Timber

timber and its market form

1. timber

2. Contents… Introduction Advantages Uses of timber Market forms of timber Veneers Plywood

3. INTRODUCTION

4. Timber is another name for wood, whether still standing in the form of trees or felled and turned into boards for construction. Timber is very common for engineering purposes as it is considered as an important structural material. There is a difference between wood and timber . Wood includes all types of wood which maybe burning wood, structural wood, furniture wood etc. But wood suitable for use as a structural material is called Timber .

5. ADVANTAGES It is easily available every where. Its salvage value is high. It can be easily transported by converting large pieces into smaller pieces. It can be easily joined. Being light in weight it is preferred for building works in earthquake prone areas.

6. Uses of timber It is very much used for railway track sleepers. It can be used as members of roofing trusses. It is an important material for furniture making. It is used as form work for cement concrete structures. Packing cases are mostly made from soft timber. It is used for floors, ceiling ,partition walls. Etc.

7. Timber used as frame work Timber used for making furnitures . For packaging Timber is used for railway sleepers

8. Defects in timber… The defects that usually occur in the timber may be classified into two categories: Defects that develop during growth of the tree. Defects that develop after felling the tree.

9. Some of the Defects that develop during growth of the tree…

10. Some of the Defects that develop after felling the trees… SPLIT

11. Preservation of timber… The methods that are commonly used for the preservation of timber are: 1.charring 2.tarring 3.painting 4.creosoting 5.wolman’s salt 6.ascu-treatment 7.vaccum-pressure process 8.hot and cold process 9.seasoning of the timber.

12. Qualities of good timber Following are the qualities of good timber- A good timber should be hard and durable. It should be capable of resisting the actions of fungi, chemicals and physical agencies. The fibers of the timber should be straight and compact. Its freshly cut surface should smell sweet. Its weight should be heavy. Timber should be tough i.e. should be capable of resisting shocks. It should be able to withstand the weathering effects. A clear ringing sound should be emitted by the timber when struck. Heavy dull sound indicates decayed timber. It should offer adequate fire resistance and should be elastic.

13. Market forms of timber Battens : these are small sectioned timber pieces. No cross sectional dimension exceeds 5 cm in battens. Logs : trunk of trees left after removing all the branches is known as log. Baulk : it is roughly squared swan log .one of the cross sectional dimensions exceeds 5 cm while the other exceeds 20 cm. Planks : it is a timber piece with parallel sides. Its thickness is always less than 5 cm and width always more than 5 cm.

14. Board : it is a timber piece with parallel sides whose thickness is always less than 5cm and width always more than 15cm. Deal : it is again a parallel sided piece whose thickness varies from 5cm to 10cm and width does not exceed 23cm. Scantlings : these are timber pieces whose breadth and thickness are always more than 5cm but their length is always than 20 cm. Pole : it is a log having its diameter not more than 20cm. It is also known as spar .

15. veneers

16. Veneers are thin sheets of timber of very superior quality. they are obtained by rotating wooden logs of very high quality timber against a sharp knife of rotary cutter. Thickness of veneer may vary from 0.4mm to as much as 6mm or even more. It is peeled off from timbers like teak, rosewood, oak, mahogany etc. The process of preparing a sheet of veneers is known as veneering. It may also include gluing of veneer sheets of superior quality over a base of wood of inferior quality.

17. plywood

18. Ply means thin layer. Plywood is in form of boards prepared from thin layers of wood or veneers. Veneers in plywood are taken in odd numbers and are then placed one above the other with the direction of grains of successive layers at right angles to each other. All veneers are held together by adhesives. The direction of grains at right angles in successive veneers increase the strength of the plywood. The face of the plywood with better finishing is known as face and other exposed face as back of the plywood. Plywood sheets are manufactured in size varying from 90cm*90cm to 240*120cm.

19. Advantages… They suffer little expansion or shrinkage due to variation in moisture content. They are light and are available in large sizes. They are available in decorative designs. They are not liable to split or crack. They make use of costly timbers in most economical manner. They re easy to work with.

20. Difference b/w vener and plywood Plywood is a type of  manufactured wood  panel. It is made by gluing together plywood layers, also called veneers. These veneers are glued together with adjacent plies having their wood grain at right angles to each other. Veneer, on the other hand, refers to thin slices of wood that are practically peeled of the wood. The slices are usually less than 3 mm (1/8 inch) thick.  

21. Fiber boards

22. Fiber boards are manufactured from wood or other vegetable fiber. The pieces of wood, cane, or other vegetable fibers are heated in a hot water boiler. Due to boiling wood fibers get separated. These fibers are put in a vessel and steam is admitted in it under pressure. The steam pressure is then suddenly increased which is then maintained for few seconds. In doing so the natural adhesive contained in fibers is separated completely.

23. The fibers are then taken out of vessel and cleaned of all superfluous gums. the fibers also obtained are spread on wire screen I forum of loose sheets and pressed. The resulting material is called the fiber board. These are rigid boards of thickness varying from 6mm to as much as 25mm. Their width is 1.2m and length 3.5m. They are also known as presses wood or reconstructed wood.

24. Depending upon their form and composition fiber boards are classified as insulating boards, medium hard boards, super hard boards, hard boards and laminated boards. Uses : 1. For the construction of wall panels and suspended ceilings. 2. To construct partitions. 3. As insulting material against heat and sound. 4. As table tops and for flush doors.

25. Hardwood and soft wood Hardwood contrasts with softwoods Hardwoods are not necessarily harder than softwoods. In both groups there is an enormous variation in actual wood hardness, with the range in density in hardwoods completely including that of softwoods; some hardwoods ( e.g. ,  balsa ) are softer than most softwoods, while  yew  is an example of a hard  softwood .

26. Impreg timber

27. Laminates, formica, sungloss etc are the examples of impreg timber. Impreg timber is nothing but timber fully or partly covered with resin. Impreg timbers are strong, durable, good looking and are not affected by moisture and weather conditions. They resist acidic effects and are electrically insulated.

28. Properties of some important timber

29. babul Its timber is strong, hard and tough. It is durable but difficult to work. Its texture is quite strong. It is not available in large lengths. Its color is whitish red which turns to red brown due to exposure. It is used for the construction of bullock carts, tool handles, well curbs and agricultural implements etc. Bullock cart Logs of babul tree Wooden handle

30. deodar It is compact, hard, durable and strong. It is yellow in color. It is easy to work with. Receives varnish very easily. It is used for railway sleepers, piles and other construction work, cheap furniture and railway carriages.

31. sal Its color is either light brown or yellow. It is hard, compact and heavy. It is durable and strong. It cannot be finely polished. Its seasoning is very slow. It cannot be used for decorative purpose because its surface cannot be finely finished. It is mostly used for tent pegs, doors and window frames etc.

32. teak It is used for ship building, railway sleepers, furniture, railway carriages. It can be used for any structural or decorative purpose. It is a costly timber and hence used for costly and specialized work. It can be easily seasoned and is easy to work with. It does not wrap due to shrinkage and is fire resistant, acidic action resistant and also white ant resistant.

33. shisham It is used for furniture, ply wood, sports goods, railway sleepers etc. It is dark brown in color with golden and dark brown colored lining. It can be easily seasoned and receives high class polish. It is difficult to work with.

34. Aini : it is yellowish brown and can be used under water. It takes fine polish. Arjun : it is dark brown and is heavy timber.used for rafters, beams etc Bamboo : used for scaffolding, thatch roofs etc. Mahogany : used for furniture, pattern making, cabinet work etc. it is reddish brown in colour . It contains resinous oil to save itself from insect attack. Mulberry : it is tough, elastic and strong. It takes clean finish and is used for baskets, hockey sticks, sports and furniture.

35. Cambium layer The bark on the outside of the tree protects the Living cambium layer that lies just underneath. It is the cambium layer that produces the growth rings inside the tree, adding new layers of phloem and xylem each season .

36. Difference b/w m.d.f and h.d.f MDF HDF MDF is a product of soft woods that are broken down by a defibrator, added to wax and resin, and formed from heat and pressure. MDF is sensitive to moisture. HDF is also a product of soft woods that are broken down by a defibrator, added to wax and resin and formed from heat and pressure. But it is much more dense and made from exploded wood fibres. HDF is highly resistant to mold and infestation and is not sensitive to moisture.

37. Endogenous and exogenous Exogenous trees  grow in width by forming a new layer of wood under the bark. Endogenous trees grow by forming new fibres within the trunk interspersed with the old fibres.

38. bibliography Building materials by Gurucharan Singh. www.google.com www.slideshare.net

39. Thank you