Lesson Notes By Weeks and Term v3 - Senior Secondary 3
Construction of Simple Block / Brick Walls
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Construction of Simple Block / Brick Walls
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Subject: Block laying, Brick laying & Concrete Works
Class: Senior Secondary 3
Term: 2nd Term
Week: 1
Theme: Blocklaying / Bricklaying
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Students should be ableto:In terpret block and brick wall from aworking drawing. Sketch fixing of doorand window frames at construction stage and the completion of construction Distinguish betweenpointing and jointingand sketch differenttypes in wallconstruction.
This section provides a detailed explanation of the core concepts related to the construction of simple block/brick walls, essential for the teacher's comprehensive understanding and delivery. This section outlines practical, teacher-led and student-centred activities to facilitate learning.
Teacher Activities: Introduction (10 minutes): Display various working drawings of simple buildings (floor plans, sections, elevations relevant to Nigerian housing). Initiate a brief discussion on the importance of accurate masonry work in preventing structural failures and ensuring durability in the local context. Explanation of Working Drawing Interpretation (15 minutes): Using visual aids (projected drawings or large printouts), explain standard symbols for walls, doors, windows, and common scales (e.g., 1:100, 1:50). Demonstrate how to locate wall dimensions, door openings (width, height), and window positions/sizes on a drawing. Highlight the interpretation of different hatching patterns for concrete blocks and bricks.
Explanation of Frame Fixing (20 minutes): Present diagrams or real-life photographs/models of door and window frames, specifically showing holdfasts/lugs. Describe step-by-step the process of fixing frames during construction and at completion, emphasizing plumbing, levelling, and bracing. Show how holdfasts are embedded in mortar joints and how alternative fixing methods (bolts, screws, rawlplugs) are used in finished walls. Emphasize the role of lintels and sills. Explanation of Pointing and Jointing (20 minutes): Clearly define and distinguish between jointing and pointing, using real-world examples or analogies relevant to Nigerian construction practices (e.g., exposed brick walls in some modern buildings). Present visual examples or sketches of different joint profiles (flush, struck, weathered, raked, concave, V-joint). Discuss the suitability of each joint type for internal vs. external walls, considering weather conditions in Nigeria. Practical Demonstration / Visualisation (15 minutes): If possible, use actual blocks/bricks and a small frame model to demonstrate how a holdfast would be embedded. Show physical jointing tools or videos of masons performing different jointing techniques. Guided Practice Facilitation (Remainder of class): Guide students through interpreting a simple drawing provided. Supervise sketching activities, offering individual feedback and correction.
Student Activities: Working Drawing Interpretation (Interactive): Students study provided simple working drawings of a typical Nigerian dwelling (e.g., a one-bedroom self-contained unit plan). Students identify and mark wall types, door positions and widths, and window positions and sizes on their copies or worksheets. Students answer questions related to the drawing's dimensions and features.
Sketching Door/Window Frames: Students individually sketch (or in pairs) the fixing details of a timber door frame at the construction stage, showing holdfasts. Students then sketch the fixing details of an aluminum window frame at the completion of construction, showing fixing screws/rawlplugs and sealant. Students label all key components in their sketches. Distinguishing Pointing/Jointing and Sketching Joints: Students write down the key differences between pointing and jointing in their notebooks. Students sketch at least three different types of mortar joints (e.g., flush, weathered, concave), clearly showing the profile of the mortar between two block/brick units.
Class Discussion/Q&A: Students ask questions about unclear concepts or techniques. Students share their interpretations and sketches for peer review and teacher feedback. This section provides scaffolded questions with detailed solutions to reinforce learning.
Question 1: Working Drawing Interpretation Observe the simplified partial floor plan for a building in Minna, Niger State, shown below (imagine a simple rectangle representing a room). A wall segment has a total length of 3000mm. A doorway `D1` is centrally placed along this segment, with a width of 900mm. Two windows `W1` are to the left of the door, each 600mm wide, separated by a 450mm block pier.
The scale of the drawing is 1:
5
0. Task: a) Calculate the actual length (in meters) of the entire wall segment. b) Determine the width of the solid wall portion (blockwork) on either side of the door opening. c) Calculate the distance on the drawing (in mm) that represents the 900mm wide doorway.
Solution 1: a)
Actual length of the entire wall segment: Given length = 3000mm.
To convert to meters: 3000mm / 1000 = 3 meters.
Answer: The actual length of the entire wall segment is 3.0 meters. b) Width of the solid wall portion on either side of the door opening: Total wall length = 3000mm. Door width = 900mm. Total solid wall on both sides = Total wall length - Door width = 3000mm - 900mm = 2100mm. Width of solid wall on one side = 2100mm / 2 = 1050mm.
Answer: The width of the solid wall portion on either side of the door opening is 1050mm. c) Distance on the drawing for the 900mm wide doorway: Drawing scale is 1:
5
0. This means 1 unit on the drawing represents 50 units in reality. Drawing distance = Actual distance / Scale factor = 900mm / 50 = 18mm.
Answer: The 900mm wide doorway would be represented by 18mm on the drawing. --- Question 2: Sketching Door Frame Fixing (Construction Stage)
Task: Sketch a cross-section showing how a timber door frame jamb is typically fixed into a 150mm concrete block wall during the construction stage. Ensure to label the frame jamb, concrete blocks, mortar joints, and the holdfast.
Solution 2: (Teacher to draw a clear diagram on the board or provide a handout) ``` _______________________ | | | (Unfinished Block) | |_______________________| | | <- Mortar Joint | | |_______/ /_____________| <- Concrete Block (150mm thick) | / | <- Holdfast (bent and embedded) |_______/_______________| | | <- Timber Door Frame Jamb (e.g., 50x100mm) | | (Frame is plumbed and braced) | | |_______/_______________| | | | (Unfinished Block) | |_______________________| | | <- Mortar Joint |_______/ /_____________| <- Concrete Block (150mm thick) | / | <- Holdfast (bent and embedded) |_______/_______________| ```
Commentary: The sketch clearly illustrates the timber frame jamb secured by galvanized steel holdfasts, which are embedded within the horizontal mortar joints of the blockwork as the wall is built. The blockwork is shown in its unfinished state. --- Question 3: Sketching Window Frame Fixing (Completion Stage)
Task: Sketch a cross-section showing an aluminum window frame fixed into a finished (plastered) 225mm brick wall, representing the completion of construction. Label the window frame, brick wall, plaster finish, fixing screws/plugs (rawlplugs), and sealant.
Solution 3: (Teacher to draw a clear diagram on the board or provide a handout) ``` ___________________________________________ | | | Plaster finish | |___________________________________________| | | | Brick Wall (225mm thick) | | ____________________________ | | | | | | | Aluminum Window Frame |-------| <- Fixing screw/plug (rawlplug) | | (Profile) | | | |____________________________| | | | Plaster finish | | | | | | | |____________________________|-------| <- Fixing screw/plug (rawlplug) | Sealant bead | |___________________________________________| | | | Plaster finish | |___________________________________________| ```
Commentary: The sketch shows the aluminum window frame installed within a finished opening in a brick wall. The wall has a plaster finish. The frame is secured to the wall reveals using screws and rawlplugs, and the gaps are sealed with a sealant bead, indicating a complete installation. --- Question 4: Distinguish between Pointing and Jointing * Task: Explain the primary difference between "pointing" and "jointing" in block/brick wall construction. | | | | |____________________________|-------| <- Fixing screw/plug (rawlplug) | Sealant bead | |___________________________________________| | | | Plaster finish | |___________________________________________| ```
Commentary: The sketch shows the aluminum window frame installed within a finished opening in a brick wall. The wall has a plaster finish. The frame is secured to the wall reveals using screws and rawlplugs, and the gaps are sealed with a sealant bead, indicating a complete installation. --- Question 4: Distinguish between Pointing and Jointing Task: Explain the primary difference between "pointing" and "jointing" in block/brick wall construction.
Solution 4: Jointing: This is the process of compacting and shaping the mortar joints as the wall is being built, while the mortar is still fresh. Its main purpose is to make the mortar denser for better weather resistance and to give a neat, uniform appearance to the newly laid masonry. It's an integral part of the initial laying process.
Pointing: This is the process of raking out a portion of old or damaged mortar from the joints of an existing wall and then filling these joints with fresh, often richer, mortar. It is typically done for repair, to improve weather protection of an old wall, or for decorative purposes on already constructed masonry. It's a separate operation performed after the wall is built.
Key Difference: Jointing is done during construction with fresh mortar; Pointing is done after construction on existing walls (often with old mortar removed first) for repair or aesthetic enhancement. --- Question 5: Sketch Two Types of Jointing Task: Sketch cross-sections of two distinct types of mortar joints, showing how the mortar profile differs. Label each type.
Solution 5: (Teacher to draw clear diagrams on the board or provide a handout)* Type 1: Weathered Joint ``` _______________________ | | | (Block/Brick) | |_______________________| | \ \ \ \ \ \ \ \ \ \ \ | <- Mortar Joint (slopes outwards/downwards) | \ \ \ \ \ \ \ \ \ \ | | \ \ \ \ \ \ \ \ \ | |_______________________| | | | (Block/Brick) | |_______________________| ```
Commentary: The weathered joint is sloped downwards and outwards from the top, effectively shedding water away from the joint and wall surface, providing excellent weather protection.
Type 2: Concave (Bucket Handle) Joint ``` _______________________ | | | (Block/Brick) | |_______________________| | ( ) | <- Mortar Joint (curved inwards) | ( ) | | ( ) | |_______________________| | | | (Block/Brick) | |_______________________| ```
Commentary: The concave joint is formed by pressing the mortar inwards with a curved tool. This creates a dense, watertight joint with a neat, traditional appearance. ---
A working drawing shows a wall section with a dimension of `4500`. The drawing scale is `1:50`.
Interpretation: The actual length of the wall section is 4500mm (4.5 meters).
Application: If a student measures 90mm on the drawing, the actual length is 90mm 50 = 4500mm. Conversely, if a wall is 4.5m long, it would be drawn as 4500mm / 50 = 90mm on the drawing.
B. Sketching Fixing of Door and Window Frames
Proper fixing of door and window frames ensures structural stability, weatherproofing, and security. Frames can be fixed at various stages of construction.
Door Frame Fixing:
At Construction Stage:
Method: Timber or steel door frames are typically erected before or during the initial stages of wall construction. Holdfasts (galvanized steel or iron straps, usually 25x3mm to 30x5mm) are nailed/screwed to the frame at intervals (e.g., 600mm to 900mm vertically, 3 per jamb).
Process: As the block/brick courses are laid, the holdfasts are bent and embedded into the fresh mortar joints, tying the frame securely to the masonry. The frame must be plumbed, levelled, and adequately braced to prevent movement during wall construction.
Key components: Frame jamb, holdfast, mortar joint, block/brick wall, temporary bracing (e.g., timber props).
At Completion of Construction (or post-construction):
Method: This is less common for primary load-bearing walls but is used for partitions or when frames are installed later (e.g., steel security doors). Frames are often fixed using chemical anchors, expansion bolts, or plugs and screws directly into the finished masonry opening. The gap between the frame and the wall is then filled with mortar, grout, or sealant.
Key components: Frame jamb, finished wall (plastered/rendered), fixing bolts/screws with rawlplugs/chemical anchors, sealant/mortar infill.
Window Frame Fixing:
At Construction Stage:
Method: Similar to door frames, window frames (timber, steel, or aluminum with sub-frames) are typically set in place after the sill course is laid and before the lintel is installed. Holdfasts or metal lugs are attached to the frame (usually 2-3 per vertical jamb, and sometimes to the sill and head sections).
Process: The frame is plumbed, levelled, and temporarily braced. As the wall progresses upwards, the holdfasts/lugs are embedded into the mortar joints. The window opening will have a pre-cast concrete sill at the bottom and a pre-cast or in-situ concrete lintel at the top to support the masonry above.
Key components: Window frame, holdfast/lug, mortar joint, block/brick wall, window sill (concrete), lintel (concrete), temporary bracing.
At Completion of Construction:
Method: This is common for aluminum or uPVC window frames, which are often installed into pre-formed masonry openings after the wall is fully built and sometimes even plastered. A sub-frame (usually timber or steel) may be fixed first, or the window frame itself is fixed directly using screws and plugs (rawlplugs) into the reveal (sides of the opening). The gaps are then sealed with silicone sealant or mortar.
Key components: Window frame, finished wall (plastered/rendered), fixing screws/bolts with rawlplugs, reveal, sill, lintel, sealant.
Sketching Guidance for Frames:
Show a section through the wall at the jamb.
Clearly indicate the frame material, wall material, and the fixing mechanism (holdfasts, bolts).
Label all components.
For "construction stage," show unfinished masonry and the holdfasts embedded.
For "completion stage," show a finished (e.g., plastered) wall with the frame neatly installed and sealed.
C. Distinguishing Between Pointing and Jointing
These are finishing techniques for mortar joints in masonry, often confused but distinct in application and purpose.
Jointing:
Definition: The process of finishing the mortar joints as the wall is being constructed, before the mortar has fully set. It involves tooling the fresh mortar to a specific profile.
Purpose: Primarily to compress the mortar, making it denser and more weather-resistant, and to provide a neat, uniform appearance. It is an integral part of the bricklaying/blocklaying process.
Timing: Done immediately or shortly after laying the blocks/bricks.
Tools: Jointing tool (e.g., V-joint tool, concave jointer, bucket handle), trowel, straightedge.
Pointing:
Definition: The process of cutting out or raking back a portion of the original, often hardened, mortar from the joints of an existing wall and then filling these joints with fresh, often richer and more durable, mortar.
Purpose: Primarily for repair (e.g., when original mortar has deteriorated), for decorative purposes on exposed masonry, or to enhance the weather resistance of an old wall. It is a separate operation performed after the wall has been built and dried.
Timing: Done after the wall construction is complete, or much later as a remedial or aesthetic treatment.
Tools: Pointing trowel (small, pointed), hawk, chisel or raking tool (to remove old mortar), brush.
Understanding the construction of simple block/brick walls has significant practical relevance in the Nigerian context: Career Opportunities and Entrepreneurship: This knowledge forms the bedrock for various vocations within Nigeria's thriving construction industry. Students can pursue careers as skilled masons, bricklayers, site supervisors, draughtsmen, or even set up their own small building construction companies. Many Nigerian youth seek skills in masonry to build their own homes or offer services in their communities. Sustainable Housing and Community Development: Equipped with these skills, individuals can contribute to the construction of durable and affordable housing in their communities, particularly in rural and semi-urban areas where block/brick construction is prevalent. Proper frame fixing and joint finishing ensure longevity, reducing maintenance costs and promoting sustainable development efforts like the "housing for all" initiatives.
Quality Control and Inspection: Knowledge of proper construction techniques empowers individuals, including homeowners, to critically assess the quality of work performed by masons on their projects. This helps in ensuring that buildings meet required standards, preventing common issues like damp penetration due to poor jointing or insecure window frames, which are crucial considerations given Nigeria's diverse weather conditions.