4.2b Timber

• Techniek
• HBO
• Studiejaar 4

4.2B TIMBER

Understanding Timber

Learning Objectives

At the end of the lesson you will understand the environmental impact of using timber as a building material. At the end of the lesson you will be able to distinguish between softwood and hardwood cell structure. At the end of the lesson you will comprehend the importance of moisture content and seasoning in timber. At the end of the lesson you will recognize common defects that can occur in timber and how they can be prevented. At the end of the lesson you will be able to identify the characteristics of natural timber and different types of trees it comes from. At the end of the lesson you will understand the properties and uses of man-made timbers. At the end of the lesson you will know the reasons for treating and finishing timber. At the end of the lesson you will be familiar with the processes of timber recycling and reforestation.

What do you already know about timber as a building material?

The Environmental Considerations of Using Timber

Timber is a renewable building material with a lower environmental impact compared to steel or concrete. Deforestation remains a concern.

The Structure of Natural Timber

Includes cellulose fibers and lignin. Softwood from coniferous trees, hardwood from deciduous trees.

Moisture Content and Seasoning

Moisture content affects utility, reduced through seasoning methods like air-drying

Moisture Content and Seasoning

Moisture content affects utility, reduced through seasoning methods like  kiln-drying.

Common Defects in Timber

Warping, bowing, cupping, twisting, knots can occur if moisture content is not properly controlled.

Characteristics and Types of Natural Timber

Hardwoods from deciduous trees, softwoods from coniferous trees.

Hardwood trees: The wood from a deciduous (broadleaved) tree. includes eucalyptus, elm, maple, oak, and beech.

Softwood trees: The wood from a coniferous (evergreen) tree.

includes are pine, cedar, and cypress

Characteristics of natural timber

Tensile Strength: The tensile strength of natural timber is greater along the grain than across the grain.

Resistance to damp environments: is very resistant.

Longevity: Hardwoods very good. Softwoods good.

Aesthetic properties: natural colours range (red, purple, cream and brown). The grain can add to its aesthetics.

Properties and Uses of Man-Made Timbers

Plywood, particle board, MDF, with varied properties and applications.

Characteristics of man-made timber

Tensile strength: depends on the man-made timber

• Plywood – high tensile strength in all directions
• Particle board and MDF – very low

Resistance to damp environments: depends on the man-made timber.

Exterior plywood – excellent.

Interior plywoods very low

Particle board and MDF – very low

 Longevity:

• Plywood is high
• Particle board and MDF is low to medium
• Aesthetic properties:
• Plywood if the top layer is of a nice timber like Beech will be good
• Particle board and MDF requires finishing or a sheet of lamination (see previous section)

Treating and Finishing Timber

Enhances resistance to insects, fungus, and weather. Staining and sanding improve aesthetics.

Timber Recovery, Recycling, and Reforestation

Essential for sustainability and environmental impact.

Key Definitions

Softwood, Hardwood, Moisture content, Seasoning, Kiln-drying, Air-drying, Warping, Bowing, Cupping, Twisting, Knots, Plywood, Particle Board, MDF, Lamination, Creosote, Reforestation

Find a image (or take a image) or man made wood / engineered wood

Take a image or find a image of soft wood.

Find or take a image of hard word

Explain how your desk is made.

Write down 3 things you learned in this lesson.

Have students enter three things they learned in this lesson. With this they can indicate their own learning efficiency of this lesson.

Write down 2 things you want to know more about.

Here, students enter two things they would like to know more about. This not only increases involvement, but also gives them more ownership.

Ask 1 question about something you haven't quite understood yet.

The students indicate here (in question form) with which part of the material they still have difficulty. For the teacher, this not only provides insight into the extent to which the students understand/master the material, but also a good starting point for the next lesson.