Minimum thickness of stiffening wall for 1 to 3 storeys shall not be less than:
🔬 Understanding Stiffening Walls
A stiffening wall, also known as a cross wall, buttress, or pier, is a wall built at an angle (usually 90°) to a longer, main wall. Its primary purpose is not necessarily to carry vertical loads, but to provide lateral support to the main wall. This support prevents the main wall from buckling or bending under its own weight or from lateral forces like wind.
Function: The stiffening wall effectively reduces the unsupported length of the main wall, which in turn reduces its slenderness ratio and increases its stability and load-carrying capacity. The question asks for the minimum required thickness for such a wall in low-rise construction (1 to 3 storeys).
⚖️ Detailed Analysis of the Requirement
Building codes, such as the National Building Code (NBC) of India, provide guidelines for the minimum thickness of masonry walls to ensure structural safety and stability.
(a) 10 cm
Why it's correct: For low-rise buildings (typically up to 3 storeys), building codes often permit the use of a half-brick wall as a stiffening wall or an internal partition wall. The nominal thickness of a half-brick modular wall is 10 cm (9 cm brick + 1 cm mortar). This thickness is considered sufficient to provide the necessary lateral bracing for the main walls in such structures without needing to be a full load-bearing wall itself.
(b) 15 cm
Why it's incorrect: While a 15 cm thick wall (often built with special blocks or as a one-brick wall with traditional bricks) would certainly be strong enough, it is not the specified *minimum* thickness. The codes allow for a thinner, 10 cm wall.
(c) 20 cm & (d) 30 cm
Why they're incorrect: These represent one-brick (20 cm) and one-and-a-half-brick (30 cm) walls, respectively. These are major load-bearing wall thicknesses and are far greater than the minimum requirement for a simple stiffening wall in a low-rise building.
💡 Study Tips for Masonry Dimensions
- Stiffening Wall = Bracing Wall: Think of a stiffening wall as a "brace" for a longer wall. It doesn't need to be as thick as the main load-bearing walls.
- Half-Brick is the Minimum: Remember that the absolute minimum thickness for a stable masonry wall is generally a half-brick wall. For a modular brick, this corresponds to a nominal thickness of 10 cm.
- Know Your Wall Thicknesses:
- 10 cm: Half-brick wall (partitions, stiffening walls).
- 20 cm: One-brick wall (main load-bearing walls).
- 30 cm: One-and-a-half-brick wall (thicker load-bearing walls).