Timber in storage for later processing
at a sawmill
Wood cut from Victorian Mountain
Ash
Lumber or
timber is
wood that is used in any of its stages from
felling through readiness for use as structural
material for
construction, or
wood
pulp for
paper production. (The
distinction between the two terms is discussed
below.)
Lumber is supplied either rough or finished. Besides
pulpwood,
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, primarily
softwood
from
coniferous species including
pine,
fir and
spruce (collectively known as
Spruce-pine-fir),
cedar,
hemlock, but also some
hardwood, for high-grade flooring.
Terminology
In the
United
Kingdom
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,
timber often refers to the wood
contents of standing, live trees that can be used for lumber or
fibre production, although it can also be used to describe sawn
lumber whose smallest dimension is not less than 5 inches (127
mm).
Note that the word
lumberjack is used in
the UK and Australia to refer to North Americans who fell standing
trees, and so the word "lumber" conjures images of what North
Americans call "timber", and vice versa.
"
Timber!" is also an interjection that lumberjacks
often shout out to warn others that a cut tree is about to
fall.
Dimensional lumber
Example of 2×4.
Dimensional lumber is a term used for lumber that
is finished/planed and cut to standardized width and depth
specified in
inches. Examples of common sizes
are
2×4 (
pictured, also
two-by-four and other variants, such as
four-by-two in the UK, Australia, New Zealand),
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.
North American softwood
dimensional lumber sizes
| Nominal |
Actual |
|
Nominal |
Actual |
|
Nominal |
Actual |
| 1 × 2 |
in × in (19 mm × 38 mm) |
|
2 × 2 |
in × in (38 mm × 38 mm) |
|
4 × 4 |
in × in (89 mm × 89 mm) |
| 1 × 3 |
in × in (19 mm × 64 mm) |
|
2 × 3 |
in × in (38 mm × 64 mm) |
|
4 × 6 |
in × in (89 mm × 140 mm) |
| 1 × 4 |
in × in (19 mm × 89 mm) |
|
2 × 4 |
in × in (38 mm × 89 mm) |
|
6 × 6 |
in × in (140 mm × 140 mm) |
| 1 × 6 |
in × in (19 mm × 140 mm) |
|
2 × 6 |
in × in (38 mm × 140 mm) |
|
8 × 8 |
in × in (184 mm × 184 mm) |
| 1 × 8 |
in × in (19 mm × 184 mm) |
|
2 × 8 |
in × in (38 mm × 184 mm) |
|
|
|
| 1 × 10 |
in × in (19 mm × 235 mm) |
|
2 × 10 |
in × in (38 mm × 235 mm) |
|
|
|
| 1 × 12 |
in × in (19 mm × 286 mm) |
|
2 × 12 |
in × in (38 mm × 286 mm) |
|
|
|
|
Note:
Treated 8x8
SYP pilings are
actually 8" x 8"
Solid dimensional lumber typically is only available up to lengths
of 24 ft, 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 ft
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
ft, 9 ft & 10 ft 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), along with the 4×4, 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.
For convenience, we refer to lumber by its nominal dimensions,
which are larger than its actual fractional size (see above table).
This difference occurs because
nominal dimensions
traditionally referred to
rough lumber,
whose size was reduced in drying and planing. In addition, the
standard finished dimensions of lumber have decreased through
time—the typical 13/16 inches for a 1-inch board in the 1910s was
reduced by 4% in 1929 and by another 4% in 1956, resulting in the
current standard of 3/4 inch. The move to set national standards
for lumber in the United States began with publication of the
American Lumber Standard in 1924, which set specifications for
lumber dimensions, grade, and moisture content; it also developed
inspection and accreditation programs. These standards have changed
over the years to meet the changing needs of consumers,
manufacturers, and distributors, so that lumber would remain
competitive with alternative construction products. Current
standards are set by the American Lumber Standard Committee,
appointed by the
Secretary of
Commerce.
Attempts to maintain lumber quality over time have been challenged
by historical changes in the timber resources of the United
States—from the slow-growing
virgin
forests common over a century ago to the fast-growing
plantation now common in today's
commercial forests. Resulting declines in lumber quality have
shifted use to alternative construction products and have been of
recent concern to both the lumber industry and consumers.
Hardwood dimensional lumber sizes
| Nominal |
Surfaced 1 Side (S1S) |
Surfaced 2 sides (S2S) |
| in |
in |
in |
| in |
in |
in |
| in |
in |
in |
| 1 in or in |
in |
in |
| in or in |
in |
in |
| in or in |
in |
in |
| 2 in or in |
in |
in |
| 3 in or in |
in |
in |
| 4 in or in |
in |
in |
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, th of a
cubic foot). 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:
- Laminated Veneer Lumber
– LVL comes in inch thicknesses with depths such as , , 14, 16, 18,
or 24 inches, and are often 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 sufficient, 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 that terminate at an LVL beam.
- Wood I-joists – Sometimes called "TJI","Trus Joists" or "BCI",
all of which are brands of wood I-joists, they are used for floor
joists on upper floors and also in first 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 aligned 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
dimensional lumber with a webbing in-between made from oriented
strand board (OSB). The webbing can be removed up to certain
sizes/shapes according to the manufacturer's or engineer's
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
and only in the center third of the span; the top and bottom chords
cannot be cut. Sizes and 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
- Finger-Jointed Lumber – Solid
dimensional lumber lengths typically are limited to lengths of 22
to 24 feet, but can be made longer by the technique of
"finger-jointing" lumber by using small solid pieces, usually 18 to
24 inches long, and joining them together using finger joints and
glue to produce lengths that can be up to 36 feet long in 2×6 size.
Finger-jointing also is predominant in precut wall studs. It is
also an affordable alternative for non-structural hardwood that
will be painted (staining would leave the finger-joints
visible).
- Glu-lam Beams – Created
from 2×4 or 2×6 stock by gluing the faces together to create beams
such as 4×12 or 6×16. By gluing multiple, common sized pieces of
lumber together, they act as one larger piece of lumber - thus
eliminating the need to harvest larger, older trees for the same
size beam.
- Manufactured Trusses – Trusses are used in
home construction as a pre-fabricated replacement for roof rafters
and ceiling joists (stick-framing). It is seen as an easier
installation and a better solution for supporting roofs as opposed
to the use of dimensional lumber's struts and 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 are reduced attic space, time required for engineering and
ordering, and a cost higher than the dimensional lumber needed if
the same project were conventionally framed. The advantages are
significantly reduced labor costs (installation is faster than
conventional framing), consistency, and overall schedule
savings.
Defects in lumber
Defects occurring in Timber are grouped into the following
five divisions:
Defects due to conversion
During the process of converting timber to commercial form, the
following defects may occur:
- Chip mark
- Diagonal grain
- Torn grain
- Wane
Defects due to fungi
Fungi attacks timber when these conditions
are all present:
- The timber moisture content is above 20%
- The environment is warm enough
- There is air
Wood with less than 20% moisture remains free of fungi for
centuries. Similarly, wood submerged in water will not be attacked
by fungi because of absence of air.
Fungi timber defects:
- Blue stain
- Brown rot
- Dry rot
- Heart rot
- Sap stain
- Wet rot
- White rot
Defects due to insects
Following are the insects which are usually responsible for the
decay of timber:
- Beetles
- Marine Borers
- Termites
- Red Ants
Defects due to natural forces
There are two main natural forces responsible for causing defects
in timber:
abnormal growth and
rupture of
tissues.
Defects due to seasoning
Defects due to seasoning are the number one cause for splinters and
slivers.
Preservatives
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. Many newer
preservatives are free of metallic compounds altogether, and are
instead based on biodegradable organic chemistry. 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
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.
One of the most conventional framing methods is the
Neumann
Notch, which involves a thirty-two degree angling of adjoining
lumber and then a right-angled wedge with an eighteen degree cusp
fitted between the lumber before being bolted. This convention was
pioneered by Daniel R. Neumann, a carpenter from Germany, that was
responsible for the structural development of the Massachusetts Bay
Colony in 1630. This framing convention spread to construction
sites in other colonies, most famously Plymouth and Concord.
Neumann's notched framing then was adopted by carpenters and
construction companies and this framing convention is still used
today in traditional frame sets.
Another somewhat less conventional method for framing is known as
the "New-style" binding. The basic setup of the New-style binding
was developed by Austin D. New, a Mormon settler in Salt Lake City,
Utah during the 1800s. The basic structure of the New-style binding
involves a set-up of two similar sized logs set against each other
perpendicularly and lashed together with hemp rope. This technique
was used to construct many of the early houses of the Mormon
settlers due to its ease of use and durability. Eventually the
New-style binding became obsolete as the settlers began
constructing homes out of the more traditional brick and
mortar.
Residual Wood
The conversion from coal to
biomass power is
a growing trend in the United States .
A
coal-fired power plant in Pepeekeo, Hawaii
that formerly provided electricity to a sugar mill is now being converted into a
24-megawatt (MW) biomass power plant. MMA Renewable Ventures is financing
the conversion and will operate the new plant, which will be called
the
Hū Honua Bioenergy
Facility .
Located about 8 miles north of Hilo
on the
Big Island of
Hawaii
, the facility will draw on residual wood from the local timber industry and other biomass wastes to produce
enough power for about 18,000 homes, meeting up to 10% of the Big
Island's electricity needs.
Remanufactured Lumber
Remanufactured Lumber refers to secondary or tertiary
processing/cutting of previously milled lumber. The term
specifically refers to lumber cut for industrial or
wood packaging use. Lumber is cut by ripsaw
or
resaw to create dimensions that are not
usually processed by a primary
sawmill.
Resawing is the process of splitting 1 inch through 12 inch
hardwood or
softwood lumber into two or more thinner pieces of
full length boards. For example, splitting a ten foot 2x4 into two
ten foot 1x4s is considered resawing.
In addition to resawing lumber, remanufactured lumber can be
ripped on a ripsaw using single or multiple blades.
Ripping is the process of splitting 1" through 12"
hardwood or
softwood lumber
into two or more narrower pieces of full length boards. For
example, splitting a ten foot 2x4 into two ten foot 2x2s is
considered ripping.
See also
References
- Smith, L.W. and L.W. Wood. 1964. History of yard lumber
size standards. USDA Forest Service, Forest Product
Laboratory.
- American Lumber Standard Committee: History.
- Nebraska Energy Office. Factsheet: Minimizing the
use of lumber products in residential construction.
- University of Washington, School of Forest
Resources. Material substitution in the U.S. residential
construction industry.
- http://www.eere.energy.gov/news/enn.cfm#id_11950
- http://www.mmarenewableventures.com/news/docs/hu_honua.pdf
- http://www.huhonua.com/proj_over.htm
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