Lesson Notes By Weeks and Term v5 - Grade 10
Roofs, doors and windows: basic construction details – Week 6 focus
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Roofs, doors and windows: basic construction details – Week 6 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: 6
Theme: General lesson support
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Roofs, doors, and windows are fundamental components of any building, providing shelter, security, access, light, and ventilation. Understanding their construction details is crucial for civil technologists. In South Africa, where housing needs are diverse and often constrained by resources, a solid grasp of these elements is essential for designing and constructing safe, functional, and sustainable buildings. This week's focus is on developing a foundational understanding of the basic construction details of roofs, doors, and windows.
2.1 Roofs: Pitched Roof Construction Pitched roofs are commonly used in South Africa due to their effectiveness in shedding water and their relatively simple construction.
Let's break down the key components: Rafters: These are sloping structural members that extend from the ridge (the highest point of the roof) to the wall plate (a horizontal timber member sitting on top of the wall). Rafters are spaced at regular intervals (typically 400mm to 600mm apart, depending on the load and timber size) and provide the primary support for the roofing material. The size of the rafters depends on the span (distance between supports), the roof pitch, and the weight of the roofing material.
Purlins: These are horizontal beams that run perpendicular to the rafters, providing intermediate support. They are typically supported by trusses or load-bearing walls. Purlins help to reduce the span of the rafters, allowing for smaller rafter sizes. In simpler roof structures, purlins may not be necessary.
Battens: These are thin strips of timber or steel that are fixed horizontally to the rafters (or purlins, if present). They provide a fixing point for the roofing material, such as tiles, corrugated iron, or slates. The spacing of the battens depends on the type of roofing material being used.
Ridge Board: This is a horizontal timber member that runs along the ridge of the roof, providing a fixing point for the rafters. It also helps to maintain the alignment of the roof.
Wall Plate: A horizontal timber member fixed to the top of the wall. Rafters rest on this, distributing the load along the wall.
Roofing Materials: These can include corrugated iron, roof tiles (concrete, clay), thatch, slate, or shingles. The choice of material depends on cost, availability, aesthetics, and the local climate. Consider how corrugated iron is common in low-cost housing due to its affordability and ease of installation.
However, it can be noisy during rain and provides less insulation than tiled roofs.
Overhang: The portion of the roof that extends beyond the walls of the building. Overhangs protect the walls from rain and sun.
Verge: The edge of the roof that runs parallel to the gable end of the building.