1. PALESTINE UNIVERSITY
BUILDING MATERIAL
Chapter No. 4
Timber

2. Carpentry General
Timber has been in very common use for- engineering purposes since ancient times. Even to-day there are certain works, where timber is considered as the most ideal material. To-day although materials like steel, cement, stone bricks etc. have occupied lot of field, where timber was predominantly used, still timber continues to be an important structural material.
There is difference between terms timber and wood. Wood includes all types of wood which may be burning wood, structural wood, furniture wood etc. But wood suitable for use as a structural material is called timber.

3. Carpentry General
Timber is obtained from trees. Timber denotes structural wood. A standing living tree is known as standing timber.
Rough timber.
When tree has been cut and its stem and branches are roughly converted into pieces of suitable lengths.
Converted timber
When roughly converted timber is further sawn and converted into commercial size the planks, logs, battens, posts, beams, etc

5. Carpentry Advantages of Timber
It is easily available every where.
Its salvage value is high.
It can be easily transported by converting large pieces into smaller pieces.
Working on timber is easy. Timber constructions can be easily repaired. Additions and alterations to timber structures can be easily done.
It can be easily jointed.
In marine works, timber is considered as an ideal material as it does not corrode. Cement and iron structures corrode in sea water, if they are not protected with special preservative.

6. Carpentry Advantages of Timber
Being light in weight, it is preferred for building works in earth quake prone regions.
It is an excellent material for decorative and general use furniture. Lot of other internal decorations can be carried out with it.
It can with stand, shocks better than iron and concrete.
It is good insulator of electricity and heat.
It is good sound absorbing material.
Timber can be easily strengthened by attaching steel or other material with it.

7. Carpentry Use of Timber
It can be said that there is no Engineering field, where timber is not used one way or the other.
Uses of timber are numerous. Some of its important uses are given as follows:
It is very much used for railway track sleepers.
It can be used inform of piles, vertical posts, beams, lintels, doors and windows.
It can also be used as members of roofing trusses.
It is an important material for furniture-making
It is used for floors, ceiling, and partition walls.

8. Carpentry Use of Timber
It is used as form-work for cement concrete structures.
It is very much used in making sports. goods, musical instruments, well curbs, agricultural implements, etc.
Packing cases are mostly made from soft timber.
It is very much used for timbering the deep. trenches.
Railway coaches and wagons are also made from high class timber.

11. Carpentry 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.
The timber should be free from knots, twists, upsets, burls shakes, flaws etc.
Its colour should be dark. It should be obtained preferably from heart wood. Colour should be uniform.
It should be properly seasoned.
Its freshly cut surface should smell sweet.

12. Carpentry Qualities of Good Timber
Its weight should be heavy.
It should be easily workable. It should not clog the teeth of saw and should be capable of being easily planned.
Timber should be tough i.e., it should be capable of resisting shocks.
It should be able to withstand the weathering affects.
It should be strong enough to withstand bending, direct and shear effects efficiently.
A clear ringing sound should be emitted by the timber when struck. Heavy dull sound indicates decayed timber.
It should offer adequate fire resistance.
It should be elastic

13. Carpentry Defects in Timber
The defects that usually occur in the timber may be classified into two categories as follows:
Defects that develop during growth of the tree.
Defects that develop after felling the tree.

14. Carpentry Defects in Timber
Defects that develop during growth of tree have been briefly discussed as follows:
Shakes. This is most serious type of defect in timber. These are sort of cracks which partly or completely separate the fibers of wood. A shake is nothing, but separation of the timber along the grains. Shakes may be of several types.

15. Carpentry Defects in Timber
Star shakes.
These are radial cracks or splits that extend from bark towards the sap wood. They usually remain confined up to the plane of sap wood only. The cracks are widest at the circumference and go on narrowing as they proceed towards the Centre of the tree. Star shakes usually develop due to fierce heat and frost When logs having this defect are sawn they usually separate out into a number of pieces and hence become useless.

16. Carpentry Defects in Timber
Heart shakes.
These splits or cracks occur in the central part of the trees. There are widest at the centre and go on narrowing as they proceed towards outside. This defect usually occurs in over-matured trees. This defect is usually caused due to shrinkage of the heart wood. Heart shakes divide the tree cross-section into several parts. Straight running heart shake is not as serious as twisted heart shake.

17. Carpentry Defects in Timber
Cup shakes.
This defect develops curved slit between successive annual rings. The split does not run for the full circumference of the annual rings. This defect usually develops due to unequal growth. Another possible reason for their development may be contraction of timber under atmospheric changes together with the twisting action of strong winds.

18. Carpentry Defects in Timber
Ring shakes.
When cup shake defect runs for full circumference of the annual ring, it is called ring shake. It is more serious than cup shake.
Radial shakes.
They are similar to star shakes. They are numerous, fine and irregular. They usually occur when felled tree is exposed to sun for seasoning. The cracks run for a short distance from bark to-wards the centre and then follows the course of an annual ring and ultimately goes towards the pith.

19. Carpentry Defects in Timber
Upsets or.
This defect is caused due to injury suffered by wood fibers by crushing or compression. Upsets are mainly due to improper felling of tree and exposure of tree in its young age to fast blowing wind. This defect indicates change in direction of wooden fibers.
Twisted fibers.
They are caused by twisting of young trees constantly in one direction under the action of strong prevalent winds. Timber with twisted fibers is unsuitable for sawing. The timber having this defect is mostly used for posts and poles in an unsawn condition

20. Carpentry Defects in Timber
Upsets or.
This defect is caused due to injury suffered by wood fibers by crushing or compression. Upsets are mainly due to improper felling of tree and exposure of tree in its young age to fast blowing wind. This defect indicates change in direction of wooden fibers.

21. Carpentry Defects in Timber
Knots. Knots are generally developed at the bases of branches cut off from the tree. This phenomenon ultimately results in the formation of dark, hard rings, known as knots. As knots break the continuity of the wooden fibers, they form a source of weakness. The amount of weakness caused by the knot depends upon the position, size, and degree of grain distortion around it. Knot is the most commonly encountered defect of wood.

22. It is impossible to procure timber free of knots.
Knots may be dead, live loose,
or tight. Tight knots are not
objectionable unless they
are too large. Their presence on
tension members is objectionable
. It is very difficult to plane
the timber at knots.

23. Carpentry Defects in Timber
Wind cracks. The outer layers of a standing tree suffer from the effect of shrinkage due to atmospheric agencies. This causes cracks on the outer surface only. These cracks are known as wind cracks.

24. Carpentry Methods of stacking.
Before seasoning, the timber should be stacked in yards so as to protect the timber from direct sun.
Ends of logs should be protected against splitting by applying anti-Splitting compositions and stacked on foundations in closed stacks in one or more layers.

25. Carpentry Defects in Timber
One and nine method of stacking.
This method of stacking timber is most suitable for moderately heavy coniferous sleepers in hot climates and for heavy timbers in moist climates. For reference

26. Carpentry Defects in Timber
Close crib method.
This method of stacking timber allows reduced air circulations and thus slows down the pace of seasoning. This method is recommended for stacking heavy structural timbers like sal in hot and dry localities.

27. Carpentry Defects in Timber
Doors
Joinery works shall be carefully put together and properly jointed in accordance with best practice; all joints shall be glued and screwed or doweled. Any screws appearing on face work shall have the heads let in and be pelted unless otherwise described.
Softwood fixings shall be about steel screws.
Hardwood joinery shall be put together and fixed brass cups and screws.
Cups for fixing hardwood joinery shall be cast brass cups with milled edges and shall be neatly let in to finish flush with the face of the work.

28. Paneled doors

29. Flush doors

30. Carpentry Defects in Timber
Frames
Frames to doors, windows and fly screens shall be provided and built in to the sizes Frames shall be securely tied to walls by means of steel or similar metal cramps, galvanized or dipped in bitumen as follows:
Door frames: Three cramps to each side.

31. Window frames: Two or more cramps to each side according to size.
Doors, windows, etc shall be carefully and accurately fitted to the frames to give a uniform clearance of not more than 3mm all rounds.
Glazed beads where required shall be wrought splayed and rounded and shall be neatly mitered and fixed with small brads or lost-head nails.

35. Carpentry
End