Timber 5

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Level 2 Diploma in Painting and Decorating

PowerPoint Timber

Unit 215: Preparing surfaces for decoration

Learning outcomes •  Know how to prepare timbers and timber sheet products ready to

receive finishing systems.

•  Be able to prepare timbers and timber sheet products ready to receive finishing systems.

Timber classification

Timbers are identified as softwood and hardwood, according to their characteristics.

In groups identify two softwood and hardwood trees.

Softwood Hardwood Faster growing Slow growing

Evergreen Deciduous

Needles instead of leaves Broad leaves

Shorter roots Longer roots

Hardwood and softwood trees Softwood Hardwood

Softwoods

•  Evergreens are easier to cut than hardwood trees, which are denser.

•  However, there is no minimum weight requirement to become a hardwood (eg balsa wood).

Types of trees •  Conifer •  Fir •  Cedar •  Pine Uses Door frames, architraves and frames, low budget furniture, stud partitions etc.

Hardwoods

•  Most are deciduous (their leaves are large, broad and fall off each autumn, growing back again in the spring).

•  Not always harder than softwood.

Types of trees

•  Oak

•  Elm

•  Beech

•  Mahogany

Furniture making, floors and exterior doors (usually varnished, oiled or stained).

Properties of timber Task

In groups describe the following properties of timber:

•  Porosity

•  Adhesion

•  Capillaries

Moisture content Task

Discuss in groups what moisture is and how it can affect timber.

•  Wood can hold large amounts of water because it is made up of cells.

•  Seasoned timber should contain no excess moisture.

•  Seasoned timber should not be exposed to any contact with water or moisture prior to any protective coating being applied.

•  Heavy moisture can cause fungi or dry rot, reducing the weight and strength of the wood.

Moisture content

Recommended amount of moisture in timber prior to painting

Not exceeding 21%

Process of the removal of moisture in timbers

Seasoning (by air or kiln)

•  To check the amount of water, use an instrument called a moisture meter.

Timber sheets/boards Timber is a sustainable material that can be recycled from its original source.

By re-manufacturing we can benefit from other properties such as:

•  Improved strength

•  Smooth surfaces

•  A new waterproof product

•  Increased ease of cutting

Timber sheets/boards There are a variety of different timber boards, all with different uses and advantages.

•  Plywood

•  Oriental strand board (OSB)

•  Medium density fibre board (MDF)

•  Chipboard

•  Blockboard

•  Hardboard

In groups describe the types of board (Activity 9).

Timber is a natural organism, prone to defects.

Knots – most common defect: result of the branch in the tree.

•  The knot may be live, sound, or tight. •  Dead knots become loose and downgrade

the appearance and stability of the board •  The more knots, the lower the quality of

the wood. Task

Knots require sealing prior to painting.

What would be the recommended coating for the defect: shellac knotting or aluminium wood primer?

Timber defects

Timber defects End grain

Trees are felled and the timber is cut into planks leaving the end grain exposed – the most absorbent part of the timber.

What is the recommended treatment for end timber?

•  Preservative, shellac, aluminium wood primer and oily primer.

Timber defects Splits and cracks

Ruptures or separations in the grain of the wood which reduce quality as measured by appearance, strength or utility.

May be caused by:

•  Excessive moisture

•  Extreme machining

•  Mechanical damage

•  Growth stresses

Questions

1. Identify one softwood and one hardwood timber and state their uses in construction.

2. What is the recommended amount of moisture content for timbers?

3. What is the term ascetics?

4. What method is used to remove moisture in timber?

Any questions?

Timber 5

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