General Information :-
Lumber (American English) or timber (British English) is a collective term for harvested wood that has been manufactured into boards and planks. Lumber is predominantly used for structural purposes but has many other uses as well. Lumber is classified as hardwood or softwood.
Most timbers show variation in color between species and within species. Timber exposed to light will change color and unprotected timber, exposed to the weather, will eventually become silver grey in color.
In timber Grain refers to the general direction, size and arrangement of the wood cells, and may be used to broadly describe the timber’s appearance.
Meanwhile, the timber’s texture may be described as being 4 different types such as :-
- even or
This differentiation between coarse and fine texture is made on the basis whereas hardwoods may span the range from Coarse to Fine.
The main factors affecting density are the size of the cells (including cell wall thickness), In general terms, density is one of the most reliable indicators of strength, as well as several other properties, such as stiffness, joint strength, hardness, ease of machining, fire resistance and drying characteristics.
Timber is graded for the following reasons:-
- For Structural Performance ;
- For Appearance
There are 2 basic grading classifications:-
- Structural, for engineering applications such as beams and framing.
This can be done by visual stress grading or by machine.
- Stress grading, and acoustic stress grading appearance, for cladding, flooring, panelling, finishing, furniture and fittings.
Example of Structural Strength Table:
American grade standards
Quality standards for lumber supplied in American Dimensions shall be with reference to the American Western Lumber Grading Rules for Ponderosa written by WWPA Sept 1991.
Thicknesses supplied in KD sawn form in American Dimensions are based on the following sizing:
- 5/4 stock is 40mm green sawn measure and is invoiced at 32mm 6/4 stock is supplied at 46mm green sawn measure and is invoiced at 38.1mm
- Measurement of lumber supplied under American Western Lumber Grading Rules written by WWPA Sept 1991 shall be in the US form of Metric Board Feet Mfbm (1000 board feet) with conversion to Cubic Meters on the following basis: Scaling of Random Width boards in US form in Mfbm (1000 board feet) and divided by .424 to calculate and convert to Cubic Meters(M3) thus 1 mfbm =2.358 M3
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