Timbers Flashcards
(44 cards)
Features of soft woods
- They grow in cooler climates
- Come from Coniferous trees
- They have a looser grain structure
- They are often used as a building material
- These are usually softer and easy to work with (due to having a looser grain)
- As the trees grow tall and straight, the manufacturer can cut it into long straight planks of wood.
- They grow quite faster and are cheaper
- They do not lose their needles.
Hardwoods
- Come from deciduous trees (lose their leaves in the winter)
- Tend to have a tighter grain so they are usually quite hard
- They can be very expensive
- They take 100 years to fully grow
Manufactured Boards features
- Made in many thicknesses
- Inexpensive so are often used instead of real woods
- Manufactured boards are often covered with a thin layer of real wood called a veneer to improve appearance or properties
- THESE ARE timber sheets which are produced by gluing wood layers or wood fibres together
- Made usually from waste wood
- They have been developed mainly for industrial production as they can be made in very large sheets of consistent quality.
Name the softwoords
Pine, Spruce, Douglas fir, Redwood, Cedar, Larch
Name the hardwoods
- Oak
- Ash
- Mahogany
- Teak
- Birch
- Beech
Man-made timbers
- Plywood
- Marine plywood
- Aeroply
- Flexible plywood
- Chipboard
- Medium density - fibreboard (MDF)
What are the stock forms of timber?
- Rough sawn
- Planed Sqaure Edge (PSE)
- Planed all round (PAR)
- Natural timber
- Manufacture board
- Mouldings
What does rough sawn mean?
The wood comes directly from seasoning and has rough surfaces produced from initial conversion. Rough sawn wood will have nominal sizes rather than accurate finished size.
What is PSE?
Planed square edge 9PSE0 wood has only one edge that is planed accurately; the rest are rough sawn. Planing removes about 3mm from the original normal size.
What is Planed all Round?
PAR wood has sides and edges that are all planed square, straight and level, leaving a smooth finish, and is ready to use. The PAR board is about 3mm smaller all round than the original rough sawn nominal size.
What are mouldings?
Some wood is made into mouldings such as skirting boards or wooden trims and are readily available in standard lengths up to approximately 4 metres.
What are veneers?
Thin slices of wood less than 3mm thick.
What happens when wood rots or burned?
Greenhouse gases are released, contributing to climate change.
Why are trees important?
They act as carbon ‘sinks’ that absorb the gases.
What does using a recycled timber product mean?
Using a recycled timber product reduces deforestation and retains the locked-in carbon.
What are the two types of seasoning on timbers?
- Natural seasoning
- Kiln seasoning
What is the method of natural seasoning?
It is an inexpensive method which involves stacking the wood under a shelter, protected from the rain. Air circulates between the planks to slowly remove the excess moisture. Air-seasoned wood is used for outdoor wooden products because it is seasoned to the same moisture content as its surroundings and therefore the wood will be less prone to defects.
What is kiln seasoning?
- Planks are stacked onto trolleys and placed in the kiln where both temperature and humidity are controlled. Initially, the kiln atmosphere is very steamy but this is gradually changed to become hotter and drier. Indoor products such as furniture will use kiln-seasoned wood because it has been seasoned to meet indoor conditions and will have a lower moisture content than air-dried wood.
Natural seasoning advantages
- Cheap
- Some say the timber is stronger than kiln seasoned
Natural seasoning disadvantages
- Every flow (a year per inch thickness
- Bugs and fungus survive
- Water content hard to control accurately
- Ends of planks can split
Kiln seasoning advantages
- Accurate water content achieved
- 12% or lower moisture
- Kills bugs and fungus
- Faster than natural seasoning
Disadvantages of kiln seasoning
- Expensive
What are some timber defects?
Splitting
Knots
Timber decay - Dry rot
Woodworm
What is splitting?
- Usually occurs at the end of a plank
- Ends are cut off to remove splits
- Generally an unavoidable problem
- Painting the ends of planks can help slow down the drying of the ends