary or metamorphic) rock**, the layers formed during deposition lie in parallel planes. The plane along which the layers were deposited is the **natural bed** (bedding plane). The stone obtained from the quarry has these layers, and the bed is easily seen as the plane of weakness.

```text
   ______________   <- layers (bedding planes)
  |______________|
  |______________|
  |______________|
```

#### Importance
1. The stone is strongest against loads that act **perpendicular** to the natural bed, and weakest along it, because layers can split or slide.
2. In masonry, stones are laid with their natural bed **perpendicular to the direction of the load**. In arches the bed is placed radial, i.e. normal to the thrust. In cornices and projecting parts the bed is kept vertical.
3. If the bed is placed vertical in a wall, water enters between layers and frost makes the layers flake off (scaling).
4. Identification of bed is therefore necessary during dressing and placing to obtain strength and durability.

Unstratified igneous rocks like granite have no natural bed.

## Check yourself

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

1. What is the natural bed of a stone?
   A. The plane along which layers were deposited in a stratified rock
   B. The flat bottom surface cut at the quarry
   C. The plane at which the stone is dressed
   D. The line along which the stone is split by a chisel
   Answer: A. In stratified rocks the layers were laid in parallel planes; that plane is the natural bed and is a plane of weakness. (Key point: Definition of natural bed)

2. In ordinary masonry, how should the natural bed be placed relative to the load?
   A. Parallel to the direction of load
   B. Perpendicular to the direction of load
   C. Vertical in all cases
   D. At random
   Answer: B. The stone is strongest for loads acting perpendicular to the bed, so beds are kept perpendicular to the load. (Key point: Placing in masonry)

3. Why is a vertically placed bed in a wall harmful?
   A. The stone becomes too heavy
   B. The stone cannot be dressed
   C. Water enters between layers and frost makes them flake
   D. The mortar will not set
   Answer: C. Water seeping between layers freezes and causes scaling of the layers. (Key point: Vertical bed danger)

4. Which rock has no natural bed?
   A. Sandstone
   B. Slate
   C. Limestone
   D. Unstratified igneous rock such as granite
   Answer: D. Only unstratified igneous rocks like granite lack layers and so have no bed. (Key point: Igneous rocks)

## Related in Civil Engineering Materials

- [Why and where stone is preferred](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Astone-preferred-engineering) — Civil Engineering Materials, chapter 2, asked 3×