BUILDING MATERIALBUILDING MATERIAL

PALESTINE UNIVERSITY PALESTINE UNIVERSITY

Chapter No. 4Chapter No. 4

TimberTimber

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

Carpentry Carpentry GeneralGeneral

Timber is obtained from trees. Timber denotes structural Timber is obtained from trees. Timber denotes structural wood. A standing living tree is known as standing wood. A standing living tree is known as standing timber.timber.Rough timber.Rough timber.

When tree has been cut and its stem and branches When tree has been cut and its stem and branches are roughly converted into pieces of suitable lengths.are roughly converted into pieces of suitable lengths.Converted timber

When roughly converted timber is further sawn When roughly converted timber is further sawn and converted into commercial size the planks, logs, and converted into commercial size the planks, logs, battens, posts, beams, etcbattens, posts, beams, etc

It is easily available every where.It is easily available every where. Its salvage value is high.Its salvage value is high. It can be easily transported by converting large It can be easily transported by converting large

pieces into smaller pieces.pieces into smaller pieces. Working on timber is easy. Timber constructions Working on timber is easy. Timber constructions

can be easily repaired. Additions and alterations to can be easily repaired. Additions and alterations to timber structures can be easily done.timber structures can be easily done.

It can be easily jointed.It can be easily jointed. In marine works, timber is considered as an ideal In marine works, timber is considered as an ideal

material as it does not corrode. Cement and iron material as it does not corrode. Cement and iron structures corrode in sea water, if they are not structures corrode in sea water, if they are not protected with special preservative.protected with special preservative.

Carpentry Carpentry Advantages of TimberAdvantages of Timber

Being light in weight, it is preferred for building Being light in weight, it is preferred for building works in earth quake prone regions.works in earth quake prone regions.

It is an excellent material for decorative and general It is an excellent material for decorative and general use furniture. Lot of other internal decorations can use furniture. Lot of other internal decorations can be carried out with it.be carried out with it.

It can with stand, shocks better than iron and It can with stand, shocks better than iron and concrete.concrete.

It is good insulator of electricity and heat.It is good insulator of electricity and heat. It is good sound absorbing material.It is good sound absorbing material. Timber can be easily strengthened by attaching Timber can be easily strengthened by attaching

steel or other material with it. steel or other material with it.

Carpentry Carpentry Advantages of TimberAdvantages of Timber

It can be said that there is no Engineering field, It can be said that there is no Engineering field, where timber is not used one way or the other.where timber is not used one way or the other.

Uses of timber are numerous. Some of its important Uses of timber are numerous. Some of its important uses are given as follows:uses are given as follows:

It is very much used for railway track sleepers.It is very much used for railway track sleepers. It can be used inform of piles, vertical posts, beams, It can be used inform of piles, vertical posts, beams,

lintels, doors and windows.lintels, doors and windows. It can also be used as members of roofing trusses.It can also be used as members of roofing trusses. It is an important material for furniture-makingIt is an important material for furniture-making It is used for floors, ceiling, and partition walls.It is used for floors, ceiling, and partition walls.

Carpentry Carpentry Use of TimberUse of Timber

It is used as form-work for cement concrete It is used as form-work for cement concrete structures. structures.

It is very much used in making sports. goods, It is very much used in making sports. goods, musical instruments, well curbs, agricultural musical instruments, well curbs, agricultural

implements, etc.implements, etc. Packing cases are mostly made from soft timber.Packing cases are mostly made from soft timber.

It is very much used for timbering the deep. It is very much used for timbering the deep. trenches.trenches.

Railway coaches and wagons are also made from Railway coaches and wagons are also made from high class timber.high class timber.

Carpentry Carpentry Use of TimberUse of Timber

Following are the qualities of good timber.Following are the qualities of good timber. A good timber should be hard and durable.A good timber should be hard and durable.

It should be capable of resisting the actions of fungi, It should be capable of resisting the actions of fungi, chemicals and physical agencies.chemicals and physical agencies.

The fibers of the timber should be straight and The fibers of the timber should be straight and compact.compact.

The timber should be free from knots, twists, upsets, The timber should be free from knots, twists, upsets, burls shakes, flaws etc.burls shakes, flaws etc.

Its colour should be dark. It should be obtained Its colour should be dark. It should be obtained preferably from heart wood. Colour should be uniform.preferably from heart wood. Colour should be uniform.

It should be properly seasoned.It should be properly seasoned. Its freshly cut surface should smell sweetIts freshly cut surface should smell sweet..

Carpentry Carpentry Qualities of Good TimberQualities of Good Timber

Its weight should be heavy.Its weight should be heavy.It should be easily workable. It should not clog the teeth of It should be easily workable. It should not clog the teeth of

sawsawand should be capable of being easily planned.and should be capable of being easily planned.

Timber should be tough i.e., it should be capable of resisting Timber should be tough i.e., it should be capable of resisting shocks.shocks.

It should be able to withstand the weathering affects.It should be able to withstand the weathering affects.It should be strong enough to withstand bending, direct and It should be strong enough to withstand bending, direct and

shear effects efficiently.shear effects efficiently.A clear ringing sound should be emitted by the timber when A clear ringing sound should be emitted by the timber when

struck. Heavy dull sound indicates decayed timber.struck. Heavy dull sound indicates decayed timber.It should offer adequate fire resistance.It should offer adequate fire resistance.

It should be elastic It should be elastic

Carpentry Carpentry Qualities of Good TimberQualities of Good Timber

The defects that usually occur in the timber may be The defects that usually occur in the timber may be

classified into two categories as follows:classified into two categories as follows:

Defects that develop during growth of the tree.Defects that develop during growth of the tree.

Defects that develop after felling the tree.Defects that develop after felling the tree.

Carpentry Carpentry Defects in TimberDefects in Timber

Defects that develop during growth of tree Defects that develop during growth of tree have been briefly discussed as follows:have been briefly discussed as follows:

Shakes. This is most serious type of defect in timber. Shakes. This is most serious type of defect in timber. These are sort of cracks which partly or completely These are sort of cracks which partly or completely separate the fibers of wood. A shake is nothing, but separate the fibers of wood. A shake is nothing, but

separation of the timber along the grains. Shakes separation of the timber along the grains. Shakes may be of several types.may be of several types.

Carpentry Carpentry Defects in TimberDefects in Timber

Carpentry Carpentry Defects in TimberDefects in TimberStar shakesStar shakes. .

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

Carpentry Carpentry Defects in TimberDefects in Timber

Heart shakes.Heart shakes.

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

Carpentry Carpentry Defects in TimberDefects in Timber Cup shakesCup shakes. .

This defect develops curved slit This defect develops curved slit

between successive annual rings. The between successive annual rings. The

split does not run for the full split does not run for the full

circumference of the annual rings. This circumference of the annual rings. This

defect usually develops due to unequal defect usually develops due to unequal

growth. Another possible reason for their growth. Another possible reason for their

development may be contraction of development may be contraction of

timber under atmospheric changes timber under atmospheric changes

together with the twisting action of together with the twisting action of

strong winds.strong winds.

Carpentry Carpentry Defects in TimberDefects in Timber Ring shakes.Ring shakes.

When cup shake defect runs for full When cup shake defect runs for full circumference of the annual ring, it is called circumference of the annual ring, it is called

ring shake. It is more serious than cup shake.ring shake. It is more serious than cup shake.

Radial shakes.Radial shakes.

They are similar to star shakes. They They are similar to star shakes. They are numerous, fine and irregular. They are numerous, fine and irregular. They

usually occur when felled tree is usually occur when felled tree is exposed to sun for seasoning. The exposed to sun for seasoning. The

cracks run for a short distance from cracks run for a short distance from bark to-wards the centre and then bark to-wards the centre and then

follows the course of an annual ring follows the course of an annual ring and ultimately goes towards the pith.and ultimately goes towards the pith.

Carpentry Carpentry Defects in TimberDefects in TimberUpsets or.Upsets or.

This defect is caused due to injury suffered by wood This defect is caused due to injury suffered by wood fibers by crushing or compression. Upsets are fibers by crushing or compression. Upsets are

mainly due to improper felling of tree and exposure mainly due to improper felling of tree and exposure of tree in its young age to fast blowing wind. This of tree in its young age to fast blowing wind. This

defect indicates change indefect indicates change in direction of wooden direction of wooden fibersfibers..

Twisted fibersTwisted fibers..

They are caused by twisting of young trees constantly They are caused by twisting of young trees constantly in one direction under the action of strong prevalent in one direction under the action of strong prevalent

winds. Timber with twisted fibers is unsuitable for winds. Timber with twisted fibers is unsuitable for sawing. The timber having this defect is mostly used sawing. The timber having this defect is mostly used

for posts and poles in an unsawn condition for posts and poles in an unsawn condition

Carpentry Carpentry Defects in TimberDefects in Timber

Upsets or. Upsets or.

This defect is caused due to This defect is caused due to injury suffered by wood fibers injury suffered by wood fibers

by crushing or compression. by crushing or compression. Upsets are mainly due to Upsets are mainly due to

improper felling of tree and improper felling of tree and exposure of tree in its young exposure of tree in its young

age to fast blowing wind. This age to fast blowing wind. This defect indicates change in defect indicates change in

direction of wooden fibers.direction of wooden fibers.

Carpentry Carpentry Defects in TimberDefects in Timber

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

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

Carpentry Carpentry Defects in TimberDefects in Timber

Wind cracks. The outer Wind cracks. The outer layers of a standing layers of a standing tree suffer from the tree suffer from the effect of shrinkage effect of shrinkage due to atmospheric due to atmospheric

agencies. This causes agencies. This causes cracks on the outer cracks on the outer surface only. These surface only. These

cracks are known as cracks are known as wind cracks.wind cracks.

Carpentry Carpentry Methods of stacking.Methods of stacking.

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

Carpentry Carpentry Defects in TimberDefects in Timber

One and nine method of One and nine method of stacking.stacking.

This method of stacking This method of stacking timber is most timber is most

suitable for suitable for moderately heavy moderately heavy

coniferous sleepers in coniferous sleepers in hot climates and for hot climates and for

heavy timbers in heavy timbers in moist climates. For moist climates. For

reference reference

Carpentry Carpentry Defects in TimberDefects in Timber

Close crib methodClose crib method. .

This method of This method of stacking timber allows stacking timber allows

reduced air reduced air circulations and thus circulations and thus slows down the pace slows down the pace

of seasoning. This of seasoning. This method is method is

recommended for recommended for stacking heavy stacking heavy

structural timbers like structural timbers like sal in hot and dry sal in hot and dry

localities.localities.

Carpentry Carpentry Defects in TimberDefects in Timber

DoorsDoors

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

Paneled doors

Flush doors

Carpentry Carpentry Defects in TimberDefects in Timber

FramesFrames

Frames to doors, windows and fly screens shall be Frames to doors, windows and fly screens shall be

provided and built in to the sizes Frames shall be provided and built in to the sizes Frames shall be

securely tied to walls by means of steel or similar metal securely tied to walls by means of steel or similar metal

cramps, galvanized or dipped in bitumen as follows:cramps, galvanized or dipped in bitumen as follows:

Door frames: Three cramps to each side.Door frames: Three cramps to each side.

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

EndEnd

Carpentry Carpentry