What is Timber?

Lumber or timber is a term used to describe wood, either standing or that has been processed for use — from the time trees are felled, to its end product as a material suitable for industrial use — as structural material for construction or wood pulp for paper production. In the U.K. and Australia, "timber" is a term also used for sawn wood products (that is, boards), whereas generally in the United States and Canada, the product of timber cut into boards is referred to as lumber. In the United States and Canada sawn wood products of five inches (127 millimeters) (nominal size) diameter or greater are sometimes called "timbers". Lumber is supplied either rough or finished. Rough lumber is the raw material for furniture making and other items requiring additional cutting and shaping. It is available in many species, usually hardwoods. Finished lumber is supplied in standard sizes, mostly for the construction industry, and is primarily one of a few coniferous (needle-bearing) species such as pine, cedar, hemlock, fir or spruce.

Dimensional lumber

Dimensional lumber is a term used in North America for lumber that is finished/planed and cut to standardized width and depth specified in inches.

Softwoods

Softwood Dimensional Lumber Sizes
Nominal	Actual	Nominal	Actual
1 × 2	¾″ × 1½″ (19×38 mm)	2 × 2	1½″ × 1½″ (38×38 mm)
1 × 3	¾″ × 2½″ (19×64 mm)	2 × 3	1½″ × 2½″ (38×64 mm)
1 × 4	¾″ × 3½″ (19×89 mm)	2 × 4	1½″ × 3½″ (38×89 mm)
1 × 6	¾″ × 5½″ (19×140 mm)	2 × 6	1½″ × 5½″ (38×140 mm)
1 × 8	¾″ × 7¼″ (19×184 mm)	2 × 8	1½″ × 7¼″ (38×184 mm)
1 × 10	¾″ × 9¼″ (19×235 mm)	2 × 10	1½″ × 9¼″ (38×235 mm)
1 × 12	¾″ × 11¼″ (19×286 mm)	2 × 12	1½″ × 11¼″ (38×286 mm)
3 × 4	2½″ × 3½″ (64×89 mm)	2 × 14	1½″ × 13¼″ (38×337 mm)
4 × 4	3½″ × 3½″ (89×89 mm)	6 × 6	5½″ × 5½″ (140×140 mm)
4 × 6	3½″ × 5½″ (89×140 mm)	8 × 8	7¼″ × 7¼″ (184×184 mm)

Examples of common sizes are 2×4 (also two-by-four and other variants such as four-b'-two in Australia), 2×6, and 4×4. The length of a board is usually specified separately from the width and depth. It is thus possible to find 2×4s that are four, eight, or twelve feet in length. In the United States the standard lengths of lumber are 6, 8, 10, 12, 14, 16, 18, 20, 22, and 24 feet.

Solid dimensional lumber typically is only available up to lengths of 24′, yet since builders have a need for lengths beyond that for roof construction (rafters), builders use "finger-jointed" lumber that can be up to 36′ long in 2×6 size (see Engineered Lumber below). Finger-jointed lumber is also widely used for smaller lengths like studs, the vertical members of a framed wall. Pre-cut studs save a framer a lot of time as they are pre-cut by the manufacturer to be used in 8′, 9′ & 10′ ceiling applications, which means they have removed a few inches of the piece to allow for the sill plate and the double top plate with no additional sizing necessary by the framer.

In the Americas, two-bys (2×4s, 2×6s, 2×8s, 2×10s, and 2×12s) are common lumber sizes used in modern construction. They are the basic building block for such common structures as balloon-frame or platform-frame housing. Dimensional lumber made from softwood is typically used for construction, while hardwood boards are more commonly used for making cabinets or furniture.

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.

Hardwoods

Hardwood Dimensional Lumber Sizes
Nominal	Surfaced 1 Side (S1S)	Surfaced 2 sides (S2S)
⅜?	¼?	3/16?
½?	⅜?	5/16?
⅝?	½?	7/16?
¾?	⅝?	9/16?
1″ or 4/4	⅞?	13/16?
1¼″ or 5/4	1⅛?	1-1/16?
1½″ or 6/4	1⅜?	1-5/16?
2″ or 8/4	1-13/16?	1¾?
3″ or 12/4	2-13/16?	2¾?
4″ or 16/4	3-13/16?	3¾?

In North America sizes for dimensional lumber made from hardwoods varies from the sizes for softwoods. Boards are usually supplied in random widths and lengths of a specified thickness, and sold by the board-foot (144 cubic inches). This does not apply in all countries, for example in Australia many boards are sold to timber yards in packs with a common profile (dimensions) but not necessarily of consisting of the same length boards. Hardwoods cut for furniture are cut in the fall and winter, after the sap has stopped running in the trees. If hardwoods are cut in the spring or summer the sap ruins the natural color of the timber and deteriorates the value of the timber for furniture.

Also in North America hardwood lumber is commonly sold in a “quarter” system when referring to thickness. 4/4 (four quarters) refers to a one-inch thick board, 8/4 (eight quarters) is a two-inch thick board, etc. This system is not usually used for softwood lumber, although softwood decking is sometimes sold as 5/4 (actually one inch thick).

Engineered lumber

Engineered lumber is lumber created by a manufacturer and designed for a certain structural purpose. The main categories of engineered lumber are:^[1]

1. Laminated Veneer Lumber – Generally called "LVL", they come in 1-3/4″ thicknesses with depths such as 9″, 11-7/8″, 13″, 16″, 18″, 24″, and are typically doubled or tripled up. They function as beams to provide support over large spans such as removed support walls and garage door openings, places where dimensional lumber isn't structurally sound to use, and also in areas where a heavy load is bearing from a floor, wall or roof above on a somewhat short span where dimensional lumber isn't practical. This type of lumber cannot be altered by holes or notches anywhere within the span or at the ends as it compromises the integrity of the beam, but nails can be driven into it wherever necessary to anchor the beam or to add hangers for I-joists or dimensional lumber joists which terminate at an LVL.
2. Wood I-joists – Sometimes called "TJI" or "Trus Joists", which are both brands of wood I-joists, they are used for floor joists on upper floors and also in 1st floor conventional foundation construction on piers as opposed to slab floor construction. They are engineered for long spans and are doubled up in places where a wall will be placed over them, and sometimes tripled where heavy roof-loaded support walls are placed above them. They consist of a top and bottom chord/flange made from LVL with a webbing in-between made from OSB (oriented strand board). The webbing can be removed up to certain sizes/shapes according to the manufacturers (and engineers) specifications, but for small holes, wood I-joists come with "knockouts", which are perforated, pre-cut areas where holes can be made easily typically without engineering approval. When large holes are needed, they can typically be made in the webbing only (the top & bottom chords cannot be cut) and only in the center third of the span. Sizes & shapes of the hole, and typically the placing of a hole itself, must be approved by an engineer prior to the cutting of the hole and in many areas, a sheet showing the calculations made by the engineer must be provided to the building inspection authorities before the hole will be approved. Some I-joists are made with W-style webbing like a truss to eliminate cutting and allow ductwork to pass through.
   

   Freshly cut logs showing sap running from beneath bark
3. Finger-Jointed Lumber – Solid dimensional lumber lengths typically max out at lengths of 22′ to 24′, but is made longer by the technique of "finger-jointing" lumber by using small solid pieces, usually 18″ to 24″ long, and joining them together using finger-joints and glue to produce lengths that can be up to 36′ long in 2×6 size. Finger-jointing also is predominant in pre-cut wall studs.
4. Glu-lam Beams – Created by taking 2×4 or 2×6 stock and glueing the faces together to create beams such as 4×12 or 6×16. LVL beams have taken their place in most home construction.
5. Manufactured Trusses – Trusses are used in home construction as bracing to support the roof rafters in the attic space. It is seen as an easier installation and a better solution for supporting roofs as opposed to the use of dimensional lumber's struts & purlins as bracing. In the southern USA and other parts, stick-framing with dimensional lumber roof support is still predominant. The main drawback of trusses is that less attic space is usable.
6. Oriented Strand Board – OSB is made by adhering strands of wood in a certain direction and apply glue to make the piece strong for structural purposes. OSB has replaced plywood for use as exterior wall sheathing & roof decking (both in 7/16″ thickness minimum) and in 2nd story flooring in 3/4″ thickness in a tongue-and-groove interlocking pattern, which is nailed and glued to the I-joists. OSB used in wall sheathing & roof decking will swell up if exposed to the elements for even a brief period of time and must be replaced, therefore it is covered by a weatherproof membrane such as felt to protect it, secured with plastic cap nails. House wrapping is used on areas which will be sheathed with vinyl siding. 3/4″ T&G OSB flooring has a coating on it to protect it from the elements for a short period of time until the home is "dried-in" with a roof.

Defects in lumber

Defects occurring in timber are grouped into the following five divisions:

1. Defects due to conversion
2. Defects due to fungi
3. Defects due to insects
4. Defects due to natural forces
5. Defects due to seasoning

Preservatives

Main article: timber treatment

Timber or lumber may be treated with a preservative that protects it from being destroyed by insects, fungus or exposure to moisture. Generally this is applied through combined vacuum and pressure treatment. The preservatives used to pressure-treat lumber are classified as pesticides; due to potential hazards to humans and the environment, some are being phased out. Treating lumber provides long-term resistance to organisms that cause deterioration. If it is applied correctly, it extends the productive life of lumber by five to ten times. If left untreated, wood that is exposed to moisture or soil for sustained periods of time will become weakened by various types of fungi, bacteria or insects.

Timber framing

Main article: timber framing

Timber framing is a style of construction which uses heavier framing elements than modern stick framing, which uses dimensional lumber. The timbers originally were tree boles squared with a broadaxe or adze and joined together with joinery without nails. A modern imitation with sawn timbers is growing in popularity in the United States.

Miscellaneous

• The term TIMBER! is used as a warning call to alert others working in the area that a tree is being felled and that they should take care to be out of the way.
• The term "sending up timber" is used in some religious circles to signify sending up prayer and/or sacrifice to God.

See also

• British timber trade
• Deck (building)
• Forestry
• Hardwood Timber Production
• Illegal logging
• List of Indian timber trees
• List of woods
• Log Scaler
• Logging
• Non-timber forest products
• Plank
• Recycling timber
• Sawmill
• Sodium silicate's use as a timber treatment
• Timber treatment
• United States-Canada softwood lumber dispute
• Wood
• Woody plant
• Woodworking

References

External links

• Timber Development Association of NSW - Australia
• CPSC Test coatings to reduce arsenic emissions from pressure treated wood
• TRADA: Timber Research And Development Association
• Wood themed links and activities
• The Forest Products Laboratory. US main wood products research lab. Madison, WI (E)
• International Wood Collectors Society
• Xiloteca Manuel Soler (One of the largest private collection of wood samples)
• Humanitarian Timber project (A project to produce and disseminate a field handbook that brings together best practice in the procurement and use of timber in humanitarian emergencies)