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Conceptual Understanding: Timber is a major building material that is renewable and uses the Sun’s energy to renew itself in a continuous cycle. While timber manufacture uses less energy and results in less air and water pollution than steel or concrete, consideration needs to be given to deforestation and the potential negative environmental impact the use of timber can have on communities and wildlife.
Characteristics of natural timber: Natural timber is timber that is used directly from the tree after being seasoned (a controlled drying process).
The tensile strength of timber is greater along the grain (fibre) than across the grain (matrix).
Natural timber is classified into two main categories: Softwood and Hardwood.
Temperate forests are in the regions between the tropics and the polar areas, mainly in the northern hemisphere. Both hardwoods and softwoods grow in temperate forests. Tropical forests are in the region between the 2 tropics. Generally only hardwoods are found in these forests.
Hardwood: The wood from a deciduous (broadleaved) tree.
hardwood trees also bear fruit, such as nuts, seeds or acorns
They can take up to 100 years to mature making them rarer and more expensive
hardwoods timber has comparable mechanical properties of strength, hardness and durability
hardwood is mostly of a higher density and hardness than a softwood.
aesthetics of hardwoods is usually very appealing which makes it very desirable and often used in high-quality furniture
hardwoods contain much more fibrous material than softwoods. The fibers are smaller and more compact, making it stronger and harder
in general, the greater the density of wood, the greater its mechanical strength
Beech - A straight-grained hardwood with a fine texture. Light in colour. Very hard so is ideal to be used where it is being bashed around and used often. Beech is also very easy to work with.
Used for furniture, children’s toys, tool handles. Can be steam bent and laminates well.
Teak - A very durable oily wood which is golden brown in colour. Highly resistant to moisture as it contains natural oils.
A very durable oily wood which is golden brown in colour. Highly resistant to moisture and outdoor weather
Oak - A very strong wood which is light in colour. Open grain. Hard to work with. When treated it looks very classy and elegant.
A very strong wood which is light in colour. Open grain. Hard to work with. When treated it looks very classy and elegant.
Softwood: The wood from a coniferous (evergreen) tree.
coniferous trees which are evergreen, needle-leaved, cone-bearing trees, such as cedar, fir and pine
aesthetics: Softwoods are generally a pale yellow with brown streaks. Pine is very resinous and at times this resin can leak out of the timber. Resin is really sticky and messy and will also come through painted surfaces
many softwoods will change color if exposed to sunlight for long periods of time
softwoods are also prone to decaying and warping, bowing, cupping and splitting much quicker than hardwoods
softwoods are usually made up of tube-like cells (similar to holding up a bunch of straws together). This would make the softwoods less dense and more prone to water damage. The timber absorbs water just like a sponge if the end grain is exposed.
Scots pine - A straight-grained softwood but knotty. Light in colour. Fairly strong but easy to work with.
Used for DIY and cheap quality furniture. Mainly used for constructional work and simple joinery.
Spruce - Creamy-white softwood with small hard knots. Not very durable.
Used for general indoor work, whitewood furniture used in bedrooms and kitchens.
European redwood - Quite strong, Lots of knots, durable when preserved.
Used for general woodwork, cupboards, shelves, roofs.
The world’s forests can be divided into temperate and tropical.
Temperate forests are in the regions between the tropics and the polar areas, mainly in the northern hemisphere. Both hardwoods and softwoods grow in temperate forests. Tropical forests are in the region between the 2 tropics. Generally only hardwoods are found in these forests.
Seasoning:
Timber is seasoned as part of its preparation for commercial use. This process reduces the moisture content so that it becomes workable. The remaining moisture, albeit small, means that the wood never really stabilises and continues to swell and shrink, with humidity and temperature variations.
1) Air Seasoning
Advantages: No expensive equipment needed, Small labour cost once stack is made, Environmentally friendly-uses little energy.
Disadvantages:Takes longer than Kiln seasoning, large area of space required for a lot of wood, it is notable to produce timber not dry enough for use in the dry, centrally heated air of modern buildings due to the relative humidity in the atmosphere at location of drying site.
2) Kiln Seasoning
Advantages: Insects are killed during this process, Require little stacking space, Moisture content of the timber may be brought to any desired level, It is dries quickly, It can be controlled, Achieve a lower moisture content, Defects associated with drying can be controlled.
Disadvantage: It is expensive , It gives a little weaker timber when compared to air seasoning, requires supervision by a skilled operator, uses a lot of energy.
Faults with natural timber
Natural woods are also subject to movements such as splitting, cupping, warping and bowing. All of these would make the wood unusable.
This is why seasoning timber is vital.
Knots will make the timber weaker, but it can be used from an aesthetic point of view.
Characteristics of man-made timbers: Also known as engineered wood or composite wood, these are wood products that are made by binding or fixing strands, particles of fibres, veneers of boards of wood together with adhesives or other fixing methods to create composite materials. Typical examples include MDF, plywood and chipboard.
Characteristics include tensile strength, resistance to damp environments, longevity, aesthetic properties.
Advantages
available in large flat sheets- 2440 x 1220mm so can be used for large pieces of furniture without having to join pieces.
good dimensional stability- they don’t warp as much as natural timber.
can be decorated in a number of ways, eg, with veneers or paint.
sheets of plywood and MDF are flexible and easy to bend over formers for laminating.
waste from wood production can be used to make MDF, chipboard and hardboard.
Disadvantages
sharp tools required when cutting manufactured boards, and tools and easily blunted.
difficult to join in comparison with traditional construction methods- you cannot cut traditional woodwork construction joints such as finger or dovetail joints.
thin sheets do not stay flat and will bow unless supported
cutting and sanding some types of board generates hazardous dust particles.
edges must be treated and covered to hide unsightly edges and to stop water getting in, a process called concealing edges; this also helps to create a better appearance of a solid piece of timber.
Characteristics of Laminate man-made timbers: Laminate Board such as Plywood is a material manufactured from thin layers or "plies" of wood veneer that are glued together with adjacent layers having their wood grain rotated up to 90 degrees to one another.
Can be decorated with a plastic or wood veneer to make it appear more expensive, give a harder scratch resistant work surface.
Characteristics of Particle Board man-made timbers: Particle Board is an engineered wood product manufactured from wood chips and a synthetic resin or other suitable binder, which is pressed and extruded.
Can be decorated with a plastic or wood veneer to make it appear more expensive, give a harder scratch resistant work surface.
Treating and finishing timbers: These are an additive preservative to improve the timber's resistance to attack and improve its durability is enhanced to a level which is suitable for the intended use. Timber treatments & finishes are used to protect, enhance and improve the mechanical properties.
Timber finishes- are applied to the surface of the timber and is usually carried out to achieve one or both of the the following reasons:
Aesthetics- to improve the materials natural beauty
Function- to protect it from environmental impact, heat, moisture, resistance to attack from insects, termites or fungi
Finished timber requires sanding with abrasive paper to close up the grain leaving smaller gaps.
eg. varnish/estapol, finishing oil, wood wax, wood preserver, creosote, stain preservers
Recovery and disposal of timbers: Timber is one of the most renewable and 'earth friendly' materials available which makes the principle and practical aspect of recovery and recycling quite straight forward.
1. Reforestation is the process of restoring tree cover to areas where woodlands or forest once existed. If this area never returns to its original state of vegetative cover the destructive process is called deforestation. In order to maintain a sustainable forest industry reforestation is necessary.
2. Wood recycling is the process of turning waste timber into usable products. Recycling timber is a practice that was popularized in the early 1990s as issues such as deforestation and climate change prompted both timber suppliers and consumers to turn to a more sustainable timber source. Recycling timber is the environmentally friendliest form of timber production and is very common in countries such as the UK, Australia and New Zealand where supplies of old wooden structures are plentiful. Timber can be chipped down into wood chips which can be used to power homes or power plants.
3. Uses for recycled waste wood include traditional feedstock for the panel board industry, which still accounts for the majority of recycled wood. Other uses include animal beddings, equestrian and landscaping surfaces, play areas and filter beds.
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