An occurrence of the cracks is often a subject that raises numerous questions. Cracks may appear in structures, either at the initial stage or with time. It should first of all be accepted that cracks of some type are unavoidable in any structure.
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Occurrence of various crack patterns in the building mostly takes place during construction and/or after completion. A building component develops cracks whenever the stress in the components exceeds its strength. Stress in the building component is caused by externally applied forces/loads. Occurring of cracks after completion or during the service life may be due to additional super imposed loads (any applied load other than self weight of structural element) than considered while designing, is a common phenomenon.
The commonly used building material namely masonry, concrete, mortar etc. are weak in tension and shear. Consequently the stresses of even small magnitude causing tension and shear stresses can lead to cracking. Internal stresses are induced in the building components on account of thermal movements, moisture change, creep, elastic deformation, Corrosion in reinforcement, chemical reactions, poor construction practices, poor structural design and their specification, wrong selection of material, poor maintenance, quality of materials etc.
All these above described phenomenon causes dimensional changes in the building components. If Dimensional changes movement is restrained then stresses are induced and whenever these stresses (tensile or shear) exceed the strength of material, cracking occurs.
Generally, movement is restrained due to following reasons,
01. Inter connectivity of various members
02. Resistance between the different layers of the components
To sum up care should be taken while constructing your house and also even after construction is complete. Periodical inspection and maintenance should also carried out.