CHAPTER ONE
INTRODUCTION
1.1  Background of the study
Modern building of engineering structure are complex and require Architect, structural engineers, quantity surveyor, good contractor and supervisors for detailed planning, safe design and efficient use of appropriate material. When these requirement are not made adequately, failure becomes more probable? According to Evelyn (September – 2004) cracks in building elements may constitute a defect in a variety of ways. In many cases a particular crack occurrence may result in more than one type of defect. A serviceability defect and an appearance defect. And according to Shri M.M Goyal (2004) occurrence of various crack patterns in the building during construction and after completion, when it is subjected to super imposed loads and during service life, is a common phenomenon. A building component develops cracks whenever the stress in the components exceeds its strength. Stress in the building components caused by external applied forces, such as dead, live, wind or seismic leads, foundation settlement e.tc or it could be induced internally due to thermal movements, moisture changes, elastic deformation, chemical action e.t.c
The occupants of buildings may served as good tenants or occupants, Since their knowledge of the facility in many ways have contributed in checking failure and defects in residential buildings. It is important for the tenants to understand the causes of cracks in structures e.g.
Non structural cracks – these are mostly due to internally induced stresses in building material and do not endanger safety of a building but may look unsightly. Or may create an impression of faulty work or may site a feeling of insatiability. In some situation due to penetration of moisture through them, non structural cracks may spoil the internal finishes thus adding to the cost of maintenance or corrode the reinforcement, thereby adversely affecting the stability of the structure in long run, e.g vertical crack in a long compound wall due to shrinkage or thermal movement.
Cracks may appreciably vary in width from very thin hair crack barely visible to naked eye to sapling crack. Depending upon the crack width cracks are classified as: thin crack – less than 1 mm in width, medium crack- 1 to 2mm in width, wide crack – more than 2mm in width and crazing – occurrence of closely spaced line cracks at the surface of a structure or material.
The cracks that occur are of uniform width some are narrow at one end gradually widening at the other, the above pattern of cracks usually occur on the surface of plaster or rendering of the structure of building, and those patterns some occur on the walls of the building such as; straight, toothed, stepped or map pattern. The random type crack may be vertically or horizontally or diagonally e.t.c
Therefore, there is need for the occupants of the residential buildings to periodically examine and critically assess the stability and ability of the structure of their buildings.