In today’s construction landscape, aesthetics often take center stage, sometimes at the expense of structural integrity. A prime example of this is the increasing use of ‘skinny’ columns in buildings, particularly in areas prone to natural disasters like Bali. While these columns might offer a clean, modern look by blending seamlessly into walls, they pose significant structural risks that homeowners and builders need to understand.
Understanding Structural Columns
Structural columns are the backbone of any building. These vertical, reinforced concrete structures transfer the weight of walls, floors, and roofs down to the foundation. Combined with reinforced concrete beams, they create a strong frame that is designed to withstand various forces including strong winds, earthquakes, and ground subsidence. Traditionally, columns in houses have been square, typically measuring 20 cm by 20 cm, providing equal strength in all directions. However, modern design trends favor rectangular columns that are wider but much thinner, often around 15 cm thick by 30 cm wide, so they can be hidden within walls.
The Problem with ‘Skinny’ Columns
The move towards thinner columns raises several structural concerns:
- Reduced Strength: While a skinny column might have adequate strength along the wall (direction A), it is considerably weaker at right angles to the wall (direction B). This is because the column’s strength is determined by the size and spacing of the steel bars within the concrete. In a square column, steel bars are placed further apart, providing more resistance to bending. However, in a rectangular column, the bars are closer together, reducing the column’s overall strength.
- Steel Bar Protection: Concrete provides a protective layer to prevent steel from rusting. A minimum of 6 cm of concrete cover is recommended, especially within 50 km of the sea due to salt in the air. With a 15 cm thick column, achieving this level of protection becomes impossible, leaving only about 3 cm for the two layers of steel. This inadequate cover allows oxygen to penetrate and oxidize the reinforcing steel.
- Construction Challenges: Pouring concrete into thin formwork is much more difficult. The concrete needs to be vibrated to ensure proper filling and elimination of air gaps. This process is challenging with square columns and becomes even more difficult in 15 cm thick columns, often resulting in poorly constructed columns.
Why Square Columns Are Still the Best
To ensure the safety of your building, particularly in earthquake-prone areas, using square columns remains the best option. Square columns offer equal strength in all directions and allow for better protection of the steel reinforcing bars, while enabling more successful concrete casting and vibration processes. If clean building lines are still desired, consider constructing the walls so that the inner surface of the walls is level with the inner surface of the columns, allowing the columns to be placed on the outer surfaces of the walls.
Conclusion
While the aesthetic appeal of ‘skinny’ columns is undeniable, it is important to prioritize safety and structural integrity when building or renovating. Understanding the engineering behind reinforced concrete design is crucial in making informed decisions about the construction of your home. Always ensure that your building adheres to sound structural engineering principles and standards, particularly when building in areas prone to natural disasters. By using well-designed square columns you are ensuring a safer structure for the future.
