Understanding the Importance of Damp Proofing in Construction

Dampness, the infiltration and spread of moisture within a building, is a common problem that can weaken the structure and jeopardize the health of its occupants. Dampness can enter through walls, floors, roofs, or other openings, making it crucial to implement preventive measures during construction. These measures are collectively known as damp proofing.

Sources of Dampness:

• Construction Defects: Improper drainage planning, faulty pipe fittings, unsealed construction joints, and inadequate roof slopes can all contribute to dampness.
• Condensation: Atmospheric moisture that condenses on walls and ceilings can lead to dampness issues.
• Ground Moisture: Foundation and floor materials can absorb moisture from the ground, which then rises through capillary action.
• Rain Splash: Accumulated rainwater can seep into walls.
• Exposed Parapet Tops: Lack of proper damp proofing on parapet tops can allow moisture to enter.

Detrimental Effects of Dampness:

Dampness can have a devastating impact on a building and its occupants:

• Aesthetic Damage: Rough patches and crumbling plaster on walls and ceilings.
• Structural Deterioration: Metal components corrode, electrical fittings malfunction, woodwork decays, and decorative materials like paint and wallpaper are damaged.
• Material Degradation: Stones, bricks, and tiles deteriorate due to efflorescence (a white, salty substance) caused by water penetration.
• Health Hazards: Dampness fosters the breeding of mosquitoes, termites, and disease-carrying germs, potentially causing respiratory problems and other illnesses.

Damp Proofing Materials:

Various materials can be used for damp proofing, categorized as:

• Flexible: Bituminous materials, plastic sheets, metal sheets (copper, lead).
• Semi-Rigid: Mastic asphalt.
• Rigid: Impervious bricks, stones, slates, cement mortar, or bitumen-painted cement concrete.

Additionally, mortar and cement concrete with damp-proofing compounds, coarse sand layers, and continuous plastic sheets under floors can be employed.

Principles of Damp Proofing:

Several key principles guide effective damp proofing:

• Concealment: Damp-proofing courses should not be left exposed on the wall surface.
• Overlap: When using sheets or mastic asphalt, ensure a minimum 100 mm overlap.
• Continuity: Maintain continuous damp-proofing at joints and corners.
• Level Surface: Prepare a level mortar bed for laying the damp-proof course.
• Junction Sealing: Cover vertical and horizontal junctions with a cement mortar fillet of about 75 mm.

Methods of Damp Proofing:

Different treatments are applied to various parts of the building:

• Foundations: Construct an air drain parallel to the wall for protection, along with horizontal and vertical damp-proof courses. Cover the drain with an RCC slab and install gratings.
• Floors: Lay a 75-100 mm thick layer of coarse sand under the flooring. If the soil is wet, use a membrane DPCbefore laying bricks and flooring.
• Walls: Protect walls at the plinth level (at least 150 mm, ideally 450 mm above ground level) and the parapet top with capping over DPC on a concrete bed.

By understanding the causes and consequences of dampness and implementing appropriate damp-proofing measures, you can create a dry, healthy, and structurally sound building that withstands the test of time. Remember, damp proofing is not just about preventing immediate damage; it's an investment in the long-term well-being of your property and its occupants.