is a sheet material manufactured from thin layers or "plies"
of wood veneer that are glued together with adjacent layers having
their wood grain rotated up to 90 degrees to one another. It is an
engineered wood from the family of manufactured boards which includes
medium-density fibreboard (MDF) and particle board (chipboard).
All plywoods bind resin and wood fibre sheets (cellulose cells are
long, strong and thin) to form a composite material. This alternation
of the grain is called cross-graining and has several important
benefits: it reduces the tendency of wood to split when nailed in at
the edges; it reduces expansion and shrinkage, providing improved
dimensional stability; and it makes the strength of the panel
consistent across all directions. There is usually an odd number of
plies, so that the sheet is balanced—this reduces warping. Because
plywood is bonded with grains running against one another and with an
odd number of composite parts, it has high stiffness perpendicular to
the grain direction of the surface ply.
Smaller, thinner, and lower quality plywoods may only have their plies
(layers) arranged at right angles to each other. Some better quality
plywood products will by design have five plies in steps of 45 degrees
(0, 45, 90, 135, and 180 degrees), giving strength in multiple axes.
3 Structural characteristics
4.4 Aircraft plywood
4.5 Decorative plywood (overlaid plywood)
4.6 Flexible plywood
4.7 Marine plywood
4.8 Other plywoods
Softwood plywood applications
Hardwood plywood applications
Tropical plywood applications
10 External links
The word "Ply" derives from the French verb plier, "to fold", from
the Latin verb plico, from the ancient Greek verb πλέκω.
Samuel Bentham applied for patents covering several machines
to produce veneers. In his patent applications, he described the
concept of laminating several layers of veneer with glue to form a
thicker piece – the first description of what we now call
plywood. Bentham was a British naval engineer with many
shipbuilding inventions to his credit. Veneers at the time of Bentham
were flat sawn, rift sawn or quarter sawn; i.e. cut along or across
the log manually in different angles to the grain and thus limited in
width and length.
About fifty years later Immanuel Nobel, father of Alfred Nobel,
realized that several thinner layers of wood bonded together would be
stronger than one single thick layer of wood understanding the
industrial potential of laminated wood he invented the rotary lathe.
There is little record of the early implementation of the rotary lathe
and the subsequent commercialization of plywood as we know it today,
but in its 1870 edition, the French dictionary Robert describes the
process of rotary lathe veneer manufacturing in its entry
Déroulage. One can thus presume that rotary lathe plywood
manufacture was an established process in France in the 1860s. Plywood
was introduced into the United States in 1865 and industrial
production started shortly after. In 1928, the first standard-sized
4 ft by 8 ft (1.2 m by 2.4 m) plywood sheets were introduced
in the United States for use as a general building material.
Artists use plywood as a support for easel paintings to replace
traditional canvas or cardboard. Ready-made artist boards for oil
painting in three-layered plywood (3-ply) were produced and sold in
New York as early as 1880.
In India, plywood is more commonly called "Kitply" after a leading
brand which pioneered the concept of waterproof plywood in the early
A typical plywood panel has face veneers of a higher grade than the
core veneers. The principal function of the core layers is to increase
the separation between the outer layers where the bending stresses are
highest, thus increasing the panel's resistance to bending. As a
result, thicker panels can span greater distances under the same
loads. In bending, the maximum stress occurs in the outermost layers,
one in tension, the other in compression.
Bending stress decreases
from the maximum at the face layers to nearly zero at the central
layer. Shear stress, by contrast, is higher in the center of the
panel, and at the outer fibres.
Average-quality plywood with 'show veneer'
High-quality concrete pouring plate in plywood
Different varieties of plywood exist for different applications:
Softwood plywood is usually made either of cedar,
Douglas fir or
spruce, pine, and fir (collectively known as spruce-pine-fir or SPF)
or redwood and is typically used for construction and industrial
The most common dimension is 1.2 by 2.4 metres (3 ft 11 in
× 7 ft 10 in) or the slightly larger imperial
dimension of 4 feet × 8 feet. Plies vary in thickness from
1.4 mm to 4.3 mm. The number of plies—which is always
odd—depends on the thickness and grade of the sheet. Roofing can use
the thinner 5/8" (15 mm) plywood. Subfloors are at least 3/4"
(18 mm) thick, the thickness depending on the distance between
Plywood for flooring applications is often tongue and
groove; This prevents one board from moving up or down relative to its
neighbor, providing a solid-feeling floor when the joints do not lie
over joists. T&G plywood is usually found in the 1/2" to 1"
(12–25 mm) range.
Hardwood plywood is made out of wood from angiosperm trees and used
for demanding end uses.
Hardwood plywood is characterized by its
excellent strength, stiffness and resistance to creep. It has a high
planar shear strength and impact resistance, which make it especially
suitable for heavy-duty floor and wall structures. Oriented plywood
construction has a high wheel-carrying capacity.
Hardwood plywood has
excellent surface hardness, and damage- and wear-resistance.
Tropical plywood is made of mixed species of tropical wood. Originally
from the Asian region, it is now also manufactured in African and
South American countries.
Tropical plywood is superior to softwood
plywood due to its density, strength, evenness of layers, and high
quality. It is usually sold at a premium in many markets if
manufactured with high standards.
Tropical plywood is widely used in
the UK, Japan, United States, Taiwan, Korea, Dubai, and other
countries worldwide. It is an excellent choice for construction
purposes[according to whom?] in many regions due to its low cost.
However, many countries’ forests have been over-harvested, including
Malaysia and Indonesia, largely due to the demand for
plywood production and export.
De Havilland DH-98 Mosquito was made of curved and glued veneers
High-strength plywood, also known as aircraft plywood, is made from
mahogany, spruce and/or birch using adhesives with an increased
resistance to heat and humidity. It was used in the construction of
air assault gliders during
World War II
World War II and also several fighter
aircraft, most notably the multi-role British Mosquito. Nicknamed "The
Wooden Wonder" plywood was used for the wing surfaces, and also flat
sections such as bulkheads and the webs of the wing spars. The
fuselage had exceptional rigidity from the bonded ply-balsa-ply
‘sandwich’ of its monocoque shell; elliptical in cross-section, it
was formed in two separate mirror-image halves, using curved moulds.
Structural aircraft-grade plywood is most commonly manufactured from
African mahogany, spruce or birch veneers that are bonded together in
a hot press over hardwood cores of basswood or poplar or from European
Birch veneers throughout. Basswood is another type of aviation-grade
plywood that is lighter and more flexible than mahogany and birch
plywood but has slightly less structural strength.
Aviation-grade plywood is manufactured to a number of specifications
including those outlined since 1931 in the Germanischer Lloyd Rules
for Surveying and Testing of
Plywood for Aircraft and MIL-P-607, the
latter of which calls for shear testing after immersion in boiling
water for three hours to verify the adhesive qualities between the
plies and meets specifications.
Decorative plywood (overlaid plywood)
Usually faced with hardwood, including ash, oak, red oak, birch,
maple, mahogany, Philippine mahogany (often called lauan, luan or
meranti and having no relation to true mahogany), rosewood, teak and a
large number of other hardwoods.
Flexible plywood is designed for making curved parts, a practice which
dates back to the 1850s in furniture making.
Aircraft grade plywood, often Baltic birch, is made from 3 or more
plies of birch, as thin as 1/64" thick in total, and is extremely
strong and light. At 3/8" thick, mahogany 3-ply "wiggle Board" or
"Bendy Board" come in 4' x 8' sheets with a very thin cross grain
central ply and two thicker exterior plies, either long grain on the
sheet, or cross grain. Wiggle board is often glued together in two
layers once it is formed into the desired curve, so that the final
shape will be stiff and resist movement. Often, decorative wood
veneers are added as a surface layer.
In the UK single ply sheets of veneer were used to make stovepipe hats
in Victorian times, so flexible modern plywood is sometimes known
there as "Hatters Ply", although the original
material was not strictly plywood, but a single sheet of veneer.
Marine plywood is manufactured from durable face and core veneers,
with few defects so it performs longer in both humid and wet
conditions and resists delaminating and fungal attack. Its
construction is such that it can be used in environments where it is
exposed to moisture for long periods. Each wood veneer will be from
tropical hardwoods, have negligible core gap, limiting the chance of
trapping water in the plywood and hence providing a solid and stable
glue bond. It uses an exterior Water and Boil Proof (WBP) glue similar
to most exterior plywoods.
Marine plywood can be graded as being compliant with BS 1088, which is
British Standard for marine plywood. There are few international
standards for grading marine plywood and most of the standards are
voluntary. Some marine plywood has a
Lloyd's of London
Lloyd's of London stamp that
certifies it to be
BS 1088 compliant. Some plywood is also labeled
based on the wood used to manufacture it. Examples of this are Okoumé
Other types of plywoods include fire-retardant, moisture-resistant,
wire mesh, sign-grade, and pressure-treated. However, the plywood may
be treated with various chemicals to improve the plywood's
fireproofing. Each of these products is designed to fill a need in
Birch plywood is a product of an area around the Baltic Sea.
Originally manufactured for European cabinet makers but now popular in
the United States as well. It is very stable composed of an inner
void-free core of cross-banded birch plys with an exterior grade
adhesive. The face veneers are thicker than traditional cabinet grade
Logs for plywood construction in a plywood factory
Plywood production requires a good log, called a peeler, which is
generally straighter and larger in diameter than one required for
processing into dimensioned lumber by a sawmill. The log is laid
horizontally and rotated about its long axis while a long blade is
pressed into it, causing a thin layer of wood to peel off (much as a
continuous sheet of paper from a roll). An adjustable nosebar, which
may be solid or a roller, is pressed against the log during rotation,
to create a "gap" for veneer to pass through between the knife and the
nosebar. The nosebar partly compresses the wood as it is peeled; it
controls vibration of the peeling knife; and assists in keeping the
veneer being peeled to an accurate thickness. In this way the log is
peeled into sheets of veneer, which are then cut to the desired
oversize dimensions, to allow it to shrink (depending on wood species)
when dried. The sheets are then patched, graded, glued together and
then baked in a press at a temperature of at least 140 °C
(284 °F), and at a pressure of up to 1.9 MPa (280 psi)
(but more commonly 200 psi) to form the plywood panel. The panel can
then be patched, have minor surface defects such as splits or small
knot holes filled, re-sized, sanded or otherwise refinished, depending
on the market for which it is intended.
Plywood for indoor use generally uses the less expensive
urea-formaldehyde glue, which has limited water resistance, while
outdoor and marine-grade plywood are designed to withstand moisture,
and use a water-resistant phenol-formaldehyde glue to prevent
delamination and to retain strength in high humidity.
Anti-fungal additives such as Xyligen (Furmecyclox) may sometimes
be added to the glueline to provide added resistance to fungal attack.
The adhesives used in plywood have become a point of concern. Both
urea formaldehyde and phenol formaldehyde are carcinogenic in very
high concentrations. As a result, many manufacturers are turning to
low formaldehyde-emitting glue systems, denoted by an "E" rating.
Plywood produced to "E0" has effectively zero formaldehyde
In addition to the glues being brought to the forefront, the wood
resources themselves are becoming the focus of manufacturers, due in
part to energy conservation, as well as concern for natural resources.
There are several certifications available to manufacturers who
participate in these programs. Programme for the Endorsement of Forest
Forest Stewardship Council
Forest Stewardship Council (FSC), Leadership in
Energy and Environmental Design (LEED), Sustainable Forestry
Initiative (SFI), and Greenguard are all certification programs that
ensure that production and construction practices are sustainable.
Many of these programs offer tax benefits to both the manufacturer and
the end user.
The most commonly used thickness range is from 1⁄8 to 3.0 inches
(3.2 to 76.2 mm). The sizes of the most commonly used plywood
sheets are 4 x 8 feet (1220 x 2440 mm) which was first used by
the Portland Manufacturing Company, who developed what we know of as
modern veneer core plywood for the 1905 Portland World Fair. A common
metric size for a sheet of plywood is 1200 x 2400 mm.
5 × 5 feet (1,500 × 1,500 mm) is also a
common European size for Baltic birch ply, and aircraft ply.
Sizes on specialised plywood for concrete-forming can range from
15⁄64 to 13⁄16 in (6 to 21 mm), and a multitude of
formats exist, though 15 × 750 × 1,500 mm
(.059 inch × 30 × 59 in)
(19/32in × 2 ft-6in × 4 ft-11in) is
very commonly used.
Aircraft plywood is available in thicknesses of 1⁄8 inch (3 mm)
(3 ply construction) and upwards; typically aircraft plywood uses
veneers of 0.5 mm (approx 1/64 in) thickness
although much thinner veneers such as 0.1 mm are also used in
construction of some of the thinner panels.
Grading rules differ according to the country of origin. The most
popular standards are the
British Standard (BS) and the American
Standard (ASTM). Joyce (1970), however, list some general indication
of grading rules:
Face and back veneers practically free from all defects.
Face veneers practically free from all defects. Reverse veneers with
only a few small knots or discolorations.
Face as A but reverse side permitting jointed veneers, large knots,
Both side veneers with only a few small knots or discolorations.
Face veneers with only a few small knots or discolorations. Reverse
side permitting jointed veneers, large knots, plugs, etc.
Both sides permitting jointed veneers, large knots, plugs, etc.
For structural plywood, this grade means that the face has knots and
defects filled in and the reverse may have some that are not filled.
Neither face is an appearance grade, nor are they sanded smooth. This
grade is often used for sheathing the surfaces of a building prior to
being covered with another product like flooring, siding, concrete, or
Guaranteed well glued only. All broken knots plugged.
Knots, knotholes, cracks, and all other defects permitted.
Weather and Boil Proof used in Marine Ply. Designation replaced by EN
Face as BB, back as CC. BB as very little knots of less than
1/4 inches, slight discoloration, no decay, split and wormholes
mended skillfully, matched colors, no blister, no wrinkle. Most
popular choice for most applications.
Plywood is used in many applications that need high-quality,
high-strength sheet material. Quality in this context means resistance
to cracking, breaking, shrinkage, twisting and warping.
Exterior glued plywood is suitable for outdoor use, but because
moisture affects the strength of wood, optimal performance is achieved
where the moisture content remains relatively low. Subzero conditions
do not affect the dimensional or strength properties of plywood,
making some special applications possible.
Plywood is also used as an engineering material for stressed-skin
applications. It has been used for marine and aviation applications
since WWII. Most notable is the British de Havilland Mosquito bomber,
with a fuselage made of birch plywood sandwiching a balsa core, and
using plywood extensively for the wings.
Plywood was also used for the
hulls in the hard-chine Motor Torpedo Boats (MTB) and Motor Gun Boats
(MGB) built by the
British Power Boat Company
British Power Boat Company and Vosper's.
currently successfully used in stressed-skin applications.[citation
needed] The American designers Charles and
Ray Eames are known for
their plywood-based furniture, as is Finnish Architect Alvar Aalto and
his firm Artek, while
Phil Bolger has designed a wide range of boats
built primarily of plywood. Jack Köper of Cape Town designed the
plywood Dabchick sailing dinghy, which as of 2015[update] is still
sailed by large numbers of teenagers.
Plywood is often used to create curved surfaces because it can easily
bend with the grain. Skateboard ramps often utilize plywood as the top
smooth surface over bent curves to create transition that can simulate
the shapes of ocean waves.
Softwood plywood applications
Typical end uses of spruce plywood are:
Floors, walls and roofs in home constructions
Wind bracing panels
Vehicle internal body work
Packages and boxes
There are coating solutions available that mask the prominent grain
structure of spruce plywood. For these coated plywoods there are some
end uses where reasonable strength is needed but the lightness of
spruce is a benefit e.g.:
Concrete shuttering panels
Ready-to-paint surfaces for constructions
Hardwood plywood applications
Phenolic resin film coated (Film Faced) plywood is typically used as a
ready-to-install component e.g.:
Panels in concrete form work systems
Floors, walls and roofs in transport vehicles
Floors subjected to heavy wear in various buildings and factories
("Wire" or other styles of imprinting available for better traction)
Birch plywood is used as a structural material in special applications
Wind turbine blades
Insulation boxes for liquefied natural gas (LNG) carriers
Smooth surface and accurate thickness combined with the durability of
the material makes birch plywood a favorable material for many special
end uses e.g.:
High-end loud speakers
Supporting structure for parquet
Signs and fences for demanding outdoor advertising
Tropical plywood applications
Tropical plywood is widely available from the South-East Asia region,
Malaysia and Indonesia.
Tropical plywood boasts premium
quality, and strength. Depending on machinery, tropical plywood can be
made with high accuracy in thickness, and is a highly preferable
choice in America, Japan, Middle East, Korea, and other regions around
Laminated veneer lumber
Laminated veneer lumber (LVL)
^ Collins Dictionary of the English Language, 2nd Edition, London,
^ Cassell's Latin Dictionary, Marchant, J.R.V, & Charles, Joseph
F., (Eds.), Revised Edition, 1928, p.421
^ a b "Plywood". Gale's How Products are Made. The Gale Group Inc.
Retrieved 26 November 2013.
^ "Nobel Plywood". Retrieved 2018-04-03.
^ "Dérouler". Le Robert Historique de la langue française.
Dictionnaires Robert. Retrieved 26 November 2013.
^ "Plywood". Columbia Encyclopedia. Retrieved 26 November 2013.
^ Muller, Norman E. "An early example of a plywood support for
painting". Journal of the American Institute for Conservation.
American Institute for Conservation of Historic and Artistic Works.
Retrieved 26 November 2013.
^ O'Halloran, p. 221.
^ Handbook of Finnish plywood, Finnish Forest Industries Federation,
2002, ISBN 952-9506-63-5 "Archived copy" (PDF). Archived from the
original (PDF) on 2007-09-27. Retrieved 2007-09-27.
^ Entry on the PAN Pesticide Database. Retrieved 8 June 2016.
Wood Products Association of Australasia. (PDF).
Retrieved on 2012-02-10.
Woodworking Tips.com. Pro
Woodworking Tips.com. Retrieved on
^ Metric conversions, Canadian government publication Archived
2010-02-16 at the Wayback Machine.. (PDF). Retrieved on 2012-02-10.
^ Joyce, Ernes. 1970. The Technique of Furniture Making. London: B. T.
Look up plywood in Wiktionary, the free dictionary.
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