Class: Senior Secondary School 1 (SSS 1)
Term: 2nd Term
Week: 7
Age: 15 years
Duration: 45 minutes
Subject: Carpentry And Joinery
Curriculum Theme: Entrepreneurship Trade Subjects
Previous Lesson: Timber Seasoning and Defect Prevention.
Topic: TIMBER – Timber Preservation
Subject Matter: Methods of timber preservation, chemical treatment, painting and oiling, protection against insects.

Specific Objectives

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

Cognitive Domain:

Define timber preservation.
State at least three reasons for preserving timber.
List different methods of timber preservation.
Explain chemical treatment, painting, and oiling as methods of preservation.

Affective Domain:

Appreciate the importance of preserving timber for durability.
Value the economic benefits of timber preservation.

Psychomotor Domain:

Sketch examples of materials used for timber preservation.
Identify samples of preserved timber.

Participate actively in class discussions about timber preservation techniques.

Reference Materials

The following resources were used in planning this lesson:

9 Years Basic Education Curriculum for Basic Technology.
State Unified Scheme of Work for Senior Secondary Schools.
Basic Woodwork for Senior Secondary Schools by A.O. Okoro.
Charts showing different timber preservation methods.

Instructional Materials

The teacher will teach this lesson with the aid of:

Various timber preservatives (e.g., small samples of creosote, wood oil).
Charts illustrating methods of timber preservation.
Samples of untreated and treated timber.
Whiteboard/chalkboard and markers/chalk.

Rationale for the Lesson

This lesson helps pupils understand how to protect timber from damage, making it last longer. It is important because it teaches practical skills that reduce waste and save money in construction and woodworking projects, which is relevant to their daily lives and future careers.

Prerequisite/Previous Knowledge

Pupils are assumed to have prior knowledge of what timber is, its various uses, and some common problems associated with untreated wood.

Lesson Content/Board Summary

TIMBER PRESERVATION

Definition of Timber Preservation

Timber preservation refers to the process of treating wood to protect it from agents of deterioration such as insects, fungi, and adverse weather conditions. This process helps to extend the lifespan and usefulness of timber.

Reasons for Timber Preservation

Timber is preserved for the following reasons:

To protect timber from fungal decay (rot).
To prevent attack by insects like termites, wood borers, and beetles.
To increase the durability and lifespan of timber.
To improve the resistance of timber to fire.
To enhance the appearance of timber.
To reduce maintenance costs over time.

Methods of Timber Preservation

There are various methods used to preserve timber. These include:

1. Chemical Treatment

This method involves applying chemical preservatives to timber to protect it from biological agents of decay. Common chemical treatments include:

Pressure Impregnation: Timber is placed in a pressure cylinder where preservatives are forced deep into the wood fibres under high pressure.
Brushing/Spraying: Preservative liquids are applied to the timber surface using brushes or sprayers. This method offers less penetration compared to pressure treatment.
Dipping: Timber is immersed in a tank containing preservative chemicals for a specified period, allowing for better absorption than brushing.

Examples of chemical preservatives include Creosote, Copper-Chrome-Arsenate (CCA), Borates, and Permethrin.

2. Painting and Oiling

Painting and oiling are surface treatments that provide a protective barrier against moisture, sunlight, and minor insect attacks. They also enhance the aesthetic appeal of timber.

Painting: Involves applying layers of paint to the timber surface. Paint forms a protective film that prevents water absorption, guards against UV damage, and deters some insects.
Oiling: Involves applying natural or synthetic oils (e.g., linseed oil, teak oil) to penetrate the timber surface, enhancing its natural colour, providing water resistance, and preventing drying out.

3. Protection Against Insects

While chemical treatments are highly effective, other methods also help protect against insects:

Termite Shields: Metal barriers installed in foundations to prevent termites from reaching timber structures directly.
Proper Seasoning: Drying timber properly reduces its moisture content, making it less attractive to some insects and fungi.
Ventilation: Ensuring good airflow around timber structures helps prevent moisture build-up, which discourages fungal growth and insect infestation.
Borate Treatment: Borate salts can be applied to timber to provide insecticidal and fungicidal properties, often used in conjunction with other methods.

Teaching Methods/Instructional Techniques

Discussion, Lecture, Demonstration, Question and Answer, Visual Aids

Instructional Procedures

Step 1: Introduction

Time: 5 minutes
Teaching Skill: Set Induction
Teacher’s Activity: The teacher greets the pupils and reminds them about the previous lesson. The teacher then asks pupils to mention some common uses of timber and what problems timber users sometimes face (e.g., rot, insect attack). The teacher introduces the topic of timber preservation as a solution to these problems.
Pupils’ Activity: Pupils respond to questions and listen attentively.
Learning Point: Pupils are prepared for the lesson and can relate the topic to previous knowledge and real-life scenarios.

Step 2: Definition of Timber Preservation

Time: 7 minutes
Teaching Skill: Explanation/Definition
Teacher’s Activity: The teacher explains the meaning of timber preservation, emphasizing its purpose of extending timber’s lifespan. The teacher writes the definition on the board.
Pupils’ Activity: Pupils listen, take notes, and ask questions for clarification.
Learning Point: Pupils understand the basic concept and purpose of timber preservation.

Step 3: Reasons for Timber Preservation

Time: 7 minutes
Teaching Skill: Listing/Discussion
Teacher’s Activity: The teacher leads a discussion on why it is important to preserve timber, guiding pupils to state reasons such as protection from decay, insects, and increased durability. The teacher lists these points on the board.
Pupils’ Activity: Pupils contribute ideas, discuss, and copy notes from the board.
Learning Point: Pupils identify and understand the benefits of preserving timber.

Step 4: Chemical Treatment Methods

Time: 7 minutes
Teaching Skill: Explanation/Demonstration
Teacher’s Activity: The teacher explains chemical treatment as a method of preservation. The teacher describes methods like pressure impregnation, brushing, spraying, and dipping, using charts or diagrams if available. The teacher mentions examples of chemical preservatives.
Pupils’ Activity: Pupils listen, observe the charts, and take notes. Some pupils may sketch the application methods.
Learning Point: Pupils learn about chemical methods and types of preservatives used for timber.

Step 5: Painting and Oiling Methods

Time: 7 minutes
Teaching Skill: Explanation/Visualisation
Teacher’s Activity: The teacher explains painting and oiling as surface preservation methods. The teacher discusses how these methods protect timber from moisture and sunlight and enhance appearance. The teacher may show samples of painted or oiled wood.
Pupils’ Activity: Pupils pay attention, ask questions, and make notes on the characteristics of these methods.
Learning Point: Pupils understand how surface treatments contribute to timber preservation.

Step 6: Protection Against Insects

Time: 5 minutes
Teaching Skill: Elaboration/Illustration
Teacher’s Activity: The teacher elaborates on specific ways to protect timber against insects, including physical barriers like termite shields, the importance of proper seasoning, and good ventilation. The teacher emphasizes that these often complement chemical treatments.
Pupils’ Activity: Pupils listen and note additional methods of insect protection.
Learning Point: Pupils learn about various strategies for protecting timber, especially from insect damage.

Step 7: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

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

Define timber preservation.
State three reasons why timber is preserved.
Mention two chemical methods of timber preservation.
Explain how painting helps to preserve timber.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 2 minutes
Teaching Skill: Summarization
Teacher’s Activity: The teacher summarizes the key points of the lesson, reiterating the importance of timber preservation for durability and economic benefits. The teacher assigns homework: “List five common timber preservatives and their uses.”
Pupils’ Activity: Pupils listen to the summary and copy down the homework.
Learning Point: Pupils consolidate their learning and are given an opportunity for further study.

Lesson Keywords

Timber – Wood that has been processed for structural or other purposes.
Preservation – The act of keeping something in its original state or in good condition.
Chemical Treatment – The application of chemicals to timber to protect it from decay and pests.
Painting – Applying a coating of paint to timber for protection and aesthetics.
Oiling – Applying oil to timber to protect, nourish, and enhance its appearance.
Fungi – Microorganisms that cause decay in timber.
Termites – Social insects that feed on wood, causing significant damage.

Differentiation

For pupils who grasp concepts quickly, the teacher can encourage them to research different types of chemical preservatives and their environmental impacts. For those needing more support, the teacher can provide simplified notes and focus on identifying key methods through visual aids and practical examples.

Note for teachers using this lesson plan

Teachers should ensure to bring actual samples of treated and untreated timber, if possible, to enhance practical understanding. Emphasize safety precautions when discussing chemical treatments. Encourage pupils to relate the lesson to carpentry projects in their communities.