TIMBER

 Timber means wood which is suitable for building or carpentry or    various other engineering purpose.

•   converted timber- Timber which is Shawn and cut into suitable            commercial sizes
•   Rough timber - Timber which is obtaining after felling tree.
• Standing timber - timber contained in a living tree.

property

• low heat conductivity .
• amenability to mechanical working.
• small bulk density.
• relatively high strength.

Drawbacks

• susceptibility to decay and inflammability.
• fluctuation in properties due to change in moisture content.
• variation in strength in length and across fibers.
• effective utilization of wood waste i.e, sawdust and shavings are used with admixture of organic glues to make fiber slab, fiber boards etc.

Uses

• organic acid 
• rosin
• paper
• cardboard
• cellulose
• consumption of wood in building industry should be carried out in the best possible economy way.

Power of tree

• it conserves soil moisture.
• it precipitates rainfall and lower temperature.
• it prevents depletion of the ozone layer of atmosphere.
• it prevent soil erosion .
• it produces oxygen and purifies the air.

TIMBER HOUSE

CLASSIFICATION OF TREES

• Exogenous Tree: - These trees increases in bulk by growing outwards and distinctive consecutive rings are formed in the horizontal section of such a tree. These rings are known as the annual ring. Because one such ring is added every year & these rings are useful in predicting the age of tree.
• Conifers :- 

1. evergreen tree and leaves of these trees do not fall till new ones are grown 
2. yield soft wood 
3. light colored, resinous,light in weight and weak.
4. they show distinct annual ring.

• Deciduous tree :-

1. broad leaf tree
2. leaves of these trees fall in autumn and new ones appear in spring season.
3. hard wood which are usually close grained.
4. strong , heavy dark colored, durable and non resinous.
5. they do not show distinct annual ring.

• Endogenous Tree :- these tree grow inward and fibrous mass is seen in their longitudinal section.the timber from these trees has very limited engineering application . Eg. bamboo tree, cane, palm etc.

• Structure of a Tree :-  consist of three parts.

1. roots
2. trunk
3. crown

• The structure of a tree can be divided into two categories

1. macro structure
2. micro structure

• Macro Structure :-

 .

Sequences:-(from outer to inner)

1. outer bark
2. inner bark
3. cambium layer
4. sap wood 
5. heart wood 
6. pith 
7. medullary rays

1. Outer Bark :-  It consist of cells of wood fiber and is also known as cortex. The outer skin or cover of the tree is known as the outer bark.
2. Inner Bark :-  it gives protection to the cambium layer from any injury .
3. Cambium layer :- it indicate sap which has yet not be converted into sap wood . if the bark is removed for any reason, the cambium layer gets exposed  and the cells cease to be active resulting in the death of tree.
4. Sap Wood :- it is usually light in color as well as light in weight. The annual rings of sap wood are less sharply defined than those of heart wood . it takes active part in the growth of tree and the sap moves in an upward direction through it.
5. Heart Wood :- it usually dark in color & it indicates dead portion of tree. it does not take active part in the growth of tree but it imparts rigidity to the tree and hence it provide strong and durable timber for various engineering properties.
6. Pith :- (core of the tree) -It consists entirely of cellular tissues and it nourishes the plant in its young age. when the plants becomes old, the pith dies up and decays & the sap is then transmitted by the woody fibers deposited round the pith . the pith of branches is nothing but merely a prolongation of the pith of stem.
7. Medullary Rays :- The thin radial fibers extending from pith to cambium layer are known as medullary rays. the function of these rays is to hold together the annual ring of heart wood and sap wood .

• Micro Structure :- when studied under a microscope , it becomes evident that wood consist of living and dead cells of various sizes and shapes.

       The living cell consist of four parts

1. membrane 
2. protoplasm
3. sap
4. core

The cells, According to function.

1. conductive cells
2. mechanical cells 
3. storage cells 

1. Conductive Cells:- these cells serve mainly to transmit nutrients from roots to the branches and leaves.
2. Mechanical Cells:- These cells impart strength to the wood .
3. Storage Cells :- These cells serve to store and transmit nutrients to the lining cell in the horizontal direction and they are usually located in the medullary rays.

• Processing of Timber :- 

1. felling of trees
2. seasoning of timber
3. conversion of timber
4. preservation of timber