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Defects occur in building for a variety of reasons. This is perhaps not surprising when one considers the wide range of materials and techniques used in the construction of building, differences in condition on building sites and the varied occupational uses of the completed building. The defects in buildings occur because the inadequate or drawback of the original design, the building was constructed without according with the design or with appropriate practise, or the workmanship was below standard, or because the building has been accepted forces. The emergence of defects will affecting the comfort of occupants, such as noise interruption, solar gain and glare, have however been omitted as it is considered that they do not affect the fabric or the services and are not therefore building defects but purely defects of design.
Besides, most of the defects can be occur due to the designer did not fully appreciate that the changes can befall in the construction or in the materials used, therefore the designer did not provided adequate safeguards in his design. If the chosen materials are unsuitable for the conditions, the materials will consider as defects. Most of the times, designer will take into account the cost to determine the choice of materials. It is important to understanding of the inherent properties of materials before select any materials. Before making the choices of materials for the construction, the designer must understand of the inherent properties of those materials. Greater use of the concept of "trouble-shooting in advance" can improved the designs and will undeniably lead to a reduction in the defects which occur in buildings.
Dampness is one of the defects which are most difficult to trace and diagnose. The dampness only can be perceived once it appears at the surface of the walls. There are countless ways in which water can exist in a building. Dampness may occur in the same building and at the same time even be responsible for the same damp patch. Buildings are assembled by a lot of different materials. All the materials have different inherent properties and many of them are water-absorbent. There are the major sources of water caused the dampness in building, such as construction water, intruding water, condensation and occupational (Eldridge, 1976).
In the construction of a building, a great quantity of water is required. A great quantity of water is required in the construction of a building, even for an ordinary building at least several tons of water is necessary. As well as some of the water will be used in setting the materials such as Portland cement, gypsum plasters and etc. Some construction water may be dried up at the time before the buildings have been occupied, but some construction water will still be retained in the building's structure. Even though heating will dry up the water inside the structure, but in some case the water inside the structure are failed to dry up due to the walls have been applied the impervious decorations such as paintwork. And finally, the construction water will kept accumulate inside the walls (Eldridge, 1976).
Rainfall is one of the reasons to allow the water into a building. While rain falls by gravity but it can be blown by the wind in all directions against a building. The driving rain will find any weakness on the wall and into a building either directly through the defects of the walls or indirectly by absorption. The water may transfer through the defects on the walls such as cracks or hollow sections for some distance and wet the internal surface of walls. Therefore, this would be very difficult to find the points of water entry. Besides, dampness may be enter a building from ground even the properly constructed of damp-proof course or membrane have been carry out. The watertightness of the joints is very important in the prevention of rain penetration. Intruding dampness which wets insulating materials may seriously lower their effectiveness and lead to condensation. The intruding dampness can be divided into penetration damp and rising damp (Eldridge, 1976).
Penetrating damp is caused by the porous nature of the building and as a result of external water getting into a building through the external walls and ultimately affects the internal wall surfaces. Besides that, the buildings near coastal areas or areas facing the sea can also suffer from penetrating damp. The penetrating damp of the walls will caused serious deteriorating affects to the internal finishing like damp staining, salting, blown plaster, spoiling and peeling of the wall finishes.
Wall penetrating dampness occurs in a building are related with the somewhat faulty building work or the fault in the plumbing work which has allowed water to enter into the building. The common defects that can result in the transfer of water from the external façade of a building into its living accommodation such as the defective of roof coverings, poorly maintained walls, poorly guttering and down pipes, poorly fitting or rotten door and windows frames, broken render or damaged pointing. Even these defects can be cured, but the affects of residual moisture within the building can continue to create problems for months and sometimes years. On the other hand, a watermark may be appearing on the internal wall and it will grow if the water continues to enter thus penetrating damp walls. In addition, the watermark will grow rapidly and become worse especially after the heavy rainfall. (David Sutcliffe, n.d.)
Rising damp usually occurs in the older brickwork which the brickwork or the mortar between the brickwork is more porous. The mortar in the older buildings will losing its original adhesive properties, becomes soft and crumbles easily, almost reverting back to a sandy base, therefore the mortar will becomes absorbent and pass water through it. In other word, the rising damp is hardly occurs in the newer brickwork where the brick and cement mortar courses are in good condition. Besides that, the rising damp also may occur in the brickwork due to not providing the damp proof course or where the damp proof course has failed.
The rising damp can be occur in the brick walls due to the water upward movement through the porous mortar from the ground salt (Chloride & Nitrates), this action as known as Capillary Action. Once the rising moisture is above the floor level, the water evaporates and leaves the salt deposits behind. The evaporation often draws more water up and in turn leaves more salts behind. The longer the moisture is allowed to rise, the more salts will become evident.
Water vapour is normally present in the air. The quantity of water vapour contained depends on the temperature of the air. This ratio is called the 'relative humidity'. Hot air is able to carry much more water vapour than cold air, so as the temperature of air increase, it is able to hole a greater volume of water vapour. Such water vapour comes from our breathing, bathing, cooking and other domestic activities. When the water vapour contact with cold surface it will converted into liquid water. The temperature of the surface at which the water vapours condensate is called the 'dew point'. The condensed water may appear on any of the internal surfaces of the building or form within the construction and known as "interstitial condensation". The condensed water may through a crack on the wall to appear possibly on the internal surface of wall even some distance from its points of origin. Therefore, this form of condensation can be very knotty due to the difficulty in identifying and its adverse effect on the insulation. Besides, it also damaging and give rise to other defects to the walls such as the materials used in the walls especially in cavities and voids. Moreover, the condensation is most lightly to occur especially in locations where the relative humidity of the internal air is high such as bathrooms and kitchens. Some of the materials have the property of absorbing moisture from the air. The amount of water condenses in walls is very considerable indeed, because it is not only damage the fabric of a wall and lead to more frequent redecorating, but it is also may leading the wall to a state of almost permanent dampness and providing suitable conditions for the growth of mould and mildew. The growth of mould and mildew will affect the health of the building's occupants.
For a variety of reasons the maintenance of the internal decorations is carried out at reasonably short intervals and this often conceals the consequential effects caused by the defects and therefore the symptoms of defects in the underlying fabric or in other related parts of a building. However, this may cause to take more time to discovery of a defect or camouflage its seriousness if the defects were found.
Most of the defects concern either the plaster applied to the walls or the decorations. In addition the finishes such as timber paneling and decorative faced boards are unlikelihood to defects except the possible opening of the joints between the boards.
Most of the cracks in the plasterboard will usually have their origin in the sub-strate. By inserting a thin and stiffish piece of wire in to the crack in the plaster can make sure whether the crack have it origin in the sub-strate and it is also a efficient way to measuring the distance penetrated of the crack.
The decoration on the inner face of the external walls is likely to be damaged by the moisture. On the other word, moisture damage to the decoration on the partition walls is less probable because the surface of partitions will usually be warmer and therefore less vulnerable to condensation.
If the ground salts (Chloride & Nitrates) have accumulated in the wall over a long period and have been transferred into the plaster it will brought deteriorative effect for the finishes of the walls. This because the ground salts have the property of absorbing moisture from the air and influence the plasterwork damp.
One of the problems with internal walls is ascertaining the form of construction and the materials used. If they are of solid construction it may often be possible to drill a small hole at some convenient point to find out what material has been used, but this information is accurate only if it can be assured that the same material has been used for the whole wall.