Composite wood
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Engineered wood, also called mass timber, composite wood, man-made wood, or manufactured board, includes a range of derivative
wood products Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin t ...
which are manufactured by binding or fixing the strands, particles, fibres, or veneers or boards of wood, together with
adhesive Adhesive, also known as glue, cement, mucilage, or paste, is any non-metallic substance applied to one or both surfaces of two separate items that binds them together and resists their separation. The use of adhesives offers certain advant ...
s, or other methods of fixation to form
composite material A composite material (also called a composition material or shortened to composite, which is the common name) is a material which is produced from two or more constituent materials. These constituent materials have notably dissimilar chemical or ...
. The panels vary in size but can range upwards of and in the case of
cross-laminated timber Cross-laminated timber (CLT) (a sub-category of engineered wood) is a wood panel product made from gluing together at least three layers of solid-sawn lumber, i.e., lumber cut from a single log. Each layer of boards is usually oriented perpendic ...
(CLT) can be of any thickness from a few inches to or more. These products are
engineered Engineering is the use of scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehicles, and buildings. The discipline of engineering encompasses a broad range of more speciali ...
to precise design specifications, which are tested to meet national or international standards and provide uniformity and predictability in their structural performance. Engineered wood products are used in a variety of applications, from home construction to commercial buildings to industrial products.A Guide To Engineered Wood Products, Form C800
Apawood.org. Retrieved on February 10, 2012.
The products can be used for joists and beams that replace steel in many building projects. The term ''mass timber'' describes a group of building materials that can replace concrete assemblies. Broad-base adoption of mass timber and their substitution for steel and concrete in new mid-rise construction projects over the coming decades could help mitigate climate change. Typically, engineered wood products are made from the same
hardwood Hardwood is wood from dicot trees. These are usually found in broad-leaved temperate and tropical forests. In temperate and boreal latitudes they are mostly deciduous, but in tropics and subtropics mostly evergreen. Hardwood (which comes from ...
s and
softwood Scots Pine, a typical and well-known softwood Softwood is wood from gymnosperm trees such as conifers. The term is opposed to hardwood, which is the wood from angiosperm trees. The main differences between hardwoods and softwoods is that the s ...
s used to manufacture
lumber Lumber is wood that has been processed into dimensional lumber, including beams and planks or boards, a stage in the process of wood production. Lumber is mainly used for construction framing, as well as finishing (floors, wall panels, w ...
.
Sawmill A sawmill (saw mill, saw-mill) or lumber mill is a facility where logging, logs are cut into lumber. Modern sawmills use a motorized saw to cut logs lengthwise to make long pieces, and crosswise to length depending on standard or custom sizes ...
scraps and other wood waste can be used for engineered wood composed of wood particles or fibers, but whole logs are usually used for veneers, such as
plywood Plywood is a 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 ...
,
medium-density fibreboard Medium-density fibreboard (MDF) is an engineered wood product made by breaking down hardwood or softwood residuals into wood fibres, often in a defibrator, combining it with wax and a resin binder, and forming it into panels by applying high t ...
(MDF), or
particle board Particle board, also known as chipboard or low-density fiberboard, is an engineered wood product manufactured from wood chips and a synthetic resin or other suitable binder, which is pressed and extruded. Particle board is often confused with ...
. Some engineered wood products, like oriented strand board (OSB), can use trees from the poplar family, a common but non-structural species. Alternatively, it is also possible to manufacture similar
engineered bamboo Engineered bamboo is a set of composite products produced from bamboo. It is designed to be a replacement for wood or engineered wood, but is used only when high load bearing strength is not required because building standards for this type of use h ...
from bamboo; and similar engineered cellulosic products from other
lignin Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidity a ...
-containing materials such as rye straw,
wheat Wheat is a grass widely cultivated for its seed, a cereal grain that is a worldwide staple food. The many species of wheat together make up the genus ''Triticum'' ; the most widely grown is common wheat (''T. aestivum''). The archaeologi ...
straw,
rice Rice is the seed of the grass species '' Oryza sativa'' (Asian rice) or less commonly ''Oryza glaberrima'' (African rice). The name wild rice is usually used for species of the genera '' Zizania'' and '' Porteresia'', both wild and domesticat ...
straw,
hemp Hemp, or industrial hemp, is a botanical class of '' Cannabis sativa'' cultivars grown specifically for industrial or medicinal use. It can be used to make a wide range of products. Along with bamboo, hemp is among the fastest growing plants ...
stalks,
kenaf Kenaf tymology: Persian ''Hibiscus cannabinus'', is a plant in the family Malvaceae also called Deccan hemp and Java jute. ''Hibiscus cannabinus'' is in the genus '' Hibiscus'' and is native to Africa, though its exact origin is unknown. The name ...
stalks, or
sugar cane residue Bagasse ( ) is the dry pulpy fibrous material that remains after crushing sugarcane or sorghum stalks to extract their juice. It is used as a biofuel for the production of heat, energy, and electricity, and in the manufacture of pulp and building ...
, in which case they contain no actual wood but rather
vegetable fiber Fiber crops are field crops grown for their fibers, which are traditionally used to make paper, cloth, or rope. Fiber crops are characterized by having a large concentration of cellulose, which is what gives them their strength. The fibers may b ...
s. Flat-pack furniture is typically made out of man-made wood due to its low manufacturing costs and its low weight.


Types of products

There are a wide variety of engineered wood products for both structural and non-structural applications. This list is not comprehensive, and is intended to help categorize and distinguish between different types of engineered wood.


Wood-based panels

Wood structural panels are a collection of flat panel products, used extensively in building construction for sheathing, decking, cabinetry and millwork, and furniture. Examples include plywood and oriented strand board (OSB). Non-structural wood-based panels are flat-panel products, used in non-structural construction applications and furniture. Non-structural panels are usually covered with paint, wood veneer, or resin paper in their final form. Examples include fibreboard and particle board.


Plywood

Plywood Plywood is a 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 ...
, a wood structural panel, is sometimes called the original engineered wood product. Plywood is manufactured from sheets of cross-laminated veneer and bonded under heat and pressure with durable, moisture-resistant adhesives. By alternating the grain direction of the veneers from layer to layer, or "cross-orienting", panel strength and stiffness in both directions are maximized. Other structural wood panels include oriented strand boards and structural composite panels.APA A glossary of Engineered Wood Terms
. Apawood.org. Retrieved on February 10, 2012.


Oriented strand board

Oriented strand board (OSB) is a wood structural panel manufactured from rectangular-shaped strands of wood that are oriented lengthwise and then arranged in layers, laid up into mats, and bonded together with moisture-resistant, heat-cured adhesives. The individual layers can be cross-oriented to provide strength and stiffness to the panel. Similar to plywood, most OSB panels are delivered with more strength in one direction. The wood strands in the outermost layer on each side of the board are normally aligned into the strongest direction of the board. Arrows on the product will often identify the strongest direction of the board (the height, or longest dimension, in most cases). Produced in huge, continuous mats, OSB is a solid panel product of consistent quality with no laps, gaps, or voids. OSB is delivered in various dimensions, strengths, and levels of water resistance. OSB and plywood are often used interchangeably in building construction.


Fibreboard

Medium-density fibreboard Medium-density fibreboard (MDF) is an engineered wood product made by breaking down hardwood or softwood residuals into wood fibres, often in a defibrator, combining it with wax and a resin binder, and forming it into panels by applying high t ...
(MDF) and high-density fibreboard ( hardboard or HDF) are made by breaking down hardwood or softwood residuals into wood fibers, combining them with wax and a resin binder, and forming panels by applying high temperature and pressure.Corky Binggeli. (2013), "Materials for Interior Environments". MDF is used in non-structural applications.


Particle board

Particle board Particle board, also known as chipboard or low-density fiberboard, is an engineered wood product manufactured from wood chips and a synthetic resin or other suitable binder, which is pressed and extruded. Particle board is often confused with ...
is manufactured from wood chips, sawmill shavings, or even
sawdust Sawdust (or wood dust) is a by-product or waste product of woodworking operations such as sawing, sanding, milling, planing, and routing. It is composed of small chippings of wood. These operations can be performed by woodworking machine ...
, and a
synthetic resin Synthetic resins are industrially produced resins, typically viscous substances that convert into rigid polymers by the process of curing. In order to undergo curing, resins typically contain reactive end groups, such as acrylates or epoxides. ...
or another suitable binder, which is pressed and extruded. In recent time, research have shown that durable particle board can be produced from agricultural waste products, such as
rice husk Rice hulls (or rice husks) are the hard protecting coverings of grains of rice. In addition to protecting rice during the growing season, rice hulls can be put to use as building material, fertilizer, insulation material, or fuel. Rice hulls are ...
or guinea corn husk. Particleboard is cheaper, denser, and more uniform than conventional wood and plywood and is substituted for them when the cost is more important than strength and appearance. A major disadvantage of particleboard is that it is very prone to expansion and discoloration due to moisture, particularly when it is not covered with paint or another sealer. Particle board is used in non-structural applications.


Structural composite lumber

Structural composite lumber (SCL) is a class of materials made with layers of veneers, strands, or flakes bonded with adhesives. Unlike wood structural panels, structural composite lumber products generally have all grain fibers oriented in the same direction. The SCL family of engineered wood products are commonly used in the same structural applications as conventional sawn lumber and timber, including rafters, headers, beams, joists, rim boards, studs, and columns. SCL products have higher dimensional stability and increased strength compared to conventional lumber products.


Laminated veneer

Laminated veneer lumber Laminated veneer lumber (LVL) is an engineered wood product that uses multiple layers of thin wood assembled with adhesives. It is typically used for headers, beams, rimboard, and edge-forming material. LVL offers several advantages over typi ...
(LVL) is produced by bonding thin wood veneers together in a large billet, similar to plywood. The grain of all veneers in the LVL billet is parallel to the long direction (unlike plywood). The resulting product features enhanced mechanical properties and dimensional stability that offer a broader range in product width, depth, and length than conventional lumber.


Parallel strand

Parallel strand lumber Parallel-strand lumber (PSL) is a form of engineered wood made from parallel wood strands bonded together with adhesive. It is used for beams, headers, columns, and posts, among other uses. The strands in PSL are clipped veneer elements having a ...
(PSL) consists of long veneer strands laid in parallel formation and bonded together with an adhesive to form the finished structural section. The length-to-thickness ratio of strands in PSL is about 300. A strong, consistent material, it has a high load-carrying ability and is resistant to seasoning stresses so it is well suited for use as beams and columns for post and beam construction, and for beams, headers, and lintels for light framing construction.


Laminated strand

Laminated strand lumber (LSL) and oriented strand lumber (OSL) are manufactured from flaked wood strands that have a high length-to-thickness ratio. Combined with an adhesive, the strands are oriented and formed into a large mat or billet and pressed. LSL and OSL offer good fastener-holding strength and mechanical-connector performance and are commonly used in a variety of applications, such as beams, headers, studs, rim boards, and millwork components. LSL is manufactured from relatively short strands—typically about long—compared to the strands used in PSL. The length-to-thickness ratio of strands is about 150 for LSL and 75 for OSL.


I-joists

I-joists are ""-shaped structural members designed for use in floor and roof construction. An I-joist consists of top and bottom flanges of various widths united with webs of various depths. The flanges resist common bending stresses, and the web provides shear performance. I-joists are designed to carry heavy loads over long distances while using less lumber than a dimensional solid wood joist of a size necessary to do the same task. As of 2005, approximately half of all wood light framed floors were framed using I-joists.


Mass timber

Mass timber, also known as engineered timber, is a class of large structural wood components for building construction. Mass timber components are made of lumber or veneers bonded with adhesives or mechanical fasteners. Certain types of mass timber, such as nail-laminated timber and glue-laminated timber, have existed for over a hundred years. Mass timber has enjoyed increasing popularity in the past decade, due to growing concern around the sustainability of building materials, and interest in prefabrication, off site construction, and modularization, for which mass timber is well suited. The various types of mass timber share the advantage of faster construction times as the components are manufactured off-site, and pre-finished to exact dimensions for simple on-site fastening. Mass timber has been shown to have structural properties competitive with steel and concrete, opening the possibility to build large, tall buildings out of wood. Extensive testing has demonstrated the natural fire resistance properties of mass timber primarily due the creation of a char layer around a column or beam which prevents fire from reaching the inner layers of wood. In recognition of the proven structural and fire performance of mass timber, the International Building Code, a model code that forms the basis of many North American building codes, adopted new provisions in the 2021 code cycle that permit mass timber to be used in high-rise construction up to 18 stories.


Cross-laminated timber

Cross-laminated timber Cross-laminated timber (CLT) (a sub-category of engineered wood) is a wood panel product made from gluing together at least three layers of solid-sawn lumber, i.e., lumber cut from a single log. Each layer of boards is usually oriented perpendic ...
(CLT) is a versatile multi-layered panel made of lumber. Each layer of boards is placed perpendicular to adjacent layers for increased rigidity and strength.FPInnovations Cross-Laminated Timber: A Primer
(PDF) . Retrieved on February 10, 2012.
It is relatively new and gaining popularity within the construction industry as it can be used for long spans and all assemblies, e.g. floors, walls, or roofs.Abed, Joseph & Rayburg, Scott & Rodwell, John & Neave, Melissa. (2022). A Review of the Performance and Benefits of Mass Timber as an Alternative to Concrete and Steel for Improving the Sustainability of Structures. Sustainability. 14. 5570. 10.3390/su14095570.


Glue-laminated timber

Glue-laminated timber (glulam) is composed of several layers of dimensional timber glued together with moisture-resistant adhesives, creating a large, strong, structural member that can be used as vertical columns or horizontal beams. Glulam can also be produced in curved shapes, offering extensive design flexibility.


Dowel-laminated timber

Dowel laminated timber (DLT) is a less known type of mass timber product.  It is made by placing multiple boards of softwood lumber next to each together, each with a hole so that a hardwood dowel can be friction fitted through all of them.  As the hardwood dowel dries to reach an equilibrium moisture content with the softwood lumber, it expands into the surrounding boards creating a connection.  The use of a dowel connection eliminates the need for any metal fasteners or adhesives.


Nail-laminated timber

Nail laminated timber (NLT) is a mass timber product that consists of parallel boards fastened with nails. It can be used to create floors, roofs, walls, and elevator shafts within a building. It is one of the oldest types of mass timber, being used in warehouse construction during the
Industrial Revolution The Industrial Revolution was the transition to new manufacturing processes in Great Britain, continental Europe, and the United States, that occurred during the period from around 1760 to about 1820–1840. This transition included going f ...
. Like DLT, no chemical adhesives are used, and wood fibers are oriented in the same direction.


Structural composite lumber

Structural composite lumber (SCL) can be categorized into two different types of products:
laminated veneer lumber Laminated veneer lumber (LVL) is an engineered wood product that uses multiple layers of thin wood assembled with adhesives. It is typically used for headers, beams, rimboard, and edge-forming material. LVL offers several advantages over typi ...
(LVL) and laminated strand lumber (LSL).  SCL is created by gluing smaller pieces of wood together to create one solid structural member.  Of the two SCL products, LVLs are more common than LSLs.  While LVLs use wood veneers and LSLs use timber strands, they are both suited for residential construction and can be used as beams joists, studs, and rafters.


Engineered wood flooring

Engineered wood flooring is a type of flooring product, similar to hardwood flooring, made of layers of wood or wood-based composite laminated together. The floor boards are usually milled with a tongue-and-groove profile on the edges for consistent joinery between boards.


Lamella

The lamella is the face layer of the wood that is visible when installed. Typically, it is a sawn piece of timber. The timber can be cut in three different styles: flat-sawn, quarter-sawn, and rift-sawn.


Types of core/substrate

#Wood ply construction ("sandwich core"): Uses multiple thin plies of wood adhered together. The wood grain of each ply runs perpendicular to the ply below it. Stability is attained from using thin layers of wood that have little to no reaction to climatic change. The wood is further stabilized due to equal pressure being exerted lengthwise and widthwise from the plies running perpendicular to each other. #Finger core construction: Finger core engineered wood floors are made of small pieces of milled timber that run perpendicular to the top layer (lamella) of wood. They can be 2-ply or 3-ply, depending on their intended use. If it is three-ply, the third ply is often plywood that runs parallel to the lamella. Stability is gained through the grains running perpendicular to each other, and the expansion and contraction of wood are reduced and relegated to the middle ply, stopping the floor from gapping or cupping. #Fibreboard: The core is made up of medium or high-density fibreboard. Floors with a fibreboard core are hygroscopic and must never be exposed to large amounts of water or very high humidity - the expansion caused by absorbing water combined with the density of the fibreboard, will cause it to lose its form. Fibreboard is less expensive than timber and can emit higher levels of harmful gases due to its relatively high adhesive content. #An engineered flooring construction that is popular in parts of Europe is the hardwood lamella, softwood core laid perpendicular to the lamella, and a final backing layer of the same noble wood used for the lamella. Other noble hardwoods are sometimes used for the back layer but must be compatible. This is thought by many to be the most stable of engineered floors.


Other types of modified wood

New techniques have been introduced in the field of engineered wood in recent years. Natural wood is being transformed in laboratories through various chemical and physical treatments to achieve tailored mechanical, optical, thermal, and conduction properties, by influencing the wood’s structure.


Densified wood

Densified wood can be made by using a mechanical hot press to compress wood fibers, sometimes in combination with chemical modification of the wood. These processes have been shown to increase the density by a factor of three. This increase in density is expected to enhance the strength and stiffness of the wood by a proportional amount. More recent studies have combined chemical processes with traditional mechanical hot press methods. These chemical processes break down
lignin Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidity a ...
and
hemicellulose A hemicellulose (also known as polyose) is one of a number of heteropolymers (matrix polysaccharides), such as arabinoxylans, present along with cellulose in almost all terrestrial plant cell walls.Scheller HV, Ulvskov Hemicelluloses.// Annu Rev ...
that are found naturally in the wood. Following dissolution, the cellulose strands that remain are mechanically hot compressed. Compared to the three-fold increase in strength observed from hot pressing alone, chemically processed wood has been shown to yield an 11-fold improvement. This extra strength comes from
hydrogen bonds In chemistry, a hydrogen bond (or H-bond) is a primarily electrostatic force of attraction between a hydrogen (H) atom which is covalently bound to a more electronegative "donor" atom or group (Dn), and another electronegative atom bearing a l ...
formed between the aligned cellulose nanofibers. The densified wood possessed mechanical strength properties on par with steel used in building construction, opening the door for applications of densified wood in situations where regular strength wood would fail. Environmentally, wood requires significantly less carbon dioxide to produce than steel.


Thermally efficient wood

Removing
lignin Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidity a ...
from wood has several other applications, apart from providing structural advantages. Delignification alters the mechanical, thermal, optical, fluidic and ionic properties and functions of the natural wood and is an effective approach to regulating its thermal properties, as it removes the thermally conductive lignin component, while generating a large number of
nanopore A nanopore is a pore of nanometer size. It may, for example, be created by a pore-forming protein or as a hole in synthetic materials such as silicon or graphene. When a nanopore is present in an electrically insulating membrane, it can be used ...
s in the
cell wall A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane. It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a filtering mec ...
s which help reduce temperature change. Delignified wood reflects most incident light and appears white in color. White wood (also known as “nanowood”) has high reflection haze, as well as high
emissivity The emissivity of the surface of a material is its effectiveness in emitting energy as thermal radiation. Thermal radiation is electromagnetic radiation that most commonly includes both visible radiation (light) and infrared radiation, which is n ...
in the
infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of Light, visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from ...
wavelengths. These two characteristics generate a passive
radiative cooling In the study of heat transfer, radiative cooling is the process by which a body loses heat by thermal radiation. As Planck's law describes, every physical body spontaneously and continuously emits electromagnetic radiation. Radiative coolin ...
effect, with an average cooling power of over a 24-hour period, meaning that this wood does not "absorb" heat and therefore only emits the heat embedded in it. Moreover, white wood not only possesses a lower
thermal conductivity The thermal conductivity of a material is a measure of its ability to conduct heat. It is commonly denoted by k, \lambda, or \kappa. Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal ...
than natural wood, and it has better thermal performance than most commercially available insulating materials. The modification of the mesoporous structure of the wood is responsible for the changes in wood performance. White wood can also be put through a compression process, similar to the process mentioned for densified wood, which increases its mechanical performance compared to natural wood (8.7 times higher in tensile strength and 10 times higher in toughness). The thermal and structural advantages of nanowood make it an attractive material for energy-efficient building construction. However, the changes made in the wood’s structural properties, like the increase in structural porosity and the partially isolated
cellulose Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell wa ...
nanofibrils, damage the material’s mechanical robustness. To deal with this issue, several strategies have been proposed, with one being to further densify the structure, and another to use
cross-link In chemistry and biology a cross-link is a bond or a short sequence of bonds that links one polymer chain to another. These links may take the form of covalent bonds or ionic bonds and the polymers can be either synthetic polymers or natural ...
ing. Other suggestions include hybridizing natural wood with other organic particles and polymers to enhance its
thermal insulation Thermal insulation is the reduction of heat transfer (i.e., the transfer of thermal energy between objects of differing temperature) between objects in thermal contact or in range of radiative influence. Thermal insulation can be achieved with ...
performance.


Moldable wood

Using similar chemical modification techniques to chemically densified wood, wood can be made extremely moldable using a combination of delignification and water shock treatment. This is an emerging technology and is not yet used in industrial processes. However, initial tests show promising advantages in improved mechanical properties, with the molded wood exhibiting strength comparable to some metal alloys.


Transparent wood composites

Transparent wood composites are new materials, currently only made at the laboratory scale, that combines transparency and stiffness via a chemical process that replaces light-absorbing compounds, such as
lignin Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and bark, because they lend rigidity a ...
, with a transparent polymer.


Environmental benefits

With the global population growing at the rate, it is right now, there is going to be an enormous demand for new housing, commercial buildings, and infrastructure to sustain everyone.  The main materials used to build these buildings are steel and concrete, but they emit tons of
carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is t ...
() into the atmosphere which is not good for the environment.  A material that has the potential to reduce carbon emissions is engineered wood if it replaces steel concrete as the primary material in the construction of buildings. Not only do buildings made from engineered wood act as a
carbon sink A carbon sink is anything, natural or otherwise, that accumulates and stores some carbon-containing chemical compound for an indefinite period and thereby removes carbon dioxide () from the atmosphere. Globally, the two most important carbon si ...
, but they also produce less emissions in the manufacturing process than steel and cement, which both emit a lot of due to the chemical processes involved in their manufacturing. For example, in 2014, steel and cement production accounted for about 1320 megatonnnes (Mt) and 1740 Mt respectively, which made up about 9% of global emissions that year. In a study that did not take the
carbon sequestration Carbon sequestration is the process of storing carbon in a carbon pool. Carbon dioxide () is naturally captured from the atmosphere through biological, chemical, and physical processes. These changes can be accelerated through changes in lan ...
potential of engineered wood into account, it was found that roughly 50 Mt e (carbon dioxide equivalent) could be eliminated by 2050 with the full uptake of a hybrid construction system utilizing engineered wood and steel. When considering the added effects that carbon sequestration can have over the lifetime of the material, the emissions reductions of engineered wood is even more substantial, as laminated wood that is not incinerated at the end of its lifecycle absorbs around 582 kg of /m3, while reinforced concrete emits 458 kg /m3 and steel 12.087 kg /m3. There is not a strong consensus for measuring the carbon sequestration potential of wood. In life-cycle assessment, sequestered carbon is sometimes called biogenic carbon. ISO 21930, a standard that governs life cycle assessment, requires the biogenic carbon from a wood product can only be included as a negative input (i.e. carbon sequestration) when the wood product originated in a sustainably managed forest. This generally means that wood needs to be FSC or SFI-certified to qualify as carbon sequestering.


Advantages

Engineered wood products are used in a variety of ways, often in applications similar to solid wood products: * Mass timber (MT) is lightweight allowing the wood to be easily handled, manufactured, and transported. This contributes to it being cost effective and easy to use on site. * MT offers greater strength and stiffness (based on its strength to weight ratio), increased dimensional stability, and uniformity in structures. * When compared to steel/concrete, MT built buildings use up to 15% less energy because of the reduced energy needed to create these wood products. * MT buildings on average save 20-25% in time when compared to conventional steel/concrete buildings and 4.2% on capital cost. * MT products sequester carbon and store it within themselves over their lifespan.  Using this instead of concrete and steel in buildings will reduce the embodied emissions in buildings. * Using MT has an estimated savings of around 20% in embodied carbon when compared to steel or concrete.  This is because MT is a lot lighter when compared to these two materials, so it is less intensive for the machinery to transport both to site and once delivered. * MT products also have high levels of airtightness and low coefficients of thermal conductivity meaning that the air inside cannot escape, and heat isn’t lost easily. * MT built buildings perform very well in seismic events because they are roughly half the mass and half the stiffness when compared to reinforced concrete buildings which properties that are desirable.  Having half the stiffness allows MT buildings to be ductile which leads to it being able to resist lateral distortion without compromising the structural integrity of the building. * MT is fire resistant to an extent.  Although it is considered a combustible material, MT burns slow and in a predictable manner.  When it is burned, a charred layer is formed on the outside that protects the inner layers of the wood.  However, once the charred layer falls off, the inner layers will be exposed which can compromise the integrity of the material. All mass timber products offer different types of advantages, and they can be seen in the following: * CLT: Offers high dimensional stability, high strength and stiffness and is easy to manufacture. * Glulam: Offers high strength and stiffness, is structurally efficient, and can be manufactured into complex shapes. * NLT: Doesn’t require any specialized equipment to manufacture, is cost effective, and easy to handle. * DLT: Offers high dimensional stability, is easy and safe to manufacture, and no metal fasteners or adhesive is required. * SCL: Is able to withstand greater loads compared to solid timber and is not prone to shrinking, splitting or warping. Engineered wood products may be preferred over solid wood in some applications due to certain comparative advantages: * Because engineered wood is man-made, it can be designed to meet application-specific performance requirements. Required shapes and dimension do not drive source tree requirements (length or width of the tree) * Engineered wood products are versatile and available in a wide variety of thicknesses, sizes, grades, and exposure durability classifications, making the products ideal for use in unlimited construction, industrial, and home project application.Wood University
Wood University. Retrieved on February 10, 2012.
* Engineered wood products are designed and manufactured to maximize the natural strength and stiffness characteristics of wood. The products are very stable and some offer greater structural strength than typical wood building materials. *Glued laminated timber ( glulam) has greater strength and stiffness than comparable dimensional lumber and, pound for pound, is stronger than steel. * Engineered wood panels are easy to work with using ordinary tools and basic skills. They can be cut, drilled, routed, jointed, glued, and fastened. Plywood can be bent to form curved surfaces without loss of strength. Large panel sizes speeds up construction by reducing the number of pieces that need to be handled and installed. * Engineered wood products are a more efficient use of wood as they can be made from wood that has defects, underutilized species or smaller pieces of wood which also enables the use of smaller trees * Wooden trusses are competitive in many roof and floor applications, and their high strength-to-weight ratios permit long spans offering flexibility in floor layouts. *
Sustainable design Environmentally sustainable design (also called environmentally conscious design, eco-design, etc.) is the philosophy of designing physical objects, the built environment, and services to comply with the principles of ecological sustainability ...
advocates recommend using engineered wood, which can be produced from relatively small trees, rather than large pieces of solid
dimensional lumber Lumber is wood that has been processed into dimensional lumber, including beams and planks or boards, a stage in the process of wood production. Lumber is mainly used for construction framing, as well as finishing (floors, wall panels, w ...
, which requires cutting a large tree.Mary McLeod et al
"Guide to the single-family home rating"
. Austin Energy Green Building. HARSHITA p. 31-32.


Disadvantages

* Like solid wood, when exposed to high moisture conditions or termites, biodeteriorations and/or fungi decay will occur which reduces the structural integrity and durability of the wood product; essentially the wood will start to rot. * Raises concerns about potential widespread deforestation but can be mitigated with a sustainable forestry management plan. * MT buildings are susceptible to wind driven oscillation because of the relative flexibility of the MT material which may cause discomfort to people in the building. All mass timber products have different disadvantages, and they can be seen in the following: * CLT and Glulam: They both have high cost. * NLT: It is labor intensive to make and there is significant potential for human error. * DLT: It has limited panel sizing and thickness. * SCL: It has limited panel sizing and thickness and is more suitable for low rise buildings. When compared to solid wood the following disadvantages are prevalent: * They require more primary energy for their manufacture than solid lumber. * The
adhesive Adhesive, also known as glue, cement, mucilage, or paste, is any non-metallic substance applied to one or both surfaces of two separate items that binds them together and resists their separation. The use of adhesives offers certain advant ...
s used in some products may be toxic. A concern with some resins is the release of
formaldehyde Formaldehyde ( , ) ( systematic name methanal) is a naturally occurring organic compound with the formula and structure . The pure compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde (refer to section ...
in the finished product, often seen with urea-formaldehyde bonded products.


Properties

Plywood and OSB typically have a
density Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematicall ...
of . For example, plywood sheathing or OSB sheathing typically has a surface density of . Many other engineered woods have densities much higher than OSB.


Adhesives

The types of adhesives used in engineered wood include: * Urea-formaldehyde resins (UF): most common, cheapest, and not waterproof. *
Phenol formaldehyde resin Phenol formaldehyde resins (PF) or phenolic resins (also infrequently called phenoplasts) are synthetic polymers obtained by the reaction of phenol or substituted phenol with formaldehyde. Used as the basis for Bakelite, PFs were the first commerc ...
s (PF): yellow/brown, and commonly used for exterior exposure products. * Melamine-formaldehyde resins (MF): white, heat, and water-resistant, and often used in exposed surfaces in more costly designs. * polymeric Methylene diphenyl diisocyanate (pMDI) or
polyurethane Polyurethane (; often abbreviated PUR and PU) refers to a class of polymers composed of organic units joined by carbamate (urethane) links. In contrast to other common polymers such as polyethylene and polystyrene, polyurethane is produced from ...
(PU) resins: expensive, generally waterproof, and does not contain formaldehyde, notoriously more difficult to release from platens and engineered wood presses. A more inclusive term is ''structural composites''. For example,
fiber cement siding Fiber cement siding ("fibre cement cladding" in the United Kingdom and "fibro" in Australia) is a building material used to cover the exterior of a building in both commercial and domestic applications. Fiber cement is a composite material m ...
is made of cement and wood fiber, while cement board is a low-density cement panel, often with added resin, faced with fiberglass mesh.


Health concerns

While
formaldehyde Formaldehyde ( , ) ( systematic name methanal) is a naturally occurring organic compound with the formula and structure . The pure compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde (refer to section ...
is an essential ingredient of
cellular metabolism Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run c ...
in
mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur ...
s, studies have linked prolonged inhalation of formaldehyde gases to cancer. Engineered wood composites have been found to emit potentially harmful amounts of formaldehyde gas in two ways: unreacted free formaldehyde and the chemical decomposition of resin adhesives. When exorbitant amounts of formaldehyde are added to a process, the excess will not have any additive to bond with and may seep from the wood product over time. Cheap urea-formaldehyde (UF) adhesives are largely responsible for degraded resin emissions. Moisture degrades the weak UF molecules, resulting in potentially harmful formaldehyde emissions. McLube offers release agents and platen sealers designed for those manufacturers who use reduced-formaldehyde UF and melamine-formaldehyde adhesives. Many oriented strand board (SB) and plywood manufacturers use phenol-formaldehyde (PF) because phenol is a much more effective additive. Phenol forms a water-resistant bond with formaldehyde that will not degrade in moist environments. PF resins have not been found to pose significant health risks due to formaldehyde emissions. While PF is an excellent adhesive, the engineered wood industry has started to shift toward polyurethane binders like pMDI to achieve even greater water resistance, strength, and process efficiency. pMDIs are also used extensively in the production of rigid polyurethane foams and insulators for refrigeration. pMDIs outperform other resin adhesives, but they are notoriously difficult to release and cause buildup on tooling surfaces.


Mechanical fasteners

Some engineered wood products, such as DLT, NLT, and some brands of CLT, can be assembled without the use of adhesives using mechanical fasteners or joinery. These can range from profiled interlocking jointed boards, proprietary metal fixings, nails or timber dowels.


Building codes and standards

Throughout the years mass timber was used in buildings, codes were added to and adopted by the International Building Code (IBC) to create standards for them for the proper use and handling. For example, in 2015, CLT was incorporated into the IBC. The 2021 IBC is the latest issue of building codes, and has added three new codes regarding construction with timber material.  The new three construction types go as follows, IV-A, IV-B, and IV-C, and they allow mass timber to be used in buildings up to 18, 12, and nine stories respectively. The following standards are related to engineered wood products: * EN 300 - Oriented Strand Boards (OSB) — Definitions, classification, and specifications * EN 309 - Particleboards — Definition and classification * EN 338 - Structural timber - Strength classes * EN 386 - Glued laminated timber — performance requirements and minimum production requirements * EN 313-1 - Plywood — Classification and terminology Part 1: Classification * EN 313-2 - Plywood — Classification and terminology Part 2: Terminology * EN 314-1 - Plywood — Bonding quality — Part 1: Test methods * EN 314-2 - Plywood — Bonding quality — Part 2: Requirements * EN 315 - Plywood — Tolerances for dimensions * EN 387 - Glued laminated timber — large finger joints - performance requirements and minimum production requirements * EN 390 - Glued laminated timber — sizes - permissible deviations * EN 391 - Glued laminated timber — shear test of glue lines * EN 392 - Glued laminated timber — Shear test of glue lines * EN 408 - Timber structures — Structural timber and glued laminated timber — Determination of some physical and mechanical properties * EN 622-1 - Fibreboards — Specifications — Part 1: General requirements * EN 622-2 - Fibreboards — Specifications — Part 2: Requirements for hardboards * EN 622-3 - Fibreboards — Specifications — Part 3: Requirements for medium boards * EN 622-4 - Fibreboards — Specifications — Part 4: Requirements for soft boards * EN 622-5 - Fibreboards — Specifications — Part 5: Requirements for dry process boards (MDF) * EN 1193 - Timber structures — Structural timber and glued laminated timber - Determination of shear strength and mechanical properties perpendicular to the grain * EN 1194 - Timber structures — Glued laminated timber - Strength classes and determination of characteristic values * EN 1995-1-1 - Eurocode 5: Design of timber structures — Part 1-1: General — Common rules and rules for buildings * EN 12369-1 - Wood-based panels — Characteristic values for structural design — Part 1: OSB, particleboards, and fibreboards * EN 12369-2 - Wood-based panels — Characteristic values for structural design — Part 2: Plywood * EN 12369-3 - Wood-based panels — Characteristic values for structural design — Part 3: Solid wood panels * EN 14080 - Timber structures — Glued laminated timber — Requirements * EN 14081-1 - Timber structures - Strength graded structural timber with rectangular cross-section - Part 1: General requirements * ISO 21930:2017 - Sustainability in buildings and civil engineering works - Core rules for environmental product declarations of construction products and services


Examples of mass timber structures


Plyscrapers

Plyscraper A plyscraper, or timber tower is a skyscraper made (at least partly) of wood. They may alternatively be known as mass timber buildings. Materials There are four main types of engineered wood used for mass timber including cross-laminated timbe ...
s are skyscrapers that are either partially made of wood or entirely made of wood. Around the world, there have been many different plyscrapers built including
Ascent MKE Ascent MKE is a mass timber hybrid high-rise apartment building in Milwaukee, Wisconsin. The 284-foot (87 meter), 25-story high-rise is the world's tallest mass timber structure, edging out Norway's Mjøstårnet. It features 259 luxury apartments ...
building and the Stadthaus building. The Ascent MKE building was built in 2022 in
Milwaukee Milwaukee ( ), officially the City of Milwaukee, is both the most populous and most densely populated city in the U.S. state of Wisconsin and the county seat of Milwaukee County. With a population of 577,222 at the 2020 census, Milwaukee i ...
, Wisconsin and is the tallest high-rise building using different mass timber components in combination with some steel and concrete.  This plyscraper is 87 meters tall and has 25 stories. The Stadthaus building is a residential building built in 2009 in
Hackney, London Hackney is a district in East London, England, forming around two-thirds of the area of the modern London Borough of Hackney, to which it gives its name. It is 4 miles (6.4 km) northeast of Charing Cross and includes part of the Quee ...
.  It has 9 stories reaching 30 meters tall.  It uses CLT panels as load-bearing walls and floor ‘slabs’.


Bridges

The Mistissini Bridge built in
Quebec Quebec ( ; )According to the Canadian government, ''Québec'' (with the acute accent) is the official name in Canadian French and ''Quebec'' (without the accent) is the province's official name in Canadian English is one of the thirte ...
, Canada, in 2014 is a 160-meter-long bridge that features both glulam beams and CLT panels.  The bridge was designed to cross over the Uupaachikus Pass. The Placer River Pedestrian Bridge built in
Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U ...
, United States, in 2013.  It spans long and is located in the
Chugach National Forest The Chugach National Forest is a United States National Forest in south central Alaska. Covering portions of Prince William Sound, the Kenai Peninsula and the Copper River Delta, it was formed in 1907 from part of a larger forest reserve. The C ...
.  This bridge features glulam as it was used create the trusses.


Parking structures

The Glenwood CLT Parking Garage in Springfield, Washington, is going to be a garage that features CLT.  It will be 4 stories tall and hold 360 parking spaces.  The parking garage however is under construction , and the year of competition is not yet known.


Notes


References


External links


APA The Engineered Wood Association

Canadian Wood Council Engineered Wood Products

Engineered Wood Products Association
{{DEFAULTSORT:Engineered Wood Composite materials Building materials