Causes of cracks in Buildings
In the previous article, we discussed the occurrence of cracks in buildings due to climatic factors and cracks occurred due to problem at the time of construction of the building. These fall under the category of Minor causes of Cracks in Buildings.
Now we will go ahead with our discussion on “Major causes of Cracks in a Building”.
Major causes of cracks in a building
- Movements of the ground
- Over loading
- Effect of gases, liquids and solids
- Effect of changes of temperature
- General causes such as vibrations etc
Movements of the ground
Mining subsidence, land slips, earthquakes, moisture changes due to clay shrinkable soils (for example, Black cotton soil).
Cracks occur because a part of the building is displaced from the rest without any change in the actual size of the material.
- Overloading of the ground
- Overloading of the building itself
- Overloading of the building parts result in cracks
For example; Cracks under a floor due to overloading of slab.
Overloading forced may be due to
- External (excessive wind/snow loads)
- Internal (from heavy machinery etc.)
Effect of Gases, Liquids and Solids
- Only gas likely to produce cracks is carbon dioxide (CO2).
- Causes carbonation of porous cement products
- Leads into an overall shrinkage showing crazing cracks
- Water is the most commonly used liquid when not taken care of can prove hazardous for the structures.
- Construction water i.e., that is utilization of water during the construction process
- Water in the usage of the building
Effects of water
- Physical (i.e. due to change in water content)
- Chemical (directly or indirectly affecting other materials)
For example, Volumetric increase due to chemical changes or Steel corrosion, sulphate attack with water.
Soluble sulphates are most common and are found in various materials and soil.
They are a great cause of concern. They attack the cement products which in turn result in the deterioration of the structure.
Effect of changes in Temperature
Various building materials are used for the construction of a building and all the materials have different coefficient of expansion. Due to changes in the temperature, the expansion and contraction of the building components takes place which result in the changes in the size and shape of the components.
Smaller buildings are less affected.
In larger buildings, the change in size of one part causes cracks although not in expanded part.
For example; Crack below the slab/beam in RCC frame Brick pin buildings. These cracks can close up completely as a result of changes of temperature.
Vibrations cause cracks in buildings only when their amplitude of vibrations is high.
Apart from vibrations caused due to earthquakes, the vibrations caused due to heavy machinery, traffic, sonic booms are also responsible for the occurrence of cracks in buildings.