Lesson Notes By Weeks and Term v5 - Grade 10
Roofs, doors and windows: basic construction details – Week 10 focus
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Roofs, doors and windows: basic construction details – Week 10 focus
Download the Lessonotes Mobile South Africa app for faster lesson access on Android and iPhone.
Subject: Civil Technology
Class: Grade 10
Term: 3rd Term
Week: 10
Theme: General lesson support
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In South Africa, understanding the basics of roofs, doors, and windows is crucial for building safe, durable, and comfortable homes and buildings. This knowledge is relevant whether you plan to become a construction worker, architect, engineer, or simply a homeowner. Understanding how these components are constructed allows you to appreciate the quality of buildings around you, identify potential problems, and even contribute to sustainable and cost-effective building practices. This week, we'll focus on the fundamental construction details of these essential elements. We will cover common roof types, door and window frames, materials used, and the principles of installation.
2.1 Roofs: Basic Construction Details Roofs protect buildings from the elements, providing shelter and contributing to structural stability.
Common roof types in South Africa include: Gable Roof: This is a simple, pitched roof with two sloping sides that meet at a ridge. It's easy to construct and provides good ventilation.
However, it can be vulnerable to wind damage in areas with strong winds.
Components: Rafters (sloping members supporting the roof covering), purlins (horizontal members supporting the rafters), ridge board (at the apex of the roof), roof covering (tiles, corrugated iron, etc.), fascia board (covering the rafter ends), and soffit (underneath the overhang).
Construction Details: Rafters are typically spaced evenly and connected to the wall plate (horizontal timber fixed to the top of the wall) and the ridge board. Purlins provide intermediate support to the rafters. The roof covering is then attached to the rafters or battens (smaller timber members fixed to the rafters).
Hip Roof: A hip roof has sloping sides and sloping ends that meet at hips (external corners). It's more resistant to wind damage than a gable roof.
Components: Similar to a gable roof but includes hip rafters (sloping members running from the corner of the building to the ridge) and jack rafters (shorter rafters that meet the hip rafters).
Construction Details: Hip rafters are placed at the corners of the building, and jack rafters connect them to the wall plate and ridge. This creates a more complex and stable structure.
Lean-to Roof: A single sloping roof attached to an existing wall or structure. It's often used for extensions or sheds.
Components: Rafters, wall plate, roof covering.
Construction Details: Rafters are attached to the wall plate and slope upwards to the supporting structure.
Roof Covering Materials in South Africa: Common materials include corrugated iron (affordable and durable), concrete tiles (fire-resistant and long-lasting), clay tiles (traditional and aesthetically pleasing), and thatch (natural and provides good insulation). The choice depends on budget, climate, and aesthetic preferences. In coastal regions, corrosion-resistant materials are essential.
Example: Consider a small house in Durban. A corrugated iron gable roof is chosen due to its affordability and ability to withstand heavy rainfall. The roof pitch (angle of the roof) should be steeper to allow for quick water runoff. 2.2 Doors: Basic Construction Details Doors provide access and security. Understanding door frame construction is critical for proper installation.
Wooden Door Frames: Typically made of softwood or hardwood.
Components: Jambs (vertical members), head (horizontal member), sill/threshold (bottom member), and stops (against which the door closes).
Construction Details: The jambs and head are joined together to form a rectangular frame. The frame is then fixed to the wall using screws or nails, ensuring it's plumb (perfectly vertical) and level (perfectly horizontal). The sill/threshold provides a transition between the inside and outside. The stops are fixed to the frame to prevent the door from swinging too far.
Metal Door Frames: Often made of steel or aluminum.
Components: Similar to wooden frames but made of metal.
Construction Details: Metal frames are often welded together for strength. They are fixed to the wall using anchors or bolts. Metal frames are more durable and resistant to fire than wooden frames.
Thresholds: Thresholds are important for weather sealing and preventing drafts. Different threshold designs are available, including raised thresholds, ramps (for accessibility), and adjustable thresholds.
Example: A low-cost housing project uses wooden door frames. To prevent rot and insect damage, the frames are treated with a preservative before installation. A raised threshold is used to prevent water from entering the house during heavy rains. 2.3 Windows: Basic Construction Details Windows provide light, ventilation, and views. The type of window frame affects its performance and appearance.
Wooden Window Frames: Traditional and aesthetically pleasing.
Components: Similar to door frames (jambs, head, sill), sash (the part that holds the glass), and glazing beads (to hold the glass in place).
Construction Details: The frame is constructed similarly to a door frame. The sash is fitted into the frame and can be fixed or operable (able to be opened). Glazing beads secure the glass within the sash.
Aluminum Window Frames: Lightweight, durable, and resistant to corrosion.
Components: Extruded aluminum profiles joined together to form the frame and sash.
Construction Details: Aluminum frames are often powder-coated for durability and aesthetics. They are fixed to the wall using screws or anchors. uPVC Window Frames: Low maintenance, energy-efficient, and resistant to weather.
Components: uPVC (unplasticized polyvinyl chloride) profiles joined together to form the frame and sash.