NCERT Class 9 Skill Education Important Chapter 6 Construction

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NCERT Class 9 Skill Education Important Chapter 6 Construction

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Construction

Chapter: 6

IMPORTANT SOLUTIONS

A. Short Question Answer:

1. What are the primary uses of dams in India? 

Ans: Dams are used to provide irrigation for agriculture, generate electricity, control floods, and provide drinking water.

2. Which dam is highlighted as one of the highest in India, and what is its height? 

Ans: The Tehri dam in Uttarakhand is one of the highest in India, standing at a height of 261 meters..

3. What are the two main types of building construction based on how weight is supported? 

Ans: The two main types are load-bearing (wall-bearing) construction and RCC (Reinforced Cement Concrete) construction.

4. Why is load-bearing construction commonly chosen for single-storey houses? 

Ans: It is simple in design, costs less to build, and is very easy to repair.

5. How is the load carried in RCC construction? 

Ans: In RCC construction, the building stands on a strong skeleton frame of concrete and steel columns and beams that carry the load to the ground, rather than relying on the walls.

6. What is the purpose of a foundation in a building? 

Ans: A strong foundation increases a building’s lifespan, prevents cracks in the structure, and protects against natural calamities like earthquakes.

7. What is the difference between beams and columns? 

Ans: Beams are horizontal elements that carry the weight of the upper floors or roof, while columns are vertical elements that support the beams and transfer the building’s weight to the foundation.

8. What ingredients are mixed together to make mortar? 

Ans: Mortar is a mixture of sand, cement, and water.

9. What is the main difference between mortar and concrete?

Ans: Mortar is used to bind materials together (like gluing bricks), whereas concrete includes gravel or crushed stones and is used to create the actual structure and support heavy weight.

10. What is the standard size of a brick in India? 

Ans: The standard size of a brick in India is 190 × 90 × 90 mm.

11. Why must bricks be soaked in water before they are used in construction? 

Ans: Bricks must be soaked for 6–12 hours so that they do not absorb the water out of the mortar.

12. What does “curing” mean in construction?

Ans: Curing is the vital process of keeping new construction wet for 14–28 days to complete the chemical reaction that strongly bonds the materials together.

13. What tool is specifically used to ensure a wall is perfectly vertical? 

Ans: A plumb bob is used to check vertical alignment so that gravity does not weaken the structure.

14. What tool is used to ensure a surface is perfectly horizontal? 

Ans: A spirit level is used to check if a surface is perfectly parallel to the ground.

15. What is the function of a water level tube? 

Ans: It is a long, transparent rubber tube filled with water used to check if two distant points of a construction project are at the exact same height.

16. What is an English bond in bricklaying? 

Ans: Considered one of the strongest bonds, it is a pattern of alternate rows of stretcher bonds (length facing front) and header bonds (width facing front).

17. What is a Bill of Materials (BoM)? 

Ans: A BoM is a list used to estimate construction costs in advance, helping to avoid waste by ensuring only the necessary items are purchased.

18. What is the general cement-to-sand ratio for interior and exterior plastering? 

Ans: The typical ratio is 1:6 for external plastering and 1:4 for interior plastering.

19. What hand tool is used for lifting, spreading, and smoothening mortar? 

Ans: A trowel, also known as a Karni or Thappa, is used for this task.

20. What are the unique benefits of using whitewash (lime wash) for painting? 

Ans: Whitewash is very inexpensive, has antibacterial properties, reflects heat well, and is eco-friendly.

B. Long Question Answer.

1. What are the two main types of building construction based on how weight is supported, and how do they differ in design and application? 

Ans: Housing construction is primarily divided into two main types based on weight support: load-bearing (wall-bearing) construction and RCC (Reinforced Cement Concrete) construction. In load-bearing construction, the walls themselves carry the entire weight of the roof and upper parts of the building, transferring it directly to the ground. This method is commonly used for single-storey houses and areas where deep foundations are not needed, as these structures are simple in design, cost less to build, and are extremely easy to repair. Conversely, in RCC construction, the building stands on a strong skeleton frame of columns and beams made of concrete and steel. In this type, the heavy load of the slab and floors is transferred to the ground through the frame rather than the walls. RCC construction is essential for multi-storey buildings and structures that must be exceptionally strong and earthquake-resistant.

2. What are the sequential steps involved in making a basic brick structure, from preparation to plastering? 

Ans: The construction of a basic brick structure involves several detailed phases. First, the ground must be prepared by cleaning the site, removing loose soil, and sprinkling water to settle any dust. Next, the layout is marked on the ground using a meter tape and a pointed stick. A foundation is then prepared, which involves levelling the surface, removing extra soil, and using a spirit level and water level tube to ensure absolute flatness. A reference line is established using string or chalk to ensure correct alignment before laying begins. During bricklaying, bricks must be soaked in water for 6–12 hours to prevent them from absorbing water directly out of the mortar. Bricks are laid in a specific bond pattern, and mortar is applied between them. To maintain structural integrity, tools like a plumb bob, spirit level, and water level tube are used to ensure proper alignment. Finally, the structure undergoes curing and plastering, where a smooth or textured coating of plaster is applied to increase durability and protect the wall from moisture.