Lesson Notes By Weeks and Term v5 - Grade 10

Lesson Video

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Performance objectives

• Identify common South African brick types.
• Sketch and explain Stretcher and English bonds.
• Describe how to prepare mortar.
• Explain the purpose of a Damp Proof Course (DPC).
• Calculate the number of bricks for a simple wall.

Lesson summary

Masonry and brickwork are fundamental to the construction industry in South Africa. From building homes and schools to creating infrastructure like walls and paving, understanding the basics of masonry is crucial for any aspiring civil technologist. This week, we will delve into the essentials of brickwork, focusing on brick types, bonding patterns, and the preparation of mortar. These skills are not just theoretical; they are directly applicable to building a better future for our communities by constructing safe, durable, and aesthetically pleasing structures.

Lesson notes

2.1 Brick Types in South Africa: South African National Standards (SANS) define the specifications for bricks, ensuring quality and consistency.

Here are some common types: Clay Bricks: These are the most widely used type. They are manufactured by firing clay in a kiln. Clay bricks are known for their durability, strength, and fire resistance.

Common Clay Bricks:* Used for general building purposes where aesthetics are not critical (e.g., inner walls).

Face Bricks:* These have a smoother, more attractive finish and are used for exposed walls. They come in various colours and textures. Remember to consider the SANS standards relevant to specific face brick requirements.

Engineering Bricks:* High-strength bricks used in load-bearing applications where structural integrity is paramount (e.g., foundations, retaining walls).

Concrete Bricks/Blocks: Made from a mixture of cement, sand, and aggregates. Concrete blocks are larger than clay bricks, which speeds up construction.

Hollow Concrete Blocks:* Lighter than solid blocks and provide better insulation. They are often used for walls where insulation is important.

Solid Concrete Blocks:* Stronger than hollow blocks and used in load-bearing walls.

Stock Bricks: Often re-claimed or less visually perfect bricks. Can be suitable for infill or secondary construction. 2.2 Brick Bonding: Bonding refers to the arrangement of bricks in a wall to provide strength, stability, and aesthetic appeal. The bond pattern distributes loads evenly and prevents continuous vertical joints, which would weaken the wall.

Stretcher Bond: The simplest bond, consisting of bricks laid lengthwise (stretchers) on each course. This bond is commonly used for single-skin walls or cladding because it's fast and economical.

However, it's not very strong for load-bearing walls thicker than one brick.

English Bond: One of the strongest bonds. It consists of alternating courses of headers (bricks laid with their short face showing) and stretchers. A queen closer (a brick cut lengthwise to half its width) is used in the header course next to the quoin (corner) to maintain the bond and prevent vertical joints aligning. This bond is excellent for load-bearing walls.

Header Bond: Consists of all headers in each course. Usually used for single skin walls with curves or for specialised detailing.

Flemish Bond: Each course consists of alternating headers and stretchers. The headers are centered above the stretchers in the course below. A closer is placed next to the quoin header in alternate courses. This bond is aesthetically pleasing and provides good strength. 2.3 Mortar Preparation: Mortar is the paste that binds bricks together. A good mortar mix is crucial for the strength and durability of the brickwork.

The typical mortar mix ratio is 1:6 (cement:sand) by volume for general brickwork. For engineering brickwork, a stronger mix of 1:4 (cement:sand) may be required. Never use pure cement as a mortar – it will crack and be too hard.

Materials: Cement:* Ordinary Portland cement (OPC) is commonly used.

Sand:* Use clean, well-graded river sand that is free from organic matter and clay.

Water:* Clean, potable water.

Procedure: Measure the required amounts of cement and sand accurately. Thoroughly mix the dry ingredients until a uniform colour is achieved. This ensures even distribution of the cement. Gradually add water, mixing continuously, until the mortar reaches a plastic, workable consistency. It should be able to hold its shape and adhere to the trowel without being too runny. Allow the mortar to stand for about 10 minutes (slaking) to improve workability. Remix before use.

Why the right mix matters: Too much cement makes the mortar hard and brittle, leading to cracking. Too little cement results in a weak bond that can easily crumble. The correct water content ensures workability and proper hydration of the cement. 2.4 Damp Proof Course (DPC): A DPC is a horizontal barrier placed in a wall to prevent rising damp. Rising damp occurs when groundwater is drawn up through the brickwork by capillary action.

DPCs are typically made of: Bitumen felt:* A flexible, waterproof material.

Plastic membrane:* Durable and resistant to degradation. The DPC is usually placed at least 150mm above ground level to prevent water from splashing onto the wall. It is crucial to install the DPC correctly, ensuring a continuous barrier across the entire wall width. 2.5 Calculating Brick Quantities: To estimate the number of bricks needed for a wall, you need to consider the wall dimensions, brick size, mortar joint thickness, and bond type. A standard brick size is approximately 222mm (length) x 106mm (width) x 73mm (height). A typical mortar joint thickness is 10mm. Wastage must also be factored in (usually 5-10%).

Example: Calculate the number of bricks required for a wall 5m long, 2m high, and one brick thick (230mm) using a stretcher bond. Consider 10mm mortar joints and 5% wastage.