Engineered wood
[2] These products are engineered to precise design specifications, which are tested to meet national or international standards and provide uniformity and predictability in their structural performance.
Some engineered wood products, like oriented strand board (OSB), can use trees from the poplar family, a common but non-structural species.
Non-structural panels are usually covered with paint, wood veneer, or resin paper in their final form.
[9] Plywood is manufactured from sheets of cross-laminated veneer and bonded under heat and pressure with durable, moisture-resistant adhesives.
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.
Particle board is manufactured from wood chips, sawmill shavings, or even sawdust, and a synthetic resin or another suitable binder, which is pressed and extruded.
[14] 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.
Structural composite lumber (SCL) is a class of materials made with layers of veneers, strands, or flakes bonded with adhesives.
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.
Parallel-strand lumber (PSL) consists of long veneer strands laid in parallel formation and bonded together with an adhesive to form the finished structural section.
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.
[17] 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.
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.
[23] 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.
The biggest benefit of this method is that no glue or metal is needed,[24] thus eliminating VOCs (such as formaldehyde) associated with wood adhesives used in most other engineered timbers.
Similar to CLT, DLT uses a cross laminated pattern with softwoods, but instead of wood adhesives to fix lumbers in place, holes are drilled vertically or in a 45° angle, and 15-20mm dowels made of dry hardwood or densified wood (such as thermal-compressed) are placed between the lumbers.
[29] Studies published in 2018[30] combined chemical processes with traditional mechanical hot press methods.
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.
Other suggestions include hybridizing natural wood with other organic particles and polymers to enhance its thermal insulation performance.
However, initial tests show promising advantages in improved mechanical properties, with the molded wood exhibiting strength comparable to some metal alloys.
Engineered wood has the potential to reduce carbon emissions if it replaces steel and/or concrete in the construction of buildings.
When excessive amounts of formaldehyde are added to a process, the surplus will not have any additive to bond with and may seep from the wood product over time.
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.
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.
[54] 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,[55][56] proprietary metal fixings, nails or timber dowels.
[62] As of 2022, over 84 mass timber buildings at least eight stories tall were in construction or completed worldwide, with numerous other projects in the planning stages.
