Chajjahs – Characteristics, Centring & Shuttering
Chajjahs, also known as sunshades, are horizontal or slightly inclined projections provided above doors, windows, and ventilators. They are an important part of building construction as they protect openings from rainwater and direct sunlight. In the ITI Draughtsman Civil trade, understanding chajjahs is essential for preparing building drawings and ensuring proper protection of structures.
Chajjahs not only serve a functional purpose but also enhance the appearance of buildings.
Characteristics of Chajjahs
A good chajjah should have the following characteristics:
- Projection: It should extend sufficiently beyond the opening to protect from rain and sun.
- Slope: It should have a slight slope to allow rainwater to drain off.
- Strength: It should be strong enough to support its own weight and external loads.
- Durability: It should resist weathering and environmental effects.
- Waterproofing: It should prevent water seepage.
These characteristics ensure effective performance and long life of chajjahs.
Types of Chajjahs
Chajjahs are constructed using different materials:
- RCC Chajjah: Most common type, strong and durable.
- Stone Chajjah: Used in traditional construction.
- Brick Chajjah: Used for small projections.
Centring of Chajjahs
Centring is a temporary support provided during the construction of chajjahs until the material gains sufficient strength. It ensures proper shape and alignment.
Purpose of Centring:
- Supports the chajjah during casting
- Maintains correct slope and level
- Prevents deformation or collapse
Materials Used for Centring:
- Timber
- Steel frames
Requirements of Good Centring:
- Strong and stable
- Easy to assemble and remove
- Accurate in shape and size
Shuttering of Chajjahs
Shuttering is the process of providing a temporary mould or formwork into which concrete is poured to shape the chajjah.
Functions of Shuttering:
- Provides shape and support to concrete
- Maintains dimensions and finish
- Holds concrete until it sets
Types of Shuttering Materials:
- Timber shuttering
- Steel shuttering
- Plywood shuttering
Requirements of Good Shuttering:
- Leak-proof to prevent loss of cement paste
- Strong enough to carry loads
- Smooth surface for good finish
Shuttering is removed after the concrete has gained sufficient strength.
Advantages of Chajjahs
- Protects openings from rain and sunlight
- Reduces heat inside the building
- Improves appearance of structure
Limitations
- Requires proper design and support
- May develop cracks if not constructed properly
Applications in Construction
Chajjahs are widely used in:
- Residential buildings
- Commercial structures
- Public buildings
Importance in Draughtsman Civil Trade
Knowledge of chajjahs, centring, and shuttering helps draughtsmen in preparing detailed drawings and ensuring proper construction. It also helps in selecting suitable materials and methods.
Conclusion
Chajjahs are important building elements that provide protection and enhance the appearance of structures. Proper centring and shuttering are essential for their construction.
For students of the ITI Draughtsman Civil trade, understanding these concepts is crucial for designing safe and efficient buildings. Proper construction ensures durability and effective performance of chajjahs.