Lesson Notes By Weeks and Term v3 - Senior Secondary 2
Details of Parts of Building
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Details of Parts of Building
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Subject: Technical Drawings
Class: Senior Secondary 2
Term: 1st Term
Week: 10
Theme: Building And Engineering Design And Drawing
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Identify parts of a building. Draw details of parts of a building.
This section provides a detailed explanation of common building parts, focusing on their function, typical materials used in Nigeria, and crucial aspects for technical representation.
A. Foundation: The lowest part of a structure that transfers the load of the building to the ground.
Function: To safely transmit the entire load of the structure to the underlying soil, preventing settlement and ensuring stability.
Common Types in Nigeria: Strip Foundation: Most common for load-bearing walls in residential buildings on stable soil. It consists of a continuous strip of concrete, wider than the wall it supports, distributing the load over a larger area.
Detail for Drawing: Show the concrete strip (often 225-300mm deep, extending 150mm beyond each face of the wall), the block wall starting from the foundation, and the excavated earth line. Reinforcement details might be simplified for SS
2. Raft Foundation (Mat Foundation): A large slab covering the entire area of the building, used on soft or expansive soils where individual strip or pad foundations would cause differential settlement.
Detail for Drawing: Represent as a reinforced concrete slab beneath the entire building footprint, often with thickening under load-bearing walls.
Pad Foundation: Used for isolated columns, typically in framed structures. Each column has its own concrete pad.
Detail for Drawing: Show a rectangular or square concrete pad supporting a column.
Materials: Primarily mass concrete (cement, sand, aggregates), sometimes reinforced concrete for deeper or heavy-load foundations. Hardcore (broken stones, laterite) is often used beneath ground floor slabs within the foundation perimeter.
B. Walls: Vertical elements enclosing or dividing spaces.
Function: To enclose spaces, provide structural support (load-bearing walls), divide rooms (partition walls), provide privacy, and offer protection from weather.
Common Types in Nigeria: Load-bearing Walls: Support the weight of the roof and upper floors. Typically 225mm (9 inches) thick sandcrete block walls or burnt bricks.
Non-load-bearing Walls/Partition Walls: Only support their own weight and perhaps minor fixtures. Typically 150mm (6 inches) thick sandcrete block walls.
Materials: Sandcrete Blocks: Most prevalent in Nigeria (9-inch for external/load-bearing, 6-inch for internal/partition).
Burnt Bricks: Used for aesthetic or specific structural requirements.
Laterite Blocks/Stabilized Earth Blocks: Increasingly used for sustainable and cost-effective construction in some regions.
Key Details for Drawing: Damp Proof Course (DPC): A layer of impervious material (e.g., bitumen felt, polythene sheet, cement-sand mortar with waterproofing admixture) laid horizontally in walls, usually 150mm above the finished ground level, to prevent rising dampness.
Drawing: Represent as a thick, dark line or a specific symbol within the wall section.
Wall Ties: Metal ties (e.g., butterfly ties) embedded in mortar joints to connect two wythes of a cavity wall or to tie non-load-bearing walls to columns/main walls.
C. Floors: Horizontal surfaces that support occupants and their belongings.
Function: To provide a level surface for occupation, transfer loads to walls/columns, and separate stories.
Common Types in Nigeria: Ground Floor: Slab on Hardcore: A common construction. Consists of a layer of compacted hardcore (150-200mm) for drainage and load distribution, followed by a Damp Proof Membrane (DPM - usually thick polythene sheet) to prevent moisture ingress, and finally a reinforced concrete slab (100-150mm thick).
Detail for Drawing: Show compacted hardcore, DPM, concrete slab, and often a screed (cement-sand mortar for leveling) with a final finish (tiles, terrazzo).
Upper Floors: Reinforced Concrete Slab: Most common for multi-story buildings. A monolithic slab cast in-situ, supported by beams and columns.
Detail for Drawing: Show the thickness of the slab, reinforcement (simplified for SS2), and floor finishes.
D. Roofs: The uppermost covering of a building.
Function: To protect the building and its occupants from weather elements (rain, sun, wind) and provide insulation.
Common Types in Nigeria: Gable Roof: Two sloping sides that meet at a ridge, forming a triangular shape at the ends.
Hip Roof: All sides slope downwards to the walls, usually with a consistent slope.
Lean-to Roof: A single-slope roof, often used for extensions or smaller structures. Components for Drawing (Gable Roof Example): Wall Plate: Timber member fixed to the top Roofs: The uppermost covering of a building.
Function: To protect the building and its occupants from weather elements (rain, sun, wind) and provide insulation.
Common Types in Nigeria: Gable Roof: Two sloping sides that meet at a ridge, forming a triangular shape at the ends.
Hip Roof: All sides slope downwards to the walls, usually with a consistent slope.
Lean-to Roof: A single-slope roof, often used for extensions or smaller structures. Components for Drawing (Gable Roof Example): Wall Plate: Timber member fixed to the top of the wall, supporting the rafters.
Rafters: Sloping timber members that support the roof covering.
Purlins: Horizontal timber or metal members spanning between trusses or gable walls, supporting the rafters.
Trusses: Structural frameworks (usually timber or steel) that support the roof covering and transmit loads to the walls/columns.
Ridge: The highest horizontal line where two opposing roof surfaces meet.
Eaves: The part of the roof that overhangs the wall, protecting it from rain.
Detail for Drawing: Show fascia board (conceals rafter ends), soffit (underside of eaves overhang), and gutter (collects rainwater).
Covering Materials in Nigeria: Long-span Aluminium Sheets: Very popular, durable, and lightweight.
Corrugated Iron Sheets: Traditional, cost-effective.
Asbestos-cement Sheets: Less common now due to health concerns, but still found.
Concrete Tiles: For specific aesthetic or structural requirements.
E. Doors: Openings for access.
Function: To provide access, security, and privacy.
Common Types in Nigeria: Flush Doors: Smooth, plain surfaces, common internally.
Panel Doors: Frames with recessed panels, often used externally.
Ledged and Braced Doors: Simple timber doors, often for utility rooms or less formal access.
Components for Drawing: Door Frame: The surrounding structure fixed to the wall opening.
Door Leaf (Sash): The moving part of the door.
Architrave: Decorative moulding around the door frame.
Hinges: Allow the door to swing.
Lock/Handle: For security and operation.
Typical Sizes in Nigeria: Main entry: 900mm x 2100mm; Internal: 750mm-900mm x 2100mm.
F. Windows: Openings for light and ventilation.
Function: To admit natural light, provide ventilation, offer views, and contribute to aesthetics.
Common Types in Nigeria: Casement Windows: Hinged at the side, swinging outwards.
Sliding Windows: Sash slides horizontally.
Louvre Windows (Jalousie Windows): Consist of parallel glass (or metal) slats that open and close like blinds. Very common in Nigeria for ventilation.
Components for Drawing: Window Frame: The surrounding structure fixed to the wall opening.
Sash: The moving part of the window, holding the glazing.
Glazing: Glass panes.
Sill (Cill): The bottom part of the window frame, sloped outwards to shed water.
Lintel: A horizontal beam (reinforced concrete or timber) placed over an opening (door or window) to support the wall above it.
Typical Sizes in Nigeria: Vary greatly, but common residential heights range from 1200mm to 1500mm, with widths from 600mm to 1800mm or more.
G. Stairs: A series of steps for ascending or descending between levels.
Function: To provide safe and easy vertical circulation within a building.
Components for Drawing: Tread: The horizontal surface of a step.
Riser: The vertical part between two treads.
Stringer (String): The sloping member supporting the ends of the treads and risers.
Newel Post: The main post at the top or bottom of a flight of stairs, or at a landing.
Balusters: Vertical posts supporting the handrail.
Handrail: The rail for support.
Basic Geometry: Tread depth (300mm standard), Riser height (150-175mm standard).
Rule: 2R + T = 600-650mm (comfort formula).
H. Lintels and Beams: Lintel: (As described above for windows) A horizontal structural member spanning an opening (door, window) to support the wall above it. Usually reinforced concrete in Nigeria.
Beam: A larger horizontal structural member supporting loads from slabs, walls, or other beams, and transferring them to columns or walls. Typically reinforced concrete.
I. Columns: Function: Vertical structural members that transmit axial compressive loads from beams or slabs to the foundation. * Materials:** Typically reinforced concrete in framed structures.
Phase 1: Introduction and Identification (30 mins)
Teacher Activity: Begins by displaying a large, clear diagram/poster of a simple residential building cross-section and plan. Introduces the concept of building components and their importance. Systematically points to and names each major part (foundation, walls, DPC, floor, roof, eaves, door, window, lintel, sill, etc.) on the diagram. Briefly explains the primary function of each identified part and common materials used in Nigeria. Asks probing questions to gauge prior knowledge and encourage student engagement (e.g., "Why do we need a DPC in our walls, especially with our rainy season?").
Student Activity: Actively observes the diagrams and listens to the explanations. Takes notes on the names and functions of building parts. Participates in discussions, attempting to identify parts and answer questions. Students may be asked to identify similar parts on photos of local Nigerian buildings (if available).
Phase 2: Detailed Explanation and Drawing Conventions (60 mins)
Teacher Activity: Selects specific key details (e.g., foundation detail, DPC detail, window sill/lintel detail, eaves detail). Explains the technical drawing conventions for representing these details (line types, symbols for materials, dimensioning rules). Demonstrates step-by-step on the whiteboard or projector how to draw a selected detail (e.g., a strip foundation with DPC and ground floor slab), explaining each line and dimension. Emphasises common Nigerian dimensions (e.g., 225mm wall, 100mm slab, 150mm DPC height above ground). Explains how to label and dimension the drawn detail accurately. Encourages students to ask questions for clarification.
Student Activity: Observes the teacher's demonstration carefully, paying attention to drawing techniques and conventions. Takes detailed notes on the specific components, materials, dimensions, and drawing steps. Practices sketching the demonstrated details in their drawing books or on loose sheets, focusing on accuracy and neatness. Asks questions for clarification on specific details or drawing techniques.
Phase 3: Practical Application and Guided Drawing (30 mins)
Teacher Activity: Provides students with a drawing task focusing on another specific detail (e.g., a section through a typical Nigerian casement window opening, showing frame, sill, lintel, and wall). Moves around the classroom, providing individual guidance, correcting errors, and answering questions. Reviews common mistakes observed and provides immediate feedback to the class. Ensures students are correctly labeling and dimensioning their drawings.
Student Activity: Works individually or in pairs to draw the assigned detail, applying the learned conventions and dimensions. Seeks assistance from the teacher as needed. Focuses on precision, correct line weights, and clear labeling and dimensioning.
Instruction: Students are to sketch and label the following details, assuming a scale suitable for clarity (e.g., 1:10 or 1:20 detail scale). Use typical Nigerian dimensions.
Question 1: Sketch and label a typical section of a strip foundation supporting a 225mm sandcrete block wall, showing the Damp Proof Course (DPC) and the finished ground level.
Solution 1: (Teacher to draw on whiteboard or provide handout) ``` | | | 225mm | | SANDCRETE | | WALL | | | |___________| <-- DPC (150mm above FGL) | | | WALL | | (Below) | |___________| | | | 225mm | | WALL | | | _______|___________|_______ <-- FINISHED GROUND LEVEL (FGL) / | | \ /________| |________\ | | | | | | CONCRETE | | | | FOUNDATION| | | | STRIP | | |_________|___________|_________| (Width: Wall thickness + 150mm each side = 225+150+150 = 525mm) | | (Depth: Typically 225mm - 300mm) |_________ EXCAVATION _________| | | |_______ GROUND ________| ``` Labels: 225mm Sandcrete Block Wall DPC (Damp Proof Course) Finished Ground Level (FGL) Concrete Foundation Strip (e.g., 525mm wide x 225mm deep) Ground
Commentary: This detail illustrates the basic components of a strip foundation. Emphasise the DPC placement above ground level to prevent rising damp and the typical dimensions used in Nigeria. --- Question 2: Draw a detailed section showing the ground floor construction of a residential building, from the hardcore up to the finished floor level. Include the Damp Proof Membrane (DPM) and a floor finish (e.g., ceramic tiles).
Solution 2: (Teacher to draw on whiteboard or provide handout) ``` __________________________ <-- CERAMIC TILE FINISH (10-15mm) |__________________________| | SCREED (25-50mm) | |__________________________| | REINFORCED CONCRETE SLAB | (100-150mm thick) |__________________________| | Damp Proof Membrane (DPM)| (Thick polythene sheet) |__________________________| | COMPACTED HARDCORE | (150-200mm thick) |__________________________| | COMPACTED EARTH | ``` Labels: Ceramic Tile Finish Screed (cement-sand mortar) Reinforced Concrete Slab Damp Proof Membrane (DPM) Compacted Hardcore Compacted Earth
Commentary: This showcases the layering involved in ground floor construction, essential for insulation and moisture control. Highlight the distinct layers and their functions. --- Question 3: Sketch an internal section of a wall showing a typical Nigerian louvre window, indicating the lintel above and the window sill below.
Solution 3: (Teacher to draw on whiteboard or provide handout) ``` | | | WALL | |_________| |_________| <-- REINFORCED CONCRETE LINTEL (e.g., 150mm deep) |_________| | | | WALL | | | | Window | | Frame | <-- WINDOW FRAME (TIMBER/ALUMINIUM) |_________| | \ \ \ \ | <-- GLASS LOUVRES | \ \ \ \| | \ \ \ \ | \ \ \ \ |_________| | | | WINDOW | <-- WINDOW SILL (EXTERNAL SLOPE) | SILL | |_________| | | | WALL | |_________| ``` Labels: Sandcrete Block Wall Reinforced Concrete Lintel Window Frame (Timber or Aluminium) Glass Louvres Window Sill (Internally usually flat, externally sloped)
Commentary: This detail specifically addresses a common window type in Nigeria. Emphasise the structural role of the lintel and the water-shedding function of the sill. --- Question 4: Draw a detailed section through the eaves of a gable roof with long-span aluminium sheeting, showing the wall plate, rafter, fascia board, and soffit board.
Solution 4: (Teacher to draw on whiteboard or provide handout) ``` \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ <-- LONG-SPAN ALUMINIUM SHEET \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \___________________________________________ | (PURLIN - often implied in rafter detail) | |___________________________________________| \ | | \| RAFT____R (e.g., 50x75mm timber) | / | /___________________________________________ | / \ | / \_______________________________________ | /_____| | | |_______________________________________| | (Wall plate bolted to wall - e.g., 50x100mm timber) |______________________________________________| | | | | | 225mm SANDCRETE BLOCK WALL | | | |______________________________________________| | | | FASCIA BOARD (e.g., 20x150mm timber) |_______|____________________________________ |_________|______________|______________| <- SOFFIT BOARD (e.g., 12mm plywood) |_________|______________|______________| |
Community Development and Self-Help Projects: In many Nigerian communities, self-help projects for building schools, clinics, or community halls are common. Knowledge of building details allows community members, artisans, or volunteers to better understand construction plans, identify appropriate materials, and ensure quality workmanship, leading to more resilient and functional community structures. For instance, understanding DPC ensures the building remains free from rising damp, a common issue impacting health and structural integrity.
Property Valuation and Home Ownership: Aspiring homeowners or those wishing to renovate their homes can use this knowledge to critically assess the quality of construction, identify structural components that might need attention (e.g., cracks in lintels, sagging roof rafters), and communicate effectively with contractors. This empowers individuals to make informed decisions about their investments and ensures they get value for money, preventing exploitation by unscrupulous builders.
Environmental and Climate Resilience: Nigeria faces various environmental challenges, including heavy rainfall, heat, and sometimes flooding. Understanding roof details (eaves, gutters, roof pitch) helps in designing for efficient rainwater harvesting and proper drainage. Knowledge of foundation types and DPM application is crucial in flood-prone areas to protect buildings from moisture damage. Similarly, window details (e.g., louvre windows) are vital for passive ventilation to mitigate heat in tropical climates, reducing reliance on energy-intensive air conditioning. This connects the technical drawings to practical, sustainable living in the Nigerian context.