Building Construction MCQ Questions & Answers | Civil Engineering

Hacking: This is the process of roughening a surface before plastering. Think of it like creating a texture so the plaster has something to really grip onto. This ensures the plaster sticks well and doesn't fall off later.

Dubbing: Dubbing out refers to filling up uneven surfaces (like holes or gaps) to create a more even base before the final plaster layer.
It's more about leveling than roughening the existing surface.

Blistering: This is a *defect* in plastering, not a preparation method. It's when bubbles form under the surface.

Peeling: Similar to blistering, peeling is also a *defect* where the plaster layer starts to separate and come away from the wall.

So, to make the background rough before plastering, we use hacking to create a good bonding surface.

Let's understand what Construction Joints are and why they are important in buildings.

Imagine you are building a very long concrete wall or a big concrete floor.
It's practically impossible to pour all the concrete at once in one go. So, engineers plan specific places to stop pouring concrete for the day and then continue the next day. These planned stopping points are called Construction Joints.

But these joints are not just about stopping work. They also serve a very important purpose related to the concrete itself:
Concrete Shrinkage and Expansion:
When concrete dries, it shrinks a little bit. Also, concrete can expand when it's hot and contract when it's cold. If you have a very long piece of concrete without any breaks, these changes in size can create a lot of stress and might cause the concrete to crack randomly.

To prevent these unwanted random cracks, we put in Construction Joints (which often double as or are placed near Movement Joints or Expansion Joints). These joints act like planned "breaks" in the concrete, allowing it to expand, contract, and shrink in a controlled way without causing damage.

Now, about the spacing:
How far apart should these joints be? This depends on many factors like the type of building, type of concrete, and climate. However, for general building construction, a common and recommended practice is to provide these joints at intervals of about 20 meters.

So, if you have a very long wall or floor, you would put a construction joint roughly every 20 meters. This helps to keep the concrete structure stable and prevents uncontrolled cracking over time.

Therefore, the correct answer is Option C: 20 m.