Lesson Notes By Weeks and Term v3 - Senior Secondary 2
Sections
Download the Lessonotes Mobile Nigeria 2025 app for faster lesson access on Android and iPhone.
Sections
Download the Lessonotes Mobile Nigeria 2025 app for faster lesson access on Android and iPhone.
Subject: Building Construction
Class: Senior Secondary 2
Term: 2nd Term
Week: 1
Theme: Building Drawing
This page supports the lesson note with a companion video and a short classroom-ready summary.
For class groups and homework, share this lesson page so learners also get the summary, objectives, and full lesson context.
Draw types of sections through abuilding plan. In terpret sectioningthrough a givenplan. Produce sectioned part
tiles (e.g., Gerard tiles).
Fascia Board: Timber board covering the ends of the rafters at the eaves.
Soffit Board: Board covering the underside of the eaves.
Ceiling: Suspended ceiling (e.g., plasterboard, PVC, or T&G timber) or exposed roof structure.
Ground Level: Indicate the finished ground line. 2.
6. Step-by-Step Procedure for Drawing a Section To draw a section, students will typically need a building plan and at least one elevation.
Example Scenario: Drawing a cross-section (A-A) through a simple rectangular bungalow plan.
1. Preparation: Place the building plan on the drawing board. Place a blank sheet of drawing paper either directly below or to the side of the plan, depending on the section view required. For a vertical section (like A-A running horizontally on the plan), place the paper below. Align the plan and the drawing paper accurately using a T-square.
2. Projecting Key Points: Identify the section line (A-A) on the plan. From every point where the section line cuts through a wall, foundation, column, door, window, or any other internal feature, project vertical lines downwards (or across, if the paper is to the side) onto the drawing paper using a set square and T-square. These projection lines should be very light, construction lines. Also, project lines from the extreme ends of the building to define its overall width in section.
3. Establishing Ground and Floor Levels: Draw a thick horizontal line to represent the Finished Ground Level (FGL). Measure and draw the Damp Proof Course (DPC) level, typically 150mm above FGL, as a horizontal line. Measure and draw the Finished Floor Level (FFL), typically at the same level as DPC or slightly above. The distance from FGL to FFL is the plinth height.
4. Drawing Foundations: Below the FGL, measure the depth of the foundation (e.g., 600mm to 900mm below FGL for a strip foundation, depending on soil). Draw the concrete footing (e.g., 600mm wide x 225mm deep). Draw the blockwork/concrete stub wall extending from the footing up to the DPC level, aligning with the projected wall lines.
5. Drawing Walls: From the FFL, draw the vertical wall lines upwards, using the projected lines as guides. Measure and mark the Floor-to-Ceiling Height (e.g., 2.8m). Draw a horizontal line representing the ceiling level.
6. Drawing Windows and Doors (if cut through): If the section line passes through a window, project the width of the window opening. Measure the window sill height (e.g., 900mm from FFL) and the window head height (e.g., 2.1m from FFL). Draw these elements, including the lintel above. If a door is cut, show the door opening and the lintel above (usually at 2.1m from FFL).
7. Drawing the Roof Structure: From the wall plate level (which is usually at the floor-to-ceiling height), determine the pitch of the roof (e.g., 30 degrees). Draw the roof trusses, rafters, purlins, and wall plate according to standard details. Indicate the roof covering material. Show fascia board, soffit board, and any eaves projections.
8. Drawing the Ceiling: If there is a suspended ceiling, draw it at the ceiling level, showing the ceiling joists/suspension system.
9. Adding Internal Details and Hatching: Show floor finishes (screed, tiles). Indicate hardcore beneath the floor slab. Add hatching to concrete (dots/triangles) and masonry (diagonal lines) elements to denote materials. Show rendering/plaster on walls if applicable.
1
0. Dimensioning and Labelling: Add key vertical dimensions (e.g., FGL to DPC, FFL to ceiling, wall plate height, overall roof height). Label all major components (e.g., "Strip Foundation," "150mm Thick Hardcore," "DPC," "150mm RC Floor Slab," "225mm Sandcrete Wall," "Timber Roof Truss," "Aluminium Roofing Sheets," "PVC Ceiling").
1
1. Line Quality: Use appropriate line weights: thick for cut elements, medium for visible elements in the background, thin for projection lines and dimensions. 2.
1. Definition of a Section A section, in building construction drawing, is a view obtained by imagining a building or a part of it being cut through by a vertical plane. This imaginary cut exposes the internal construction, structural elements, and vertical relationships of different parts of the building. It essentially shows what the building would look like if it were sliced open from top to bottom. 2.
2. Purpose of Drawing Sections Sections are indispensable in building construction for several reasons: To Reveal Internal Details: They show the hidden parts of a building such as foundations, wall construction, floor slabs, ceiling heights, roof structures, lintels, and finishes.
To Show Vertical Dimensions: Sections provide clear indications of heights, such as floor-to-ceiling heights, window and door head/sill heights, wall plate level, and overall roof height.
To Indicate Materials and Components: They are used to specify different construction materials (e.g., sandcrete blocks, concrete, timber, roofing materials) and their assembly.
To Aid Construction: Artisans (e.g., masons, carpenters) rely heavily on sections to understand how different components connect and to ensure proper installation.
For Quantity Surveying: Essential for calculating quantities of materials for foundations, walls, roofs, etc. 2.
3. Types of Sections There are two primary types of sections commonly drawn: Longitudinal Section: This is a section taken along the longer dimension or length of a building. It often reveals a wider view of the building's internal layout, including multiple rooms and the main roof structure over the longest span.
Cross Section: This is a section taken across the shorter dimension or width of a building, usually perpendicular to the longitudinal section. It typically provides detailed views of specific rooms, wall thicknesses, and roof details across a narrower span. 2.
4. Section Lines and Their Interpretation On a building plan, the position of an imaginary cutting plane is indicated by a "section line." Appearance: A section line is represented by a thick dashed or chain line.
Arrows: Arrows are drawn at the ends of the section line to indicate the direction from which the section is viewed. This determines which part of the building is considered to be "removed" and which part is being shown.
Letters: Alphabetic letters (e.g., A-A, B-B) are placed at the ends of the section line to label the specific section. For instance, "Section A-A" refers to the view obtained by cutting along the line marked A-A. 2.
5. Elements to Show in a Section When drawing a section through a typical Nigerian bungalow, the following elements must be accurately represented: Foundation: Strip foundation (most common for bungalows), pad foundation, or raft foundation, showing the concrete footing and blockwork/concrete stub wall.
Hardcore: Layer of broken stones/laterite compacted below the floor slab.
Damp Proof Course (DPC): A waterproof layer (e.g., polythene sheeting or cement screed with waterproofing additive) placed horizontally in walls to prevent moisture rise from the ground.
Floor Slab: Concrete slab (e.g., 100-150mm thick) laid on the hardcore, often with a cement screed finish or tiles.
Walls: Show the thickness and material (e.g., 225mm or 150mm sandcrete blocks), plastering if applicable.
Door/Window Openings: Indicate lintels (reinforced concrete beams above openings), window sills, and specific details like the window frame.
Floor to Ceiling Height: Crucial vertical dimension, typically 2.7m to 3.0m for residential buildings in Nigeria.
Wall Plate: Timber plate laid on top of the wall, supporting the roof trusses.
Roof Structure: Trusses (timber or steel), rafters, purlins, and king/queen posts where applicable.
Roof Covering: Corrugated iron sheets, aluminium roofing sheets, or concrete roofing tiles (e.g., Gerard tiles).
Fascia Board: Timber board covering the ends of the rafters at the eaves.
Soffit Board: Board covering the underside of the eaves.
Ceiling: Suspended ceiling (e.g., plasterboard, PVC, or T&G timber) or exposed roof structure.
Ground Level: Indicate the finished ground line. 2.
6. Step-by-Step Procedure for Drawing a Section To draw a section, students will typically need a building plan and at least one elevation.
Example Scenario: Drawing a cross-section (A-A) through a simple rectangular bungalow plan.
1. Preparation: * Place the building plan 3.
1. Teacher Activities: Introduction (10 minutes): Begin by reviewing the concept of building plans and elevations from the previous week. Ask students what information is not clearly visible in a plan or elevation. Guide them towards internal structures and heights. Introduce "Sections" as the drawing type that reveals this missing internal information. Display simple examples of building plans with section lines and corresponding section drawings. Explanation and Demonstration (25 minutes): Clearly explain the definition and purpose of sections, using a simple sketch of a building cut in half. Explain the difference between longitudinal and cross-sections. Demonstrate how section lines are indicated on a plan (thick dashed line, arrows, letters), emphasizing the importance of the viewing direction. Using a prepared simple bungalow plan on the chalkboard/whiteboard or projector, perform a step-by-step live demonstration of drawing a cross-section: Projecting key lines from the plan. Establishing FGL, DPC, and FFL. Drawing foundation, walls, and openings. Adding roof structure and ceiling. Hatching and labelling. Emphasize accurate measurement and adherence to standard construction details common in Nigeria (e.g., 600x225mm strip foundation, 2.8m headroom, 150mm DPC height).
Guided Practice Introduction (15 minutes): Distribute a different, slightly more complex, but still manageable, bungalow plan to each student or group. Instruct students to identify section lines and interpret what they reveal. Guide students through the initial steps of drawing a specific section (e.g., a longitudinal section), focusing on projecting lines and establishing initial levels.
Circulation and Support (10 minutes): Move around the classroom, observing students' work, providing individual assistance, correcting misconceptions, and reinforcing proper drawing techniques. Address common errors observed during the demonstration or initial guided practice. Wrap-up and Homework Assignment (5 minutes): Summarize the key takeaways regarding sections. Assign independent practice questions for homework. 3.
2. Student Activities: Observation and Participation: Actively observe the teacher's demonstration of section drawing. Ask clarifying questions during explanations and demonstrations. Participate in discussions about the importance and interpretation of sections.
Guided Practice: Working individually or in pairs, students will attempt to draw a specified section (e.g., a cross-section) from a provided building plan under the teacher's guidance. Practice projecting lines, establishing ground and floor levels, and sketching major structural elements.
Discussion and Collaboration: Discuss interpretations of section lines and the types of information revealed. Share insights and challenge each other's understanding of various building components in section.
Independent Practice: Complete assigned section drawing tasks for homework or in-class individual work. 3.
3. Teaching and Learning Materials: Whiteboard/Chalkboard and markers/chalk Projector (if available) to display digital plans and sections Prepared overhead transparencies or large printouts of simple building plans with clear section lines. Large drawing T-square, set squares, pencils (HB, 2H), eraser for teacher's demonstration. Drawing boards, T-squares, set squares, pencils, drawing paper, metric rulers for students. Examples of finished section drawings (laminated or printed) for reference.
Optional: A simple physical model of a building that can be conceptually "cut" to show internal parts. FGL and draw a thinner horizontal line for DPC and FFL.
3. Draw Foundations: Below FGL, draw the concrete strip footing, 600mm wide and 225mm deep, centered under each wall line. The bottom of the footing will be 600mm below FG
L. From the footing, draw the 225mm blockwork stub wall up to the DPC level.
4. Draw Floor Structure: Between the stub walls, draw 150mm thick hardcore from the DPC level down to the FGL. Draw a 150mm thick RC floor slab on top of the hardcore, at FF
L. Add a thin line for cement screed/finish on top.
5. Draw Walls and Door: From FFL, draw the 225mm thick internal wall lines upwards. At the location of the door, draw the vertical door opening from FFL up to 2100mm. Draw a 225mm x 225mm reinforced concrete lintel spanning across the door opening, with its bottom at 2100mm above FF
L. Extend walls up to the wall plate level (2800mm above FFL).
6. Draw Roof Structure: At the wall plate level, draw the wall plate (e.g., 50x100mm timber). From the wall plate, draw the roof rafters at 30 degrees pitch, projecting out for eaves. Draw the ridge piece at the apex and purlins horizontally along the slope. Draw fascia and soffit boards at the eaves. Indicate corrugated aluminium roofing sheets on top of the purlins/rafters.
7. Draw Ceiling: At 2800mm above FFL, draw the PVC suspended ceiling, showing its support system.
8. Hatching and Labelling: Hatch all concrete elements (footing, lintel, slab) with dots/triangles. Hatch blockwork walls with diagonal lines.
Add key vertical dimensions: FGL to DPC, FFL to ceiling, lintel height, overall roof height.
Label all major components: "Strip Foundation", "Hardcore", "DPC", "RC Floor Slab", "225mm Sandcrete Wall", "RC Lintel", "Timber Roof Truss (or Rafters)", "Corrugated Aluminium Roof", "PVC Ceiling", "Fascia Board", "Soffit Board", "Finished Ground Level".
Commentary: This question directly assesses Objective 1 and
3. Students must accurately project from the plan, understand standard building components, and represent them in section with correct dimensions and hatching. --- Question 3: Drawing a Longitudinal Section (Section A-A) Draw a complete longitudinal section (A-A) through the given bungalow plan, showing all necessary construction details, dimensions, and labels.
Solution 3: (Teacher should draw this on a large board or provide a detailed handout. The following is a description of the steps and the resulting features.) Step-by-step Drawing Process (Similar to Q2, but for longitudinal view):
1. Project Lines: Place the drawing paper below the plan. From the section line A-A on the plan, project light vertical lines downwards from all wall intersections, the edges of the window opening, and the overall length of the building.
2. Draw Ground and Floor Levels: Draw a thick horizontal line for FG
L. Measure 150mm above FGL and draw a thinner horizontal line for DPC and FFL.
3. Draw Foundations: Below FGL, draw the concrete strip footing, 600mm wide and 225mm deep, centered under each wall line. The bottom of the footing will be 600mm below FG
L. From the footing, draw the 225mm blockwork stub wall up to the DPC level.
4. Draw Floor Structure: Between the stub walls, draw 150mm thick hardcore from the DPC level down to the FGL. Draw a 150mm thick RC floor slab on top of the hardcore, at FF
L. Add a thin line for cement screed/finish on top.
5. Draw Walls and Window: From FFL, draw the 225mm thick internal wall lines upwards. At the location of the window, draw the horizontal window sill at 900mm from FFL. Draw the window head (bottom of lintel) at 2100mm from FFL. Draw a 225mm x 225mm reinforced concrete lintel spanning across the window opening. Extend walls up to the wall plate level (2800mm above FFL).
6. Draw Roof Structure: At the wall plate level, draw the wall plate (e.g., 50x100mm timber). From the wall plate, draw the roof rafters at 30 degrees pitch, projecting out for eaves. Draw the ridge piece at the apex and
Construction Project Execution and Supervision in Nigeria: Application: Architects, structural engineers, and site supervisors in Nigeria rely on sections to communicate intricate details of a building's structure and materials to masons, carpenters, and other artisans. For example, a section drawing precisely shows the depth of a strip foundation required for a bungalow in Lagos' sandy soil or the type of roof truss system to withstand heavy rainfall in Enugu.
Integration: Students can visit local construction sites (if feasible and safe) to observe how artisans interpret drawings or interview local builders about the importance of section drawings in their daily work.
Material Estimation and Costing: Application: Quantity surveyors and builders use sections to accurately calculate the volumes of concrete for foundations and floor slabs, the number of blocks needed for walls up to roof level, and the quantity of timber or steel required for roof structures. This directly impacts the budget and cost analysis for construction projects in Nigeria, helping prevent over-expenditure or material shortages.
Integration: Students can be given a simple section drawing and tasked with calculating the volume of concrete for the foundation or the number of block courses for a wall, integrating basic mensuration skills into Building Construction. Building Plan Approval and Regulatory Compliance: Application: Local government planning authorities and development control agencies across Nigerian states (e.g., Ministry of Physical Planning and Urban Development in Abuja or Lagos State Planning Permit Authority) require detailed section drawings as part of building plan submissions for approval. These sections demonstrate compliance with building codes regarding foundation depth, structural integrity, ceiling heights, and fire safety.
Integration: Students can research local building codes in their state or community (e.g., minimum ceiling height for residential buildings) and compare them with the dimensions shown in standard section drawings. They can also discuss the implications of non-compliance with building regulations.