6-performance and characteristics of woods

• Rough sawn


  Wood that comes direct from seasoning and has rough surfaces produced from initial conversion; rough-sawn wood will have nominal sizes rather than accurate finished sizes
• Planed square edge (PSE)


  Wood has only one edge that is planed accurately, the rest are rough sawn (about 3 mm smaller in width from the original nominal size)
• Planed all round (PAR)


  Wood has sides and edges that are planed square, straight and level, leaving a smooth finish, and is ready to use (about 3 mm smaller all round than the original rough-sawn nominal size)
• Manufactured board


  Man-made and produced in large sheets, typically 1220 mm x 2440 mm
• Wood is a natural material, which will naturally biodegrade if left in landfill
• Wood


  • Wood fibres grow along the length of the tree or branch (grain) and these fibres consist of hollow cells (tracheids) supported by lignin resin
  • Wood expands and shrinks with changes in humidity
  • Wood is strong in the direction of the grain (along the grain) and weaker across the grain
• Seasoning wood


  1. Converted from the tree it is sawn into useable pieces

  2. Seasoned (air or kiln) to remove the excess moisture, 80-90 per cent, before use

  3. Seasoned to help prevent defects such as twisting, warping, cracks, cupping or bowing

  4. To reduce the time taken to season wood, trees should be felled in the winter when they grow less, have less sap and therefore contain the least moisture
• Air seasoning


  Traditional and inexpensive method of seasoning that involves stacking the wood under a shelter, protected from the rain, air circulates between the planks to slowly remove the excess moisture
• Kiln seasoning


  More expensive but controlled method that is very quick and can take just a few weeks, planks are stacked on to trolleys and placed in the kiln where both temperature and humidity are controlled
• Hardwood


  A wood from a broad-leaved (deciduous) tree
• Softwood


  A wood from a cone-bearing (coniferous) tree
• Classification of woods


  • Hardwoods: Oak, Ash, Mahogany, Teak, Birch, Beech
  • Softwoods: Pine (European redwood), Spruce, Douglas fir, Larch, Cedar
• oak

  • Hard, tough, attractive grain, good weather resistance, contains tannic acid which will corrode steel screws or fixings, uses:furniture,flooring,boat building
• pine

  • Straight grain, knotty, can contain resinous knots, uses: construction work, roof beams
• Manufactured boards


  • Plywood
  • Veneers
  • MF Laminates
  • Marine plywood
  • Aeroply
  • Flexible plywood
  • Chipboard
  • MDF
• Plywood


  • Thin layers of wood are placed and glued at 90 degrees to one another and compressed to form the board, good strength in all directions, no grain weakness, always has an odd number of layers, uses: desktops, indoor furniture, floorboards
• Marine plywood


  • Similar construction to plywood but is gap and void free, and uses specialist water and boil-proof (WBP) glue to provide resistance to moisture, some higher-quality marine plywood is also resistant to fungal attack, uses: boat dashbaords, boat locker and panelling
• Aeroply


  • Plywood made from high-quality timber such as birch, available in very thin sheets, lightweight, easy to bend around a support frame, uses: laser-cut project, jewellery projects
• Flexible plywood


  • An odd number of layers glued together with the two outer layers made from open-grained timber, which allows the sheet to flex, bent and glued around a former to achieve a solid shape, uses: laminated furniture, curved panels
• Chipboard


  • Wood chips compressed with a resin such as urea formaldehyde, uses:shelving, kitchen worktops
• MDF


  • Compressed wood fibres, sometimes urea formaldehyde is added as an additional resin, has two smooth faces, available in either standard grade or veneered with a layer of timber, uses:model, furniture eg bookcase, desks, cabnets
• Veneers


  Thin slices of wood less than 3 mm thick, uses; decorative coverings for manufactured boards
• MF Laminates


  Thin sheets of MF polymer, hard, tough, chemical resistant, uses: decoraive covering for chipboard for kitchen worktops
• The toxicity of a wood depends on the species, and both wood dust and sap can be a hazard
• Different species have different risks (can cause respiratory irritation and hardwood dusts are listed as carcinogenic) and under the Control of Substances Hazardous to Health (COSHH) regulations 2002, both hardwood and softwood dusts have workplace exposure limits (WEL) of 5 mg per cubic metre
• Employers should provide personal protective equipment (PPE) and make sure extraction and ventilation systems are used so as not to exceed the WEL
• douglas fir


  straight or slightly wavy grain, few knots, stable, good resistance to corrosion, uses: veneers, plywood construction, consruction work
• cedar


  straight grain, can corrode ferrous metals due to acidic nature low density, good sound damping and insect resistant, uses: sheds, greenhouses, beehives, interior panelling
• spruce


  straight grain, resistant to splitting, uses: indoor furniture
• larch


  hard, tough, attractive grain pattern fades to silver upon exposure outside, uses: garden furniture, cladding, decking, fencing
• ash


  tough, attractive open grain pattern, which makes it more flexible, uses: tool handels, ladders, sports goods, laminating
• mahnogany


  rich, dark red colour, can contain interlocking grain making it more difficult to work. uses: indoor furniture, shop fittings and cabinets
• teak


  hard, tough, straight grain, natural oils resisit moisture, acids and alkalis, uses: outdoor furniture, boat decks
• birch


  hard, straight close grained, resists warping, uses: furniture, indoor panelling
• beech


  tough, close grained, hard, avalible in steamed(white) and unsteamed (pink), uses:chairs, chopping boards