BUILDING MATERIALS AND CONSTRUCTION

TIMBER

Team Members

Anugraha N

Grace Henry

Jidhin Janardhanan

Navami C.G

Neha Suresh

Tomin George

TIMBER • The wood which is suitable or fit for

engineering construction or engineering purpose is called timber

• It should have structural as well as aesthetic merits.

Name origin

To buildTimbrian(English word)

Timber

USES OF TIMBER

• BUILDING CONSTRUCTION• HOUSE POST CONSTRUCTION• BEAMS AND RAFTERS

• CONSTRUCTION OF BRIDGES AND BOATS• FURNITURE AND INSTRUMENTS

• RAILWAY SLEEPERS AND PACKING CASES• TOYS AND ENGRAVING WORK• RAILWAY COACH WAGONS

• FORMWORK OF CEMENT CONCRETE

General PropertiesColor – a darker color in wood indicates greater durability.Odor – it is present only on freshly cut trees.Hardness – is the ability of wood to withstand indentations caused by harder

bodies.Density – densest woods are generally the strongest.Grain - Depending on the actual alignment, the grain may be straight, spiral,

interlocked, wavy or irregular.a) Spiral Grainb) Interlocked Grainc) Wavy GrainTexture - In hardwoods, the texture depends upon the size and distribution vessels

and rays. In softwoods, it is determined by the size and distribution of tracheid.

Identifications of Timber

Luster- is the ability to reflect light beam pointedly. Workability- the relative case in which wood is shaped cut and fastened

together than the others.Warping- is the general term used to describe any variation from a true

surface.Moisture content- is a percentage of the mass of water over the mass of

wood fibre in a piece of timber.Specific Gravity- is the ratio found by dividing the weight of a substance by

the weight of an equal volume of pure water.

Moisture of Timber• Moisture Content - It is one of the most important

characteristics of timber that affects its use on the site performance.

• Equilibrium Moisture Content (EMC) - moisture content of wood changes in response to the temperature and humidity of its surroundings.

• Fibre Saturation Point (FSP) – when the cell cavities are empty but the cell walls still retain their bound water.

SEASONING

• Fresh timber which is obtained from trees have about 30 to 40 percent sap or moisture. This sap is very harmful for the life of the timber.

• Therefore it is essential to remove the sap by applying certain special methods.

• All such methods are collectively termed as seasoning of timber.

TYPES OF TIMBER SEASONING

Timber seasoning

Artificial seasoning Water seasoning

Natural seasoning

NATURAL SEASONING

Artificial seasoning Kiln seasoning

Chemical seasoning

Electric seasoning

Advantages of seasoned timber

• It has reduced weight• Strong and durable • Resistance to decay and rot • Takes high polish• Easier to work with• Lasts longer

Defects in timber

Defects caused in timber may be basically classified into two categories:

Internal Defects – due to factors affecting the growing tissue or the tree.

External Defects – due to external agents or subsequent treatment of timber.

Defects in Timber

• The defects occurring in the timber are grouped as follows :-

1. Defects due to conversion2. Defects due to fungi3. Defects due to insects4. Defects due to natural forces5. Defects due to seasoning

Defects due to conversion• During the process of converting timber to the

commercial form, the following defects occur:-a) Chip mark- marks or signs placed by chips on the

finished surface of timber.b) Diagonal grain- Due to improper sawing of timber.c) Torn grain- Caused when a small depression is

formed by falling of a tool or so.d) Wane- Denoted by the presence if original rounded

surface on the manufactured piece of timber.

Defects due to fungi

Fungi attack timber only when the following two conditions are satisfied simultaneously:i. The moisture content of timber is above 20%.ii. There is presence of air and warmth for the growth of fungi.

Following defects are caused in the timber by the fungi:• Blue stain- sap of wood is stained to bluish color.• Brown rot-decay or disease of timber.• Dry rot- converting of timber into dry powder form.• Heart rot- indicated by the hollow sound given out when struck

with a hammer.• Sap strain-loses the color of sap.• Wet rot- causes chemical decomposition of wood of timber.• White rot- opposite of brown rot.

Defects due to insects and natural forcesInsects which are usually responsible for the decay of timber:-• Beetles• Marine borers• TermitesNatural forces causes:• Abnormal growth• Rupture of tissues

Defects due to natural forces

• Burls- growth of the tree is upset and irregular projections appear.• Callus- soft skin which covers the wound of the tree.• Chemical stain- discoloring of wood.• Coarse stain- annual rings get widened.• Dead wood- timber obtained from dead trees.• Druxiness- white decayed spots which are concealed by healthy wood.• Foxiness- indicated by red or yellow tinge in wood.• Rind galls- these are typical curved swelling formed upon the trunk of the tree by

successive layer of the sapwood.• Twisted fibers- fibers or wandering hearts are caused by the prevalent wind turning

or twisting the tree at its young age constantly in one direction.• Upsets- are clipping or buckling of fibers caused by crushing of fibers when the trunk

is felled violently over a rocky surface.• Water stain-• Wind cracks- are shakes on the outside of a log due to the shrinkage of the exterior

surface caused by the atmospheric influences.

Defects due to seasoning

Following defects occur in the seasoning process of wood:

• Bow- a curvature of the timber in the direction of its length.• Case-hardening- it is due to the unequal drying of the exterior surfaces

under compression and the interior surfaces under tension due to rapid drying.

• Check - these reduce the shearing resistance of the wood.• Collapse - the cells of timber are flattened due to excessive shrinkage.• Cup- a curvature in the transverse direction of the timber.• Honey-combing- separation of the fibers in the interior due to drying

stresses.• Radial shakes• Split- separation of the fibers along the grain and extends from one end

of the plank to the other.• Twist- a spiral distortion along the length of the timber. • Warp

Knots• Knots - are dark, hard pieces occurring as signs of branches broken or cut off.

According to size (diameter) Pin Knot – not more than 6.5mm Small Knot - more than 6.5mm but not more than 20mm Medium Knot- more than 20mm but not more than 40mm Large Knot- more than 40mm

According to form Round or Oval Knot- a knot cut more or less at right angles to its long axis so that the exposed is round or oval. Splay or Spike Knot- a knot cut approximately parallel to its long axis so that the exposed section has an

elongated shaped.

According to quality Live Knot- a knot whose fibers are completely intergrown with those of the surrounding wood. Sound Knot- a live knot free from decay. Tight Knot- a live or dead knot held firmly in place Dead Knot- a knot whose fibers are not intergrown with those of the surrounding wood. According to quality Loose Knot- a dead knot which is not held firmly in place. Knot Hole- a hole left as results of the removal of a knot. Decayed Knot- a knot softer than the surrounding wood, and containing decay.

Shakes

• Shakes- or cracks are caused by the rupture of tissues resulting in partial or complete separation of the fibers along the grain.Star ShakesHeart Shakes Cups ShakesRing Shakes Radial Shakes

Objects of preservation of timber

• The preservation of timber is carried out to achieve the following three objects:-

• To increase the life of timber structures.• To make the timber structures durable.• To protect the timber structures from the attack of

destroying agencies such as fungi, insects, etc.

TIMBER PRESERVATIVES

The main classes of timber preservatives are :• Ascu treatment• Chemical salts• Coal tar is highly effective against fungi.• Cresote oil• Oily substances insoluble in water• Water soluble salts Zinc chloride is the most extensively used of this type. It is clean and odourless.

Availability and uses of timber

• Common TimberTeak - The sapwood is pale yellowish or greyish-white in color and is distinguished from

heartwood. The heartwood is golden brown and turns a dull deeper brown on exposure.Deodar - The sapwood is white to creamy white and is distinct from the heartwood which is

light yellowish brown turning to pinkish brown on exposure.Chir - The sapwood is white to creamy white and is distinct from the heartwood which is light

yellowish brown turning to pinkish brown on exposure.Kail - The yellowish in white to greyish sapwood is white to pale-yellowish white in color and

is distinct from the heartwood which is light pinkish-red to light red. Sisso - Sapwood of sisso is pale yellowish or greyish white and is distinct from the heartwood

which is golden brown or dark brown in color. Sal - The sapwood is pale-yellowish or brownish white and is distinct from the heartwood

which is brown or reddish brown.Mango - This is brown in color.

TIMBER PRODUCED IN INDIA

• There are over 150 species of timber which are produced in India. Following are the chief varieties of timber trees which are used for engineering purposes in India:

• Scientifically prepared timber in a factory.

• They possesses desired shape, appearance, strength, etc.

Industrial timber

Veneers

Plywoods

Fibre boards

Impreg timbers

Compreg timbers

Block board and lamin board

Glulam

Flushdoor shutters

Particle board or clip board

Hardboard

Veneers (IS:303-1989)

• These are thin sheets or slices of wood if superior quality whose thickness varies from 0.40 mm to 6 mm or more.

• They are obtained by rotating a log of wood against a sharp knife of rotary cutter or saw. • The veneers after being removed are dried in kilns to remove moisture.• Veneers may be glued with suitable adhesives on the surface of inferior wood. • Used to produce plywood, batten boards and lamina boards.• May be fixed on corners or bent portions.• Indian timbers suitable are mahogany, oak, rosewood, sissoo, teak, etc.

Plywood

• Plywood is a panel formed of three or more layers of veneer glued together, usually with the grain of adjacent veneers running at right angles to each other, held in position by the application of suitable adhesives.

• The perpendicular placing increases longitudinal and transverse strengths of plywood.• The plywood are available in different commercial forms such as batten board, lamina board,

metal faced plywood, multiply, three-ply, veneered plywood, etc. • According to CPWD specifications, plywood for general purposes are of following three grades:i. Boiling Water resistantii. Warm water resistantiii. Cold water resistant

Thickness

Dimensions (sizes of plywood)

Tolerance of plywood

Advantages of plywood

It has a good strength both across as well as along the grain.Plywood has better splitting resistance due to grains in adjacent layers running at

the right angle and nailing and screwing even closed to the edges in safe.Can easily be bending to a curvature limited by the tensile and the compressive

strength of the other plies.The face piles made at different heartwoods show great aesthetic variety in grain

pattern and color.

Hardwood• Hardboard - manufactured from raw materials like

wood waste, veneer manufacturing, furniture making. Sizes of hardboards

Medium hardboard Normal hardboard Tempered hardboard Thickness of Hardboards

Width and Length of Hardboards

• Fibre Board: Rigid boards and they are known as the oressed wood or reconstructed wood. The fibre boards form an ideal base for all types f decorative finishes like distemper, oil paint, etc.

• Impreg timbers: Timber which is fully or partly covered with resin and used for moulds, furniture, decorative articles, etc.

• Compreg timbers: Almost with same properties as of above, it is treated under high pressure. The strength and durability is more.

• Block boards or lamin boards: it is a board having core strips, each not exceeding 7 mm in thickness

• Glulam: Glued and laminated wood made of solid wood.• Flush door shutters: More popular for interior works.• Particle boards: is a board manufactured from particles of wood or other

lingo cellulose materials.

BattenBaulkBoardDealEndLogPlankPoleQuarteringScantling

Market forms of timber

Batten has breadth and

thickness which does not exceed 50 mm.

Baulk is a roughly

Squared timber piece and it is obtained by

removing bark and sap wood.

Board is a plank whose

thickness is less than 50 mm and width

exceeds 150 mm.

Deal is a piece of soft wood with parallel

sides which has a width limited upto 230 mm.

End is a short piece of batten, deal, scantling.

Log is a trunk of tree obtained

after removal of branches.

Plank is a timber piece with

parallel sides.

Pole is a sound long log of wood. Also

called as a spar.

Quartering is a square piece of

timber.

Scantling are the pieces if

miscellaneous sizes of timber sawn out of a

log.

Joineries• Joinery is a part of woodworking that involves joining together pieces

of timber or lumber, to produce more complex items. Some wood joints employ fasteners, bindings, or adhesives, while others use only wood elements. The characteristics of wooden joints - strength, flexibility, toughness, appearance, etc. - derive from the properties of the materials involved and the purpose of the joint. Therefore, different joinery techniques are used to meet differing requirements. For example, the joinery used to construct a house can be different from that used to make puzzle toys, although some concepts overlap.

Joint ExplanationButt Joint The end of a piece of wood is butted against another piece of wood. Simplest and weakest joint.Lap Joint The end of a piece of wood is laid beside and connected to another piece of wood. The next simplest and

weakest joint.Bridle Joint This joint is where the through mortise is open on one side and forms a fork shape. The mate has a through

tenon or necked joint. Used to join rafter tops, scarf joints and sill corner joints in timber framing.Dowel Joint The end of a piece of wood is butted against another piece of wood. A very common joint in factory-made

furniture.Mitre Joint Similar to a butt joint, but both pieces have been beveled.Finger Joint Also known as a box joint, is a corner joint with interlocking fingers. Receives pressure from two directions.Dovetail Joint A form of box joint where the fingers are locked together by diagonal cuts. More secure than a finger joint.

Dado Joint Also called a housing joint or trench joint, a slot is cut across the grain in one piece for another piece to set into.

Groove Joint Like the dado joint, except that the slot is cut with the grain.Tongue and Groove Each piece has a groove cut all along one edge, and a thin, deep ridge (the tongue) on the

opposite edge.

Mortice and Tenon A stub (the tenon) will fit tightly into a hole cut for it (the mortise). The traditional method of jointing frame and panel members in doors, windows, and cabinets.

Birdsmouth Joint Also called a bird's beak cut, this joint used in roof construction. A V-shaped cut in the rafterconnects the rafter to the wall-plate.

Cross Lap A joint in which the two members are joined by removing material from each at the point of intersection so that they overlap.

Splice Joint A joint used to attach two members end to end.

Malaysian woodMalaysia wood is actually RUBBER WOOD or Hevea Brasiliensis. Rubber wood is durable & high density. It is best to use on furniture.

Heavy Hardwood- Chengal

• Chengal is considered the number one wood (classified as heavy hardwood) of Malaysia and export of logs is prohibited due to its scarcity.

• Planing is known to be easy and a smooth finish is easily achieved• Boring is not hard• Turning is easy as well and a smooth finish is achieved• Nailing is very difficult and mostly a hole has to be predrilled to receive a nail• The timber is classified as naturally durable and is normally very resistant to

termite attack and fungal infestation .

• The timber is suitable for all forms of heavy construction, railway sleepers, heavy duty furniture, laboratory benches, bridges, marine construction, boat building, telegraphic and power transmission posts and cross arms, piling, mallets, flooring (heavy traffic), decking, vehicle bodies (framework and floor boards), fender supports, cooling towers (structural members), staircase (balusters, carriages, handrails, newels, risers, stringers, treads, bullnoses, round ends and winders), columns (heavy duty), door and window frames and sills, tool handles (impact), carving works and other uses where strength and durability are required.

• On the Malay Peninsula Chengal has been used as the wood of choice for house and boatbuilding. It is sometimes referred to as the "Malaysian Teak".

Keruing- Middle Hardwood• Keruing is the name given to the timber yielded from more than 70 species of

the genus Dipterocarpus. This group of large hardwoods is indigenous to South East Asia, where the species are harvested from managed forests with regeneration programs.

• Keruing timber is low maintenance, hardwearing and ideal for outdoor furniture use. The wood is strong and classified as durable, making it useful for construction purposes. Other common uses include internal flooring, protected framing and boards, internal joinery and mouldings, lining, paneling and framework. Preservative-treated material is used for poles, piles, sleepers and cross-arms. It is often used as a cheaper alternative to oak for heavy construction, decking, vehicle building and sleepers, and it is also in plywood.

• Across this entire species of keruing, a wide variety of heartwood hues are available, including deep-pink, orange-pink, and purple-red. The most common heartwood is red-brown.

Malaysian Rubber wood

• Rubber wood is a light-colored medium-density tropical hardwood obtained from the Pará rubber tree (Hevea brasiliensis), usually from trees grown in rubber plantations.Rubberwood is commonly advertised as an "environmentally friendly" wood, as it makes use of plantation trees that have already served a useful function.

• In 2002, the Malaysian Ministry of Primary Industries marketed it under the name "Malaysian Oak.

• Rubberwood has a dense grain that is easily controlled in the kiln drying process. Rubber-wood has very little shrinkage making it one of the more stable construction materials available for furniture, toys and kitchen accessories. It is easily worked, and takes on stains uniformly. As with all hardwoods, rubberwood comes in varying degrees of quality.

• It is not suitable for outdoor use, as rain can leach the protective chemicals from the wood, exposing it to fungus and insect attacks. Excessive moisture will also cause the wood to warp and rot.

ADVANTAGES OF TIMBER Can be easily handled and joined. Timber can be used for both load bearing structures and non-load bearing instruments. It can be easily converted to any shape and size. With the advent of superior adhesives and other forms of timber connectors. The wastage in timber construction is less because all wastes can be put one use or the

other. It has high resale and salvage value.

Timber has better insulating properties than any other materials.

Durability of timber can be very high, if properly seasoned and preserved.

Timber constructions are light in weight and strong and can be made economical.

For aesthetic and decorative appearance.

Easily available.

High energy efficiency.

Sources

• Wikipedia, the free encyclopedia• Google images• Malaysian timber board official website• Building Materials by Rangwala

THANK YOU ……