Introduction to Natural and Manufactured Timber

Welcome! In this chapter, we are exploring one of the most versatile and oldest building materials in the world: timber. Whether it's the chair you're sitting on or the desk you're working at, timber is everywhere. We will look at the three main types: Hardwoods, Softwoods, and Manufactured Boards. By the end of these notes, you'll understand why a designer might choose a piece of solid Oak for a luxury table but use MDF for a kitchen cabinet.

1. Natural Timbers: Hardwoods vs. Softwoods

Natural timber comes directly from trees. Even though the names "hardwood" and "softwood" suggest how tough the wood is, the names actually describe how the tree reproduces and grows.

Hardwoods

Hardwoods come from deciduous trees. These are trees that usually have broad leaves and lose them in the autumn. They grow slowly, which usually makes the wood denser and more expensive.

  • Oak: Very strong, heavy, and durable. It has an attractive grain and is used for high-quality furniture and flooring.
  • Birch: Has a fine, uniform texture. It is quite hard and often used for furniture or as the outer layers of plywood.
  • Teak: Contains natural oils that make it highly resistant to moisture and decay. This makes it perfect for outdoor furniture and boat decks.

Softwoods

Softwoods come from coniferous trees. These trees have needles instead of leaves, stay green all year round (evergreens), and produce cones. They grow much faster than hardwoods, making them cheaper and more sustainable.

  • Pine: A very popular "all-rounder." It is easy to work with, relatively cheap, but can have lots of knots. Used for internal building work and simple furniture.
  • Cedar: Very lightweight and naturally resistant to rot and insects. Because it survives well outside, it is often used for "cladding" (the outside skin of buildings) and sheds.
  • Spruce: Has a high strength-to-weight ratio. It is often used for structural work in houses (like roof rafters) and even musical instruments.

Quick Review: Don't let the names fool you! Some softwoods can be quite hard, and some hardwoods (like balsa) are very soft. The real difference is the type of tree they come from.

2. Manufactured Boards

Manufactured boards are "man-made." They are created by taking waste wood (like sawdust, shavings, or thin layers) and gluing them together under pressure. Designers love them because they come in huge, flat sheets that don't warp or twist like natural wood can.

  • MDF (Medium Density Fibreboard): Made from tiny wood fibres glued together. It is very smooth and easy to paint, but it's heavy and can soak up water like a sponge if not sealed.
  • Plywood: Made by gluing thin layers (veneers) of wood together. The "grain" of each layer is turned \(90^{\circ}\) to the one below it. This makes it incredibly strong and stable.
  • Block board: Features a core of solid wood strips sandwiched between two layers of veneer. It is very rigid and great for long shelves that shouldn't sag.

3. Properties of Timber

When selecting a material, designers look at its characteristic properties. Here are the key terms you need to know:

  • Density: How "compact" the wood is. \(Density = \frac{mass}{volume}\). Denser woods like Oak feel heavier.
  • Strength: The ability to withstand a force without breaking.
  • Hardness: How well the surface resists scratches and dents.
  • Durability: How well the wood lasts over time, especially when exposed to weather.
  • Absorbency: How much moisture the wood takes in. High absorbency can lead to rotting.

4. Sources, Origins, and the Environment

Timber is a renewable resource, but only if we manage forests properly. Harvesting involves cutting down trees, which are then converted into usable planks at a sawmill.

The Lifecycle & Ethics:
Working with timber has an ecological impact. Transporting heavy timber across the world uses fossil fuels and creates \(CO_{2}\). To be ethical, many designers look for the FSC (Forest Stewardship Council) logo, which proves the wood came from a forest where new trees are planted to replace the ones cut down.

Recycling and Reuse: Timber can be upcycled (turning an old pallet into a coffee table) or recycled by chipping it down to make manufactured boards like chipboard.

5. Stock Forms and Calculations

Timber isn't sold by the "tree"; it is sold in stock forms. This makes it easier for designers to plan their projects and calculate costs.

  • Standard Forms: Planks (flat boards), Rods/Dowels (circular sticks), and Sheets (usually \(2440mm \times 1220mm\) for manufactured boards).
  • Maths Tip: To calculate how much material you need, you often need the Surface Area.
    For a rectangular board: \(Area = length \times width\).
    If a board is \(2m\) long and \(0.5m\) wide, the area is \(2 \times 0.5 = 1m^{2}\).

6. Manufacturing Processes

In the workshop, you will use three main "families" of processes to turn timber into a product:

Wastage (Cutting away)

This is when you remove material to get the shape you want.
Examples: Sawing with a tenon saw, drilling holes, or using a Chisel to carve wood. CNC Routers can also be used to cut complex shapes automatically.

Addition (Joining)

This is putting pieces together.
Examples: Using wood glue (PVA), screwing pieces together, or using traditional joints like a butt joint or dovetail joint.

Deforming and Reforming (Changing shape)

This is changing the shape of the wood without cutting it.
Example: Steam Bending. If you soak wood in steam, it becomes flexible. You can then bend it into a curve, and when it dries, it stays in that shape!

7. Finishing Timber

Raw wood can be rough, absorbent, and easily damaged. We apply finishes for two reasons: Function (to protect it) and Aesthetics (to make it look good).

  • Varnish: Creates a hard, clear waterproof skin.
  • Paint: Covers the grain and adds colour.
  • Oil/Wax: Soaks into the wood to bring out the natural grain and provide a light layer of protection.
  • Preservatives: Used on outdoor wood (like fences) to stop insects and rot from eating the timber.

Key Takeaways for the Exam

1. Know your examples: Oak/Teak/Birch (Hardwood), Pine/Cedar/Spruce (Softwood), MDF/Plywood (Manufactured).
2. Remember that manufactured boards are stable and come in large sheets, while natural woods have beautiful grains but can warp.
3. Always consider the environment—look for sustainable sources and think about the "miles" the wood has travelled.
4. Be ready to calculate the area or cost of timber using simple multiplication: \(Total Cost = Quantity \times Price\).