In stone masonry, if stones are so placed that their layers are parallel to the direction of load, they
📖 Understanding the "Natural Bed" of a Stone
Many stones, especially sedimentary rocks like sandstone and limestone, are formed in layers over millions of years. These layers are called bedding planes or the "natural bed" of the stone. Think of them like the pages of a book—it's easy to separate the pages, but very difficult to rip the book in half across the pages.
In masonry, the "direction of load" is almost always the vertical force of gravity pushing down on the wall. The fundamental rule of stone masonry is to place stones so their natural bed is perpendicular to this load, ensuring maximum strength.
🔬 Detailed Analysis of Incorrect Placement
The question describes placing the stone so its layers are parallel to the direction of the load. This means the layers are standing vertically, like a book placed upright on a shelf. This is incorrect and dangerous for two main reasons.
C. Both (a) and (b)
This is the correct answer because both issues—splitting and moisture damage—are direct consequences of placing the stone on its edge instead of its natural bed.
A. They split easily
When the layers are vertical, the downward pressure from the wall above acts to separate these weak planes. The load tries to push the layers apart, causing the stone to flake or split. The stone has very little strength in this orientation.
B. They are affected by moisture
When the layers are vertical, their edges are exposed to the weather. Rainwater can easily penetrate these openings. In colder climates, this water freezes, expands, and acts like a wedge, forcing the layers apart (a process called frost wedging). This leads to rapid decay and deterioration of the stone's face.
📊 Summary: Stone Placement in Masonry
| Placement | Description | Consequence | Verdict |
|---|---|---|---|
| Correct | Layers are perpendicular to the load (horizontal). | Maximum strength; moisture runs off the surface. | Required |
| Incorrect | Layers are parallel to the load (vertical). | Stone can split; moisture penetrates easily. | Unsafe |
💡 Study Tips
- The Book Analogy: A book is strongest when you press down on its cover (load perpendicular to pages). It's weakest if you stand it on its end and press down (load parallel to pages)—it will just splay open. Stones work the same way.
- Load Follows Gravity: Remember that the primary load in a wall is always downwards due to gravity.
- Perpendicular is Perfect: The perfect way to place a stone is with its natural bed perpendicular to the force of gravity.