Damp Proof Course (DPC) is a barrier provided in buildings to prevent moisture from rising through walls and floors. It is essential in construction to block ground moisture that can cause damage to plaster, paint, reinforcement, wood, and even the structural integrity of a building. Knowing what is damp proof course (DPC) helps homeowners, builders, and engineers ensure long-lasting, healthy, and moisture-free structures. DPC is usually installed at plinth level in the form of a horizontal layer made from waterproof materials like bitumen, plastic membranes, cement mortar, or chemical coatings. It ensures that water from the ground does not seep upward into the structure by capillary action.
Why is Damp Proof Course Important?
The primary reason DPC is important is to protect the structure from rising dampness. Without it, buildings can suffer from peeling paint, mold growth, corroded reinforcement, rotten timber, and poor indoor air quality. DPC enhances durability, reduces maintenance costs, and protects interiors and finishes. It keeps moisture at bay and ensures the structure remains safe, dry, and aesthetically appealing.
How Dampness Affects Buildings
Moisture is one of the biggest enemies of construction. Dampness can reduce the strength of walls, weaken plaster, corrode steel reinforcement, and damage electrical wiring. It also leads to health hazards due to mold and mildew growth. Over time, dampness degrades the look and performance of buildings and results in frequent repairs and higher maintenance costs.
Types of Damp Proof Course (DPC)
Flexible DPC
Made from flexible materials that can accommodate slight movement or settlement. Common options include bituminous sheets, plastic membranes (polythene), and rubber-based sheets. These are popular in modern construction due to ease of installation and flexibility.
Rigid DPC
Made from rigid and durable materials such as cement concrete with waterproof additives, slate, or bricks soaked in bitumen. These are suitable for load-bearing walls and older construction methods.
Chemical DPC
This type is used in existing structures. It involves injecting waterproofing chemicals into brickwork or concrete to block moisture. Chemical DPC is ideal for retrofitting buildings already affected by damp.
Integral DPC
This involves mixing waterproofing compounds directly into the concrete during casting. It provides long-term moisture resistance and is commonly used in basements and foundations.
Common Materials Used in DPC
| Material | Description |
|---|---|
| Bituminous Felt | Flexible, easy to use, widely applied for horizontal DPC |
| Plastic Sheets | Lightweight, durable, commonly made from polythene |
| Mastic Asphalt | Strong, waterproof, long-lasting, suitable for both walls and floors |
| Cement Concrete | Rigid, often used with waterproofing agents |
| Bricks with Bitumen | Traditional method, rarely used now |
| Metal Sheets | Copper or lead sheets used in high-end or heritage buildings |
Methods of Damp Proof Course Application
Horizontal DPC
This is the most common type and is laid at plinth level, typically 150 mm above ground level, to prevent rising damp from the foundation.
Vertical DPC
Applied on vertical walls to prevent lateral moisture entry. Often used in combination with horizontal DPC for full protection.
Basement Tanking
Used in basements and below-ground structures. It involves coating or lining the entire surface with waterproof material to block water ingress.
Injection DPC
Used in older buildings, where chemicals are injected into the wall to fill pores and block moisture movement.
Where is DPC Applied?
- At the plinth level in external and internal walls
- Below ground level slabs or basement floors
- In retaining walls and foundation walls
- Around window and door frames
- At the junction of different building components
Best Practices for DPC Installation
- Ensure DPC is laid as a continuous layer without gaps or overlaps
- Avoid puncturing or damaging the DPC layer during further work
- Maintain a minimum height of 150 mm above ground level for horizontal DPC
- Select material appropriate for structural movement and moisture conditions
- Supervise and inspect regularly during installation
Benefits of Damp Proof Course (DPC)
- Prevents rising damp and keeps the structure dry
- Protects plaster, paint, woodwork, and finishes from moisture damage
- Prevents corrosion of steel and decay of timber
- Helps maintain good indoor air quality and prevent mold growth
- Increases the lifespan and performance of the building
- Reduces long-term maintenance and repair costs
- Improves thermal insulation by keeping walls dry
FAQs About Damp Proof Course (DPC)
What is the purpose of DPC?
To prevent moisture from the ground from rising into walls and floors, protecting the structure from damp-related damage.
What materials are used for DPC?
Bitumen, plastic sheets, mastic asphalt, metal sheets, cement concrete with waterproofing additives, and chemical solutions for injection.
Where is DPC placed in a building?
Generally at plinth level, about 150 mm above ground, and sometimes in floors, basements, and around openings.
Can DPC be added later to an old building?
Yes, chemical injection DPC is a popular retrofit solution for damp treatment in existing buildings.
Is DPC required in every construction project?
Yes, especially in areas with high ground moisture, DPC is a standard and necessary element in modern construction.
Conclusion
Knowing what is damp proof course (DPC) helps you protect your building from moisture damage right from the start. Whether it’s a residential home or a commercial complex, DPC is essential for ensuring that rising damp does not compromise strength, beauty, or health. By choosing the right type of DPC and installing it correctly, you can avoid structural issues, frequent maintenance, and expensive repairs. Moisture can silently damage a building over time, but a good DPC acts as a reliable guard against it. Make sure your building has a proper DPC to enjoy a long-lasting and durable structure.
