Soil Types, Bearing Capacity and Substructure Construction for SS 3

Class: SS 3
Term: First Term
Week: 4
Age: 16 years
Duration: 45 minutes
Subject: Block Laying, Brick Laying and Concrete Work
Curriculum Theme: Substructure Construction
Previous Lesson: Types of Bonds and Bonding Practical
Topic: SUB-STRUCTURE CONSTRUCTION
Subject Matter: Definition of soil; Types of soil; Bearing capacity of soil; Types of floors and methods of construction

Specific Objectives

By the end of the lesson, pupils/students should be able to:

Cognitive Domain

• Define soil in the context of construction.
• State and describe different types of soil.
• Explain the concept of soil bearing capacity.
• Identify various types of floors used in building construction.
• Describe the methods of constructing different types of floors.

Affective Domain

• Appreciate the importance of understanding soil properties in building design.
• Value the correct selection and construction of floor types for building stability.

Psychomotor Domain

• Sketch simple diagrams illustrating different floor types.
• Outline the practical steps involved in constructing a solid ground floor.

Social Domain

• Participate actively in discussions about soil types and floor construction.

Reference Materials

The following resources were used in planning this lesson:

• 2025 Revised 9 Years Basic Education Curriculum
• Relevant State Unified Scheme of Work
• Building Construction for Senior Secondary Schools, Book 3
• The HeadTeacher Scheme of work

Instructional Materials

The teacher will teach this lesson with the aid of:

• Charts showing different types of soil (e.g., clay, sand, gravel).
• Diagrams illustrating various floor types and their construction methods.
• Samples of different soil types (optional).
• Building plans or pictures showing substructure components.

Rationale for the Lesson

Understanding soil properties and bearing capacity is fundamental to ensuring the stability and safety of any building. Proper floor construction is also essential for the functionality and durability of a structure. This lesson provides students with the knowledge to make informed decisions in substructure construction.

Prerequisite/Previous Knowledge

Students should have a basic understanding of building materials and the general components of a building structure.

Lesson Content/Board Summary

SUB-STRUCTURE CONSTRUCTION

Definition of Soil

Soil, in construction, refers to the unconsolidated material on the earth’s surface, formed from weathered rocks and organic matter. It serves as the natural foundation bed upon which buildings are constructed.

Types of Soil

Different types of soil have varying properties that affect their suitability for construction:

1. Clay Soil: Composed of very fine particles, sticky when wet, hard when dry, and has poor drainage. It generally has a low bearing capacity and can be problematic due to swelling and shrinkage.
2. Silt Soil: Consists of particles finer than sand but coarser than clay. It feels smooth, has moderate drainage, and its bearing capacity is moderate.
3. Sand Soil: Characterised by coarse, gritty particles. It has good drainage properties and a high bearing capacity when well-compacted and confined.
4. Gravel Soil: Made up of the coarsest particles, larger than sand. It offers excellent drainage and possesses a very high bearing capacity, making it ideal for foundations.
5. Loam Soil: A mixture of sand, silt, and clay. While often good for agriculture, its bearing capacity for construction varies significantly depending on the proportions of its components.

Bearing Capacity of Soil

The bearing capacity of soil is its ability to support the loads imposed by a structure without undergoing excessive settlement or shear failure. It is a critical factor in foundation design.

Factors affecting bearing capacity include:

1. Type of Soil: Granular soils (sand, gravel) generally have higher bearing capacity than cohesive soils (clay, silt).
2. Density of Soil: Densely compacted soils can support heavier loads than loose soils.
3. Moisture Content: High moisture content, especially in cohesive soils, can significantly reduce bearing capacity.
4. Depth of Foundation: Deeper foundations often rest on more stable and stronger soil layers, increasing effective bearing capacity.
5. Presence of Groundwater: A high water table can reduce the effective stress in the soil, thereby lowering its bearing capacity.

Types of Floors

Floors are horizontal structural elements that provide a working surface, divide a building into stories, and transfer loads to supporting walls or columns.

1. Ground Floors:
   1. Solid Ground Floor: Constructed directly on a prepared ground surface, typically using concrete.
   2. Suspended Ground Floor: Elevated above the ground, creating a void or crawl space underneath. These can be made of timber or concrete.
2. Upper Floors:
   1. Timber Floor: Consists of timber joists supporting floorboards, commonly used in residential buildings.
   2. Concrete Floor: A reinforced concrete slab, which can be cast in-situ (on-site) or constructed using precast concrete units.

Methods of Floor Construction

Solid Ground Floor Construction

1. Site Preparation: Clear the site of vegetation, topsoil, and debris. Excavate the area to the required depth.
2. Hardcore Laying: Lay a layer of broken stones, concrete rubble, or gravel (typically 150-300mm thick) and compact it thoroughly to provide a stable base and prevent rising damp.
3. Blinding Layer: Apply a thin layer of lean concrete (e.g., 50mm thick) over the hardcore to create a smooth, level surface for subsequent layers.
4. Damp Proof Membrane (DPM): Lay a continuous, impermeable membrane (such as a heavy-gauge polythene sheet) over the blinding layer to prevent moisture from rising into the building.
5. Insulation (Optional): If thermal insulation is required, rigid insulation boards are laid over the DPM.
6. Concrete Slab: Cast a reinforced concrete slab (typically 100-150mm thick) over the DPM. Ensure proper compaction and curing to achieve desired strength.
7. Finishing: Apply a screed (a layer of cement and sand mortar) to level the surface, followed by the desired floor finish (e.g., tiles, carpet, wood flooring).

Suspended Concrete Floor Construction (e.g., for upper floors or suspended ground floors)

1. Formwork/Shoring: Erect temporary supports (formwork) using timber or steel to create the mould for the concrete slab at the desired height.
2. Reinforcement: Place steel reinforcement bars (rebars) within the formwork according to the structural design to provide tensile strength.
3. Concreting: Pour and compact the concrete into the formwork, ensuring it fills all spaces and encases the reinforcement.
4. Curing: Allow the concrete to cure properly by keeping it moist for several days, which is essential for it to gain full strength.
5. Striking Formwork: Remove the formwork after the concrete has gained sufficient strength to support itself.
6. Finishing: Apply a screed and the desired floor finish.

Timber Floor Construction (e.g., for upper floors)

1. Wall Plates: Fix timber wall plates (horizontal timbers) to the top of supporting walls to provide a level bearing surface for the joists.
2. Joists: Lay timber joists (horizontal structural members) across the span, resting on the wall plates, with appropriate spacing as per design.
3. Herringbone Strutting/Blocking: Install bracing between joists (either herringbone strutting or solid blocking) to prevent them from twisting, improve load distribution, and reduce vibration.
4. Floorboards: Nail or screw timber floorboards (tongue and groove or plain-edged) onto the top of the joists.
5. Finishing: The floorboards can be sanded, varnished, painted, or covered with other floor finishes like carpet or laminate.

Teaching Methods/Instructional Techniques

Discussion, Explanation, Demonstration, Question and Answer, Visual Aids, Guided Practice

Instructional Procedures

Step 1: Introduction

Time: 7 minutes

Teaching Skill: Recalling/Engaging

Teacher’s Activity: The teacher greets the students and asks them to recall what they learned about the basic components of a building structure in previous classes. The teacher then introduces the topic of “Substructure Construction” by explaining its importance as the base of any building.

Students’ Activity: Students respond to questions about building components and listen attentively to the introduction of the new topic.

Learning Point: Building foundation importance

Step 2: Definition of Soil

Time: 3 minutes

Teaching Skill: Explaining/Defining

Teacher’s Activity: The teacher defines soil in the context of construction, explaining it as the natural material supporting foundations.

Students’ Activity: Students listen and contribute to the definition, asking questions for clarity.

Learning Point: Soil definition

Step 3: Types of Soil

Time: 5 minutes

Teaching Skill: Listing/Describing

Teacher’s Activity: The teacher uses charts to state and describe different types of soil (clay, silt, sand, gravel, loam), highlighting their key properties relevant to construction.

Students’ Activity: Students observe the charts, name types of soil, and note their characteristics.

Learning Point: Soil classification

Step 4: Bearing Capacity of Soil

Time: 5 minutes

Teaching Skill: Explaining/Illustrating

Teacher’s Activity: The teacher explains the concept of soil bearing capacity and discusses the factors that affect it, such as soil type, density, and moisture content.

Students’ Activity: Students listen, ask questions about bearing capacity, and discuss its importance.

Learning Point: Soil strength

Step 5: Types of Floors

Time: 5 minutes

Teaching Skill: Classifying/Visualising

Teacher’s Activity: The teacher explains what floors are in construction and classifies them into ground floors (solid, suspended) and upper floors (timber, concrete), using diagrams.

Students’ Activity: Students identify different types of floors from diagrams and ask questions about their uses.

Learning Point: Floor categories

Step 6: Methods of Floor Construction

Time: 15 minutes

Teaching Skill: Demonstrating/Detailing

Teacher’s Activity: The teacher describes the step-by-step methods of constructing a solid ground floor, a suspended concrete floor, and a timber floor, using diagrams or sketches to illustrate the processes.

Students’ Activity: Students pay close attention to the construction steps, observe the diagrams, and ask for clarifications on specific procedures.

Learning Point: Floor construction steps

Step 7: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

1. Define soil in the context of building construction.
2. Mention three types of soil and one characteristic for each.
3. What is meant by the bearing capacity of soil?
4. List two types of ground floors and two types of upper floors.
5. Describe two key steps in constructing a solid ground floor.

Students’ Activity: Students answer orally and in writing.

Learning Point: Substructure understanding

Step 8: Note-Taking

Time: 4 minutes

Teaching Skill: Guided Writing

Teacher’s Activity: The teacher guides students to copy the essential Board Summary notes on soil definition, types, bearing capacity, floor types, and construction methods into their notebooks.

Students’ Activity: Students copy the notes carefully into their notebooks.

Learning Point: Key concepts recorded

Step 9: Conclusion

Time: 1 minute

Teaching Skill: Summarising

Teacher’s Activity: The teacher briefly summarises the importance of understanding soil properties and proper floor construction for the stability and durability of buildings, reiterating that these form the critical substructure.

Students’ Activity: Students listen and reflect on the main points of the lesson.

Learning Point: Substructure construction importance

Continuous Assessment/Further Study

Type: Homework/Project

Instruction: Research and describe the typical soil conditions found in your local community. Suggest suitable foundation and floor types that would be appropriate for these conditions.

1. Identify at least two common soil types in your area.
2. Describe their general properties (e.g., drainage, stability).
3. Based on these soil types, recommend a suitable foundation type (e.g., strip, raft, pile).
4. Suggest an appropriate ground floor construction method for your local conditions.
5. Present your findings in a short report or a diagrammatic sketch.

Lesson Keywords

• Soil – Unconsolidated material on earth’s surface forming foundation bed.
• Bearing Capacity – Soil’s ability to support structural loads.
• Ground Floor – Floor resting directly on or suspended above the ground.
• Upper Floor – Floor above the ground level.
• Hardcore – Layer of broken stones beneath a ground floor slab.
• DPM – Damp Proof Membrane, a barrier against moisture.
• Formwork – Temporary mould for concrete.
• Joists – Horizontal timber members supporting floorboards.

Differentiation

For weaker learners, the teacher will provide simplified diagrams and focus on identifying the main types of soil and floors, offering more direct guidance during note-taking. For faster learners, the teacher will encourage them to research specific examples of local building projects and how soil conditions influenced their design, or to investigate advanced floor construction techniques like pre-stressed concrete floors.

Suggested Lesson Videos

For further understanding, students can search on YouTube for:

• “Types of soil for construction”
• “Soil bearing capacity explained”
• “Solid ground floor construction steps”
• “Suspended concrete slab construction”
• “Timber floor construction details”

Teacher Guide for Using This Lesson Plan

Before the lesson, ensure you have prepared charts or diagrams illustrating different soil types, floor types, and their construction methods. If possible, bring small samples of local soil types (clay, sand, gravel) for students to feel and observe. Begin by engaging students with questions about building foundations to activate prior knowledge. Systematically present the definitions, classifications, and construction processes as outlined in the Board Summary. Encourage students to ask questions and participate in discussions to deepen their understanding. When discussing construction methods, use visual aids to make the steps concrete and easy to follow. Ensure all students understand the importance of each stage, especially the DPM for solid ground floors. Guide students to copy the Board Summary notes after the main teaching points have been covered and evaluated. Pay attention to students who may struggle with technical terms, providing additional explanations or simpler analogies. Challenge faster learners with questions that require critical thinking about material selection or design considerations based on soil conditions. Conclude by reinforcing the critical role of substructure in overall building integrity.