Lesson Notes By Weeks and Term v5 - Grade 11
Civil drawing: foundational plans and elevations – Week 7 focus
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Civil drawing: foundational plans and elevations – Week 7 focus
Download the Lessonotes Mobile South Africa app for faster lesson access on Android and iPhone.
Subject: Engineering Graphics and Design
Class: Grade 11
Term: 2nd Term
Week: 7
Theme: General lesson support
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This week, we delve into the foundational plans and elevations that are crucial components of civil drawings. Civil drawings form the backbone of any construction project, providing a visual representation of proposed structures and infrastructure. Specifically, foundational plans and elevations illustrate the layout and vertical dimensions of the foundation, which is the most important part of any building, ensuring its structural integrity. Understanding these drawings is essential for various professionals, including architects, engineers, construction workers, and even city planners.
2.1 Foundation Plan: The Bird's Eye View A foundation plan is a horizontal section taken through the building at the level of the foundation. It's essentially a "map" of the foundation, showing the outline of the building, the location of walls, columns, footings, and any other relevant structural elements.
Key features to look for include: Footings: These are the widened bases of walls or columns that distribute the load of the structure over a larger area of soil. Common types include strip footings (for walls) and pad footings (for columns).
Walls: Foundation walls support the above-ground structure and prevent soil from entering the building. They can be concrete, brick, or block.
Columns: Vertical structural members that transfer loads from the roof and floors down to the foundation.
Reinforcement: Steel bars (rebar) embedded in the concrete to increase its tensile strength. Reinforcement details are crucial for structural integrity.
Dimensions: Accurately indicate the size and location of all elements.
Grid Lines: A network of lines used as a reference system for locating elements on the plan.
Notes and Specifications: Provide additional information about materials, construction methods, and other important details.
Damp-proofing membrane: A waterproofing layer applied to the exterior of the foundation wall to prevent moisture penetration. 2.2 Foundation Elevation: The Side View A foundation elevation is an orthographic projection showing the vertical appearance of the foundation. It shows the height of the foundation walls, the ground level, and any steps or changes in elevation. It complements the foundation plan by providing vertical dimensions and information.
Key features include: Ground Level (GL): The existing surface of the ground.
Top of Foundation (TOF): The height of the foundation wall above the ground level.
Bottom of Footing (BOF): The depth of the footing below the ground level.
Wall Height: The vertical distance from the BOF to the TO
F. Steps or Changes in Elevation: Show variations in the foundation height due to sloping ground or different floor levels.
Damp-proofing: Its vertical extent above the ground level. 2.3 Common Symbols and Abbreviations: R/F: Reinforcement C/C: Centre to Centre (spacing) Ø: Diameter E
Q. SP.: Equally Spaced GL: Ground Level TOF: Top of Foundation BOF: Bottom of Footing CONC.: Concrete B/F: Building Line Specific symbols will vary depending on the drawing standards used (e.g., SANS 10160). Always refer to the drawing's legend. 2.4 Concrete Volume Calculation: Calculating concrete volume is essential for estimating material costs and planning construction.
The formula is simple: Volume = Length x Width x Height For footings, calculate the volume of each section separately and then add them together. Be sure to use consistent units (e.g., meters).
Example 1: Simple Foundation Plan and Elevation Imagine a small, rectangular building in a township, measuring 6m x 4m. We want to draw a basic foundation plan and elevation.
Foundation Plan: Draw the outline of the building: A rectangle measuring 6m x 4m to the specified scale (e.g., 1:50).
Add foundation walls: Draw the foundation walls inside the building outline, typically 230mm or 345mm thick (common brick wall thicknesses in South Africa).
Draw strip footings: Extend the foundation walls outwards on both sides to create the footings. The footing width is usually determined by the soil bearing capacity and the load of the building. Let's assume a 600mm wide footing.
Therefore, the footing extends 185mm on either side of a 230mm wall.
Add reinforcement details: Show the location of reinforcing steel within the footing and wall. This will typically be noted (e.g., Y12 @ 200mm C/C, meaning 12mm diameter rebar spaced 200mm apart).
Add dimensions: Include overall dimensions, wall thicknesses, footing widths, and footing projection from the wall face. Indicate the damp-proofing membrane location Foundation Elevation: Establish Ground Level (GL): Draw a horizontal line representing the ground level.
Draw the foundation wall: A rectangle extending upwards from the footing. The height of the wall depends on the design, but let's assume 600mm above ground level.
Draw the footing: A rectangle extending downwards from the foundation wall. Assume the footing is 300mm deep.
Label key elements: Label the GL, TOF, and BO
F. Add dimensions: Indicate the overall height of the foundation (TOF to BOF) and the height above ground. Indicate the damp-proofing membrane location Example 2: Concrete Volume Calculation Using the dimensions from Example 1, let's calculate the volume of concrete needed for the foundation walls and footings. Assume wall thickness is 230mm (0.23m) and footing width is 600mm (0.6m) and footing depth is 300mm (0.3m). Wall height from top of footing is 900mm (0.9m).
Calculate the length of the walls: The total length of the external walls is (6m + 4m) x 2 = 20m.