Water movement in buildings is one of the most important concerns in construction. Among the different types of water movement, Capillary action is one of the most common and often misunderstood problems. It can cause dampness, weaken materials, and reduce the life of structures. Therefore, understanding Capillary action is essential for engineers, site supervisors, and builders.
This blog explains Capillary action in simple British English, including its causes, effects, examples, standards, prevention methods, and a real case study.
What is Capillary Action?
Capillary action is the movement of water through small pores, cracks, or tiny spaces in materials without external force. This happens due to surface tension and adhesion between water and the material surface.
In construction, Capillary action occurs when water moves upward or sideways through concrete, bricks, plaster, and soil.
For example, when the bottom of a wall touches damp soil, water rises upward into the wall due to Capillary action. This is also called rising damp.
How Capillary Action Works
Capillary action happens due to two main forces:
- Adhesion – attraction between water and material surface
- Cohesion – attraction between water molecules
When these forces work together, water moves upward through small pores.
The smaller the pore size, the higher the Capillary action.
For example:
- Clay soil → High Capillary action
- Sand → Medium Capillary action
- Gravel → Low Capillary action
Where Capillary Action Occurs in Construction
Capillary action can occur in many construction elements, such as:
1. Concrete
Concrete contains tiny pores. Water moves through these pores due to Capillary action, causing dampness.
2. Brick Masonry
Bricks absorb water easily. Therefore, Capillary action is very common in brick walls.
3. Plaster
Plaster is porous. So, Capillary action can cause paint peeling and damp patches.
4. Foundations
When foundations touch wet soil, water moves upward through Capillary action.
5. Floors
Water rises from soil into floor slabs due to Capillary action if proper protection is not provided.
Effects of Capillary Action in Buildings
Capillary action can cause serious problems in buildings. Some major effects include:
1. Dampness in Walls
This is the most common effect. Damp patches appear on walls due to Capillary action.
2. Paint Peeling
Moisture from Capillary action causes paint failure and surface damage.
3. Structural Weakening
Water reduces concrete strength over time due to Capillary action.
4. Corrosion of Steel
Steel reinforcement corrodes when water reaches it through Capillary action.
5. Efflorescence
White salt deposits appear due to Capillary action.
6. Mould Growth
Moist conditions caused by Capillary action promote fungus and mould.
Real Case Study: Rising Damp in Residential Building
Project:
Residential building in Patna, India
Problem:
After one year of construction, damp patches appeared up to 1 metre above floor level.
Investigation:
Engineers found that no Damp Proof Course (DPC) was provided. Water from soil moved upward due to Capillary action.
Solution:
- Chemical DPC was installed
- Waterproof plaster was applied
- External drainage was improved
Result:
Dampness stopped within 3 months.
This case shows how Capillary action can damage buildings if ignored.
Example of Capillary Action in Construction
A simple example of Capillary action is placing a brick in water.
Observation:
Water rises upward inside the brick.
This shows how Capillary action works in real structures.
Another example is concrete placed directly on wet soil without protection. Water moves upward due to Capillary action.
Factors Affecting Capillary Action
Several factors influence Capillary action:
1. Pore Size
Smaller pores increase Capillary action.
2. Material Type
Porous materials like brick and concrete show higher Capillary action.
3. Moisture Availability
More water increases Capillary action.
4. Soil Type
Clay soil causes higher Capillary action than gravel.
5. Compaction
Dense concrete reduces Capillary action.
Standards Related to Capillary Action
Several standards address moisture and Capillary action control:
IS 3067: Code of Practice for General Design Details for Damp Proofing
This standard provides guidelines to prevent dampness caused by Capillary action.
IS 2645: Integral Cement Waterproofing Compounds
This standard recommends materials that reduce Capillary action.
IS 456: Plain and Reinforced Concrete Code
It recommends proper concrete mix and cover to reduce water penetration caused by Capillary action.
These standards help engineers control Capillary action effectively.
How to Prevent Capillary Action in Construction
Prevention of Capillary action is very important. Several methods are used.
1. Damp Proof Course (DPC)
DPC is the most effective method to stop Capillary action.
It is provided between foundation and wall.
Materials used:
- Bitumen
- Plastic sheets
- Waterproof mortar
2. Waterproofing
Waterproofing reduces Capillary action.
Methods include:
- Waterproof coatings
- Integral waterproofing compounds
- Membranes
3. Proper Concrete Mix
Dense concrete reduces pores and prevents Capillary action.
Use:
- Low water-cement ratio
- Proper compaction
- Proper curing
4. Providing Drainage
Good drainage reduces soil moisture and limits Capillary action.
5. Use of Damp Resistant Materials
Use materials with low water absorption to reduce Capillary action.
Modern Solutions to Control Capillary Action
Modern construction uses advanced methods to reduce Capillary action:
- Chemical waterproofing
- Crystalline waterproofing
- Waterproof admixtures
- Protective coatings
These methods improve durability and reduce damage.
Importance of Controlling Capillary Action
Controlling Capillary action provides many benefits:
- Improves building life
- Prevents dampness
- Protects reinforcement
- Improves structural strength
- Reduces maintenance cost
Therefore, controlling Capillary action is essential in construction.
Conclusion
Capillary action is a natural process, but it can cause serious problems in buildings if ignored. It leads to dampness, corrosion, and reduced structural life. However, proper design, waterproofing, DPC, and good construction practices can control Capillary action effectively.
Engineers and site supervisors must understand Capillary action and take preventive measures during construction. This ensures strong, durable, and long-lasting buildings.
FAQs on Capillary Action in Construction
1. What is Capillary action in construction?
Capillary action is the movement of water through small pores in construction materials.
2. Why is Capillary action harmful?
Capillary action causes dampness, corrosion, and structural damage.
3. Where is Capillary action most common?
Capillary action is common in foundations, brick walls, concrete, and plaster.
4. How can Capillary action be prevented?
It can be prevented using DPC, waterproofing, and proper construction methods.
5. Does concrete allow Capillary action?
Yes, concrete has pores, so Capillary action can occur.