TIMBER
Wood is a solid material derived from woody plants, notably trees but also shrubs. Wood from the latter is only produced in small sizes, reducing the diversity of uses.
Wood has been used for millennia for many purposes. One of its primary uses is as fuel. It is also used as for making artworks, furniture, tools, and weapons, and as a construction material.
Wood has been an important construction material since humans began building shelters, houses, boats. Nearly all boats were made out of wood till the late 1800s. It remains in common use today for some boats and houses. In buildings made of other materials, wood will still be found as a supporting material, especially in roof construction and exterior decoration.
Lumber classification
Hardwood, furniture and fixtures
Softwood, doors, cabinets, etc
Yard lumber, building n industrial work, for framework (2x4s, 2x6s, 2x8s, 2x10s, 2x12s and all others).
Structural timbers, sizes over 6 inches wide and thick
Grading
1. Defect and blemishes
A defect is considered to be any irregularity found in or on a piece that would lower its strength or durability.
Knots,
Splits,
Shakes
Checks
Cross grain
2. Quality
Clear of any knots
Seasoned, air dried, 12-17% moisture content
Kiln dry, less than 12% moisture
Blemish, any mars, scratches, not classified as defects.
A knot is a particular type of imperfection in a piece of timber, which reduces its strength, but which may be exploited for artistic effect. In a longitudinally-sawn plank, a knot will appear as a roughly circular "solid" (usually darker) piece of wood around which the roughly parallel fibres of the rest of the "flows" (parts and rejoins).
Faces and surfaces
Bark side, grain does not raise
Pith side, grain raises
Face
Edge
Dressed
Rough, lumber not dressed
Re-sewn
Textured, various special treatments which imparts relief texture,
S.4S., dressed all 4 surfaces
S.2S., dressed all 2 surfaces
S.1S., dressed on 1 surface
Sizes
The nominal size of a board varies from the actual size of the board. This is due to planing and shrinkage as the board is dried. This results in the final lumber being slightly smaller than the nominal size. Also, if the wood is surfaced when it is green, the initial dimensions are slightly larger (e.g. 1/16″ bigger for up to 4″ nominal lumber, ⅛″ for 5″ and 6″ nominal lumber, ¼″ bigger for larger sizes). As the wood dries, it shrinks and reaches the specified actual dimensions.
The timber industry states that finishing and drying the lumber results in the nominal size differing from the actual size, however, you will find that many houses built more than roughly 50 years ago usually have timber where the actual size and nominal size are the same. This has allowed new construction to become less expensive without having to modify municipal, state, and national building codes.
Non-North American sizes
Examples of Dimensional Lumber Sizes (Softwood and Hardwood)
Inch name
Sawed
Swedish
Australian
2 × 4
50 × 100 mm
45 × 95 mm
45 × 90 mm
1 × 3
25 × 75 mm
22 × 70 mm
19 × 70 mm
3 × 3
75 × 75 mm
70 × 70 mm
70 × 70 mm
2 × 7
50 × 175 mm
45 × 170 mm
Not used
2 × 3
50 × 75 mm
45 × 70 mm
45 × 70 mm
1 × 4
25 × 100 mm
22 × 95 mm
19 × 90 mm
1 × 5
25 × 125 mm
22 × 120 mm
19 × 120 mm
2 × 5
50 × 125 mm
45 × 120 mm
45 × 120 mm
Outside North America sizes of timber vary slightly. Sizes are, in some cases, based on the imperial measurement and referred to as such; in other cases the sizes are too far removed from the imperial size to be referred to by imperial measurement. Lengths are sold every 300 mm (a metric approximation of 1′). Common sizes are similar to the North American equivalent; 2.4, 2.7, 3.0, 3.6, 4.2, 4.8, 5.4, 6.0.
