Dampness in a building may occur due to faulty construction, the use of poor-quality building materials or bad architectural design. Dampness affects the lifespan of a building or structure, but it also creates unhygienic conditions. Mold and fungi love to grow in damp conditions, so it is best to fix any signs of wet concrete as soon as possible.
The measures taken to prevent water from leaking into a roof is usually called waterproofing. The treatment given to a structure to keep its basement, floor and walls dry is called damp proofing. Some of the problems caused by dampness in a building include the disintegration of bricks, stones, tiles; the softening and crumbling of plaster; the corrosion of metals; the warping, buckling and rotting of timber; the presence of termites; deterioration to electrical fittings and the bleaching and flaking of paint with the formation of coloured patches.
What causes dampness in a building?
The absorption of moisture by building materials is one of the main causes of dampness. This can be caused by faulty structure design, bad workmanship or the use of defective structures or materials.
Sources of dampness in buildings include the rising of moisture through the foundation walling; splashing rainwater which rebounds after hitting the wall surface; penetration of rainwater through unprotected tops of walls, parapets or compound walls; gutters which allow rainwater to descend through the top supporting wall. In the case of buildings with flat roofs, inadequate roof slopes, improper rainwater pipe connections and defective junctions between roof slabs and parapet walls can also cause dampness.
How to prevent dampness in a building
1. Membrane Damp Proofing
This involves placing layers of water-repellant materials between the source of dampness and the structure. This type of material is commonly known as damp proof course (DPC). It could be made from materials like plastic or polythene sheets, cement-based concrete, bituminous felts or asphalt. Applying DPC in a basement is usually referred to as tanking and can prevent ground moisture from seeping into the concrete walls.
2. Integral Damp Proofing
This form of damp proofing involves adding certain waterproofing compounds to the concrete mix to increase its impermeability (resistance to absorbing moisture). The compounds made from sand, clay or lime help to fill the voids in concrete and make it waterproof. Compounds such as aluminium sulfate, calcium chlorides and alkaline silicates chemically react when mixed with concrete, producing waterproof concrete.
3. Surface Treatment
This type of treatment involves filling up the pores of the surfaces subjected to dampness. Water repellent metallic soaps such as calcium and aluminium oleates and stearates are often used for this purpose. Cement coating, transparent coatings, paints, varnishes and bituminous solutions also fall under this category. Another economical option for damp surface treatment is lime cement plaster. This effectively prevents dampness in walls as a result of rain.
For this type of damp-proofing, a cement gun machine is used to deposit a layer of rich cement mortar over the surface. The surface must be completely cleaned of dirt, dust, grease or loose particles by wetting it properly. Cement and sand (or fine aggregates) are then fed into the machine. This mixture is finally shot onto the prepared surface under a pressure of 2 to 3 kg per square centimetre by holding the nozzle of the cement gun at a distance of 75 to 90 cm from the working surface.
5. Cavity Wall Construction
This form of damp-proofing consists of protecting the main wall of a building by an outer wall, leaving a cavity between the two walls. The cavity prevents moisture from spreading from the outer to the inner wall.
These five methods of damp-proofing will help to protect concrete structures from excess moisture, which can lead to mold, fungus, rot and damage to buildings. Contractors and homeowners must always inspect their buildings for any signs of stress and damage, such as dampness, which could affect the integrity and durability of the structure.
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