Lesson Notes By Weeks and Term v5 - Grade 11

Lesson Video

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Performance objectives

• Explain types of superstructures (load-bearing vs. framed).
• Describe the process of building a brick wall.
• Identify common wall finishes like plastering, skimming, and painting.
• Explain how to install ceramic floor tiles.
• Understand the importance of quality control.

Lesson summary

This week, we delve into the exciting world of superstructures and finishes in construction. Superstructures are the "bones" of a building, the part that supports everything above the foundation. Finishes, on the other hand, are what make a building aesthetically pleasing and habitable – the plaster, paint, tiles, and flooring. Understanding these processes is crucial because it allows you to appreciate the complexities of building construction, opens doors to various career paths in the built environment (from construction management to skilled trades), and empowers you to make informed decisions about your own home or future construction projects.

Lesson notes

Superstructures: The Load-Bearing Framework A superstructure is the part of a building above the ground level. Its primary function is to support all the loads – the weight of the roof, walls, floors, occupants, and furniture – and transfer them safely to the foundation. We'll focus on two common types of superstructures: load-bearing walls and framed structures.

Load-Bearing Walls: Definition: These walls are designed to carry the weight of the structure above them. They are typically constructed from brick, concrete blocks, or reinforced concrete. In older South African homes and RDP housing, brick load-bearing walls are common.

Advantages: Relatively simple construction. Good thermal mass (helps regulate temperature). Can provide good sound insulation.

Disadvantages: Limited design flexibility – walls cannot be easily removed or altered. Can be more time-consuming to build than framed structures. Not ideal for large spans or open-plan designs.

Example: Imagine a simple, single-story brick house. The brick walls are supporting the roof. If you were to remove a load-bearing wall, the roof could collapse. Construction of a Brick Wall (Load-Bearing): Foundation: The foundation must be strong and level to support the wall.

Damp-Proof Course (DPC): A DPC (usually a layer of waterproof material like bitumen) is placed on top of the foundation to prevent rising damp. This is crucial to prevent dampness issues in the house.

Mortar Mixing: The mortar is a mixture of cement, sand, and water.

A common ratio for bricklaying is 1:6 (1 part cement to 6 parts sand).

The correct consistency is important: it should be plastic and workable, not too wet or too dry.

Importance of correct Mortar mix: too much cement can cause cracking; too little, and the wall will be weak.

Bricklaying: Bricks are laid in courses (horizontal layers), with mortar between each brick. The bricks should be staggered (overlapped) to create a strong bond. This is often done in a stretcher bond pattern, where the long side of the brick is visible.

Plumb and Level: It is essential to ensure the wall is plumb (vertical) and level throughout the construction process. Use a spirit level to check this regularly.

Wall Ties: Wall ties are metal strips that are embedded in the mortar joints to connect the brick wall to any internal walls or columns, providing additional stability.

Framed Structures: Definition: These structures use a framework of columns and beams (typically made of steel or reinforced concrete) to support the loads. The walls are non-load-bearing and simply fill in the spaces between the frame. These are common in modern high-rise buildings and warehouses.

Advantages: Greater design flexibility – walls can be moved or altered relatively easily. Suitable for large spans and open-plan designs. Can be faster to build than load-bearing walls.

Disadvantages: Generally more expensive than load-bearing wall construction. Requires skilled labor for design and construction. May require more insulation to achieve good thermal performance.

Example: Think of a steel-framed warehouse. The steel columns and beams are supporting the roof and walls. The walls themselves are often made of metal sheeting or concrete panels and are not load-bearing.

Finishes: Adding the Final Touches Finishes are the materials applied to the interior and exterior surfaces of a building to provide protection, improve aesthetics, and create a comfortable living environment. We'll look at common wall and floor finishes.

Wall Finishes: Plastering: Definition: Applying a layer of plaster (a mixture of cement, sand, and water, sometimes with lime) to a wall surface to create a smooth, even finish.

Purpose: Provides a smooth surface for painting or other finishes, improves insulation, and protects the wall from moisture.

Application: Plaster is applied in multiple layers, typically a scratch coat, a brown coat, and a finish coat. Each layer is allowed to dry before the next is applied.

Skimming: Definition: Applying a thin layer of joint compound (also known as drywall mud) to a wall to create a perfectly smooth surface for painting.

Purpose: Fills in imperfections and creates a seamless finish, especially on drywall surfaces.

Application: Skim coating is applied with a wide knife or trowel, ensuring a thin, even layer. It requires skill and patience to achieve a smooth result.

Painting: Definition: Applying a coat of paint to a wall for decoration and protection.

Purpose: Provides color, protects the wall from moisture and dirt, and can improve the overall appearance of the room.

Application: Walls are typically primed before painting. Two coats of paint are usually applied for best results.

Floor Finishes: Ceramic Tiles: Definition: Tiles made from clay that are fired at high temperatures.

Purpose: Durable, water-resistant, and easy to clean. Suitable for bathrooms, kitchens, and other high-traffic areas.