Bradly wood is the hard material which retina underneath the bark of the tree. Timber is the main portion of wood which can retain its structure.
Timber is the natural material obtained from wood. The wood may be chemically and mechanically treated to create synthetic wooden materials which has superior quality than the timber, plywood, compressed wood fibre boards are the examples.
Wooden materials are widely used as door, window frame, partition walls and for form work of construction works.
Wood has good property of absorbing shock and thermal, sound and electrical resistance is very good, wood is also less prone to chemical attack.
Wood are obtained form –
Exogenous and Endogenous trees – Exogenous trees grows outwards and they made good structural element. They are further sub divide in to – Deciduous and Conifers trees –Deciduous have flat and broad leaves and annular rings are indistinct in these trees. Examples are – oak, maple, shisham etc.
Conifers trees are evergreen throughout the year and they have pointed needle like leaves their annular rings are distinct. Their wood has long and soft fibre with resinous substances. Examples are – deodar, chir, pine etc.
Timber is classified according to IS : 399 and IS 6534
According to IS 6534 Timber may be classified by grade A, grade B, grade C and grade D method. Grade D method being used internationally.
On the basic of modulus of elasticity (E) timbers are of –Grade A, Grade B and Grade C-
Grade – A E >12.5 KN/mm2,
Grade B E>9.8 <12.5 KN/mm2
Grade B E>5.6 KN<9.8 KN/mm2
On Basis of Durability they are classified as –
High Durability > 120 months life span.
Moderate 60 months to 120 months life span.
Low durability – life span being less than 60 months
How to know if a timber is of good Quality.
The principal properties of a good timber are-
- Annular rings should be spaced closer, more closer being greater strength.
- Medullary rays should be compact.
- Colour and uniform texture.
- Sweet smell when cut fresh.
- Free from any defects.
- Good metallic sound should be produced when struck with any object.
- Good unit weight.
What is seasoning of Timber –
The timber from fresh cut tree has a lot of moisture in it and is not suitable for using as building materiel so its moisture content is reduced to desired level.
The process of reducing the moisture content to desired level is call seasoning of timber.
Seasoning reduces the shrinkage and warping after its placement,
Reduces its tendency to split and decay due to fermentation.
Make timber suitable for painting
Reduces unit weight of timber.