Bricks have been the backbone of construction for centuries. From mighty castles to cosy homes, bricks have shaped the world we live in. But not all bricks are created equal. They’re classified into various types based on their quality, strength, and purpose. Today, we’ll dive into third class bricks — the unsung heroes (or the risky picks) of construction.
Are they all bad? Not really. But there’s a reason why they’re called “third class.” Let’s understand why these bricks exist, where they’re used, and what makes them different from their premium counterparts.
What Are Third Class Bricks?
Third class bricks are low grade bricks made from poor-quality clay and fired at low temperatures. These bricks don’t pass the standard tests for strength and durability. They are soft, porous, and often break easily under pressure.
They are commonly used in temporary or non-load-bearing structures—such as boundary walls or garden pavements—not in places where safety or longevity are top priorities.
Appearance and Structure
If you’ve ever seen a brick that:
- Crumbles when dropped,
- Has rough surfaces,
- Looks uneven and deformed,
- Then you’re probably looking at a third-class brick.
These bricks often have a dull or dark colour due to uneven burning and high moisture absorption.
Properties of Third Class Bricks
Physical Properties
- Shape & Texture: Irregular shape, rough surface
- Colour: Dull red or brown
- Water Absorption: >25% (quite high)
- Efflorescence: Common
Mechanical Properties
- Compressive Strength: Below 3.5 N/mm²
- Durability: Very poor
- Load Bearing: Not suitable
Thermal and Weather Resistance
- Weak against rain and frost
- Not ideal for outdoor, long-term use
Manufacturing of Third Class Bricks
Raw Materials Used
Low-grade clay with high organic impurities is typically used. These bricks are often made locally with minimal quality control.
Firing Process
They are either underburnt or unevenly burnt, often in clamp kilns, which leads to soft and crumbly structures.
Where Are Third Class Bricks Used?
You’ll most likely find third class bricks in:
- Temporary structures (sheds, site offices)
- Boundary walls
- Garden edging and footpaths
- Rural construction where cost matters more than durability
Situations to Avoid Their Use
- Structural walls
- Multi-storey buildings
- Wet areas (like bathrooms or basements)
- Foundations
Advantages of Third Class Bricks
Cost-Effective
Third class bricks are very inexpensive—perfect for projects on a tight budget.
Readily Available
They’re locally produced, making them accessible in most rural or semi-urban areas.
Good for Temporary Work
Need a structure that’ll stand for just a few months or years? These bricks are a great fit.
Disadvantages of Third Class Bricks
Low Strength
Don’t even think about using them in your main building frame. Their compressive strength is extremely low.
Not Durable
These bricks disintegrate in rain and crack under pressure.
Poor Aesthetics
They’re not suitable for visible areas or plastering—unless you enjoy cracks.
Comparison: First, Second & Third Class Bricks
| Feature | First Class | Second Class | Third Class |
|---|---|---|---|
| Quality | Excellent | Good | Poor |
| Appearance | Uniform, sharp | Slightly irregular | Rough, deformed |
| Water Absorption | <15% | <20% | >25% |
| Strength | High | Medium | Low |
| Best Use | Load-bearing walls | Internal partitions | Temporary structures |
Tips for Identifying Third Class Bricks
Water Absorption Test
Soak in water for 24 hours. If weight increases by more than 25%, it’s third class.
Sound Test
Strike two bricks together. If the sound is dull, it’s likely third class.
Drop Test
Drop from a height of 1 meter. If it breaks easily, it’s third class.
Alternatives to Third Class Bricks
- Stabilised Mud Blocks: More eco-friendly and slightly more durable
- Concrete Bricks: Better uniformity and strength
- AAC Blocks: Lightweight, fire-resistant, better insulation
Third class bricks may not be ideal for your dream home, but they still serve a purpose. When cost is the top concern and longevity isn’t, they can be the right choice. But always use them wisely, and never in structural or moisture-prone areas.
FAQs
Are third class bricks safe for building houses?
No. They lack the strength and durability required for permanent residential structures.
How much water can third class bricks absorb?
They typically absorb more than 25% of their weight, making them unsuitable for wet areas.
Can I use third class bricks for compound walls?
Yes, they are commonly used for non-structural boundary walls, especially in rural areas.
Are third class bricks eco-friendly?
Not particularly. Their poor durability leads to faster disposal and replacement, increasing material waste.
How can I identify third class bricks at a site?
Look for irregular shape, dull sound when struck, soft texture, and high water absorption during tests.