Timber, lumber. The hard fibrous lignified substance under the bark of trees used for building is referred to differently from place to place. In North America the wood used for building is referred to as Any of the framing wood., where as in Australasia it is referred to as timber. So in America you go off to the lumber store to buy a piece of lumber, and in Australasia you go off to the timber yard to buy a piece of timber. When the wood is 1 inch thick (25mm) or less, it is then referred to as a A piece of sawn, or dressed lumber of greater width than thickness. Usually 19mm (3/4") to 38mm (1 1/2") thick and 75mm (3") or more wide..
Millimeter measurements. system
When using the metric system for building, millimetres (Abbreviation for millimeter which is a metric unit of length equal to one thousandth of a meter. 25.4 mm equals one inch.) are the common unit to use. One millimetre is about the thickness of a pin. There are 10 millimetres in a centimetre and 1000 millimetres in a metre.
When using the standard system for building, inches are the common unit to use. One inch is about the thickness of a pack of playing cards. There are 12 inches in a foot and 3 feet (36 inches) in a yard.
Use of ” and ‘ symbols
1′ = 1 foot
1″ = 1 inch
1 x 3 = 3/4″ x 2 1/2″
1″ x 3″ = true 1″ x 3″
Both standard and metric
1 inch = approx 25 millimetres
1 foot = approx 305 millimetres
1 yard = approx 915 millimetres
Actual and nominal (what’s that mean)
It is easy to see why some people get confused when purchasing wood, as when you go to the supplier and ask for a particular stock size, sometimes what you end up with is a different width and thickness than what you asked for.
Why is this?
That’s because most wood is identified by it’s Rough sawn; Not gauged, planed or dressed. size (The rough-sawn size of a piece of lumber. Before the lumber is surfaced, planed or dressed. The nominal size is usually greater than the actual dimension. e.g. 100x50 (2 x 4) actually equals 90x45 (1 1/2" x 3 1/2").) rather than The finished (dressed) size as opposed to the nominal size of a piece of wood. which is smaller due to dressing (planing) and/or drying.
NOMINAL SIZE (also called sawn or rough sawn) is the size of the wood when it is first sawn and is usually in 1″ (25mm) or 2″ (50mm) multiples, such as 100mm x 50mm which is also 2×4 (2 inches by 4 inches in Standard. Feet and inch measurements. or standard measurements) When the sawn wood is seasoned, Surfaced; planed; smooth; even surface; gauged. or planed the size becomes smaller which is the ACTUAL SIZE.
Therefore….. A piece of wood 100×50 (nominal, sawn size) may become approx 90×45 (actual size)
Or the same thing in standard (inches)
A piece of timber 2×4 (nominal, sawn size) may become approx 1-1/2″ x 3-1/2″ (actual size)
Countries that use the metric system put the bigger number first (100×50) and countries that use the imperial or standard system put the smaller number first (2×4).
100×50 is the same as 2×4, the first is in millimetres and the second is in inches.