Damp Proofing Course

Damp Proofing in Buildings: Comprehensive Guide

Introduction to Damp Proofing Course (DPC)

Damp proofing is an essential aspect of construction that prevents moisture ingress into buildings, ensuring durability and structural integrity. The Damp Proof Course (DPC) is a protective barrier applied to walls, floors, and roofs to resist moisture penetration.

Defects of Dampness in Buildings

• Structural Weakening: Continuous moisture exposure weakens building materials like bricks, concrete, and timber.
• Efflorescence: White salt deposits on walls due to moisture migration.
• Peeling Paint and Plaster Damage: Damp walls lead to flaking paint and disintegrating plaster.
• Mold Growth: Damp conditions encourage mold and fungi, leading to health risks.
• Corrosion of Metals: Moisture accelerates rusting of reinforcement bars and metal fixtures.
• Electrical Hazards: Increased conductivity of wet surfaces can cause short circuits.

Causes of Dampness

• Poor Drainage System: Inefficient water disposal leads to moisture accumulation.
• Capillary Rise of Moisture: Water rises through porous building materials due to surface tension.
• Leakage from Roof and Walls: Poor roofing and inadequate wall protection allow water ingress.
• Condensation: Internal moisture due to temperature differences results in damp patches.
• Improper Construction Techniques: Inadequate mortar joints and improper materials contribute to dampness.

Sources of Dampness in Buildings

• Groundwater: Moisture rising from soil into walls and floors.
• Rainwater Penetration: Through walls, roofs, and parapets due to cracks.
• Leakage from Plumbing: Faulty pipes and drainage systems.
• Humid Climate Conditions: High atmospheric moisture leading to condensation.

Methods of Damp Proofing

• Membrane Damp Proofing: Using sheets of bitumen, mastic asphalt, or polythene.
• Integral Damp Proofing: Adding waterproofing compounds to concrete mix.
• Surface Treatment: Applying water-repellent coatings like silicone-based solutions.
• Cavity Wall Construction: Leaving a cavity between two walls to prevent moisture penetration.
• Pressure Grouting: Injecting cement slurry into cracks to seal moisture paths.

Selection of Materials for DPC

• Bituminous Felt: A flexible sheet that prevents moisture migration.
• Mastic Asphalt: Impermeable and long-lasting.
• Cement Concrete: Strong and durable when mixed with waterproofing compounds.
• Metal Sheets: Lead, copper, and aluminum sheets used in special cases.

Damp Proofing Treatment in Buildings

• Foundations: Providing horizontal and vertical DPC at plinth level.
• Floors: Laying waterproof membranes or concrete layers.
• Walls: Applying surface coatings or cavity walls.
• Flat Roofs: Using bituminous felt, mastic asphalt, or special coatings.
• Parapet Walls: Sealing tops and using coping stones.
• Multi-storeyed Buildings: Waterproof coatings and advanced membrane systems.
• Pitched Roofs: Using underlays and flashing at joints.

Specification for Laying 38 mm Thick DPC with Cement Concrete 1:2:4 at Plinth Level

1. Preparation of Surface: Cleaning and leveling the plinth surface.
2. Mixing Concrete: Using a ratio of 1:2:4 (cement: sand: coarse aggregate).
3. Laying the Concrete: Spreading the mix uniformly over the plinth.
4. Compaction and Curing: Ensuring proper compaction and curing for at least 7 days.
5. Application of Waterproofing Compound: Enhancing moisture resistance.
6. Final Finishing: Smoothing and ensuring proper joint sealing.

Conclusion

Damp proofing is a critical element of construction that ensures the longevity and safety of buildings. By understanding the causes, sources, and methods of damp proofing, builders can implement effective treatments for long-lasting structures.