Engineered wood, also known as manufactured wood or composite wood, is revolutionizing the construction industry. Instead of relying solely on solid lumber, engineered wood products offer a versatile and often superior alternative for a wide array of building applications. But What Is Engineered Wood exactly?
Simply put, engineered wood is created by binding together wood strands, fibers, veneers, or other forms of wood with adhesives to form composite materials. This process allows manufacturers to optimize the characteristics of wood for specific structural and aesthetic purposes. Often made from fast-growing younger trees and even wood waste, engineered wood is also frequently touted as a more sustainable option compared to traditional lumber.
“Engineered lumber is lumber that although it comes from wood, it’s been processed to be something slightly different and perform in a different, oftentimes better way than what just the raw wood would perform.” -Professional builder Jordan Smith
From the framing of your house to the furniture inside, engineered wood is incredibly versatile. Let’s delve into the popular types of engineered wood and explore their advantages and disadvantages.
7 Common Types of Engineered Wood Products
Engineered wood products come in various forms, each designed for specific applications. They can be broadly categorized as framing members, like beams and joists, and sheet goods, which are ideal for sheathing, flooring, and wall panels. Here are seven of the most popular types:
1. Laminated Veneer Lumber (LVL)
Laminated Veneer Lumber, or LVL, is a high-strength engineered wood product primarily used for structural framing. It’s manufactured by layering thin wood veneers, aligning the wood grain in the same direction, and bonding them together using adhesives under heat and pressure. This process results in a dense, strong, and reliable lumber alternative.
LVL is exceptionally strong in the direction of the grain, making it ideal for beams, headers, and rim boards where high bending strength is required. However, because the grain runs in only one direction, its strength is directional, meaning it’s designed to bear loads applied in a specific orientation.
2. Laminated Strand Lumber (LSL)
Laminated Strand Lumber, or LSL, takes engineered wood strength and density a step further. It’s made from shredded wood strands that are oriented and then bonded together with adhesives. The strands in LSL are arranged in a dense, angled pattern, contributing to its exceptional strength and stiffness.
Composed of approximately 95% wood fiber and 5% resin, LSL can be even denser and stronger than LVL. The angled arrangement of wood strands provides resistance to both weight and torsion, making it suitable for demanding structural applications. While offering superior performance, LSL is also a more premium product, often costing significantly more (around 3x) than traditional dimensional lumber.
3. Oriented Strand Board (OSB)
Oriented Strand Board, commonly known as OSB, is a widely used sheet good in construction. It’s manufactured by compressing layers of wood strands or flakes, oriented in specific directions for added strength, with adhesives. OSB is produced in large mats, making it cost-effective for covering large areas.
OSB is particularly well-suited for load-bearing applications such as subflooring, roof decking, and wall sheathing. However, it’s crucial to recognize that OSB quality varies. Some premium OSB products, like Advantech or Legacy subflooring, are sanded for a smoother surface and may offer enhanced moisture resistance. For applications exposed to the elements, premium, moisture-resistant OSB is highly recommended.
When installing OSB (and plywood), remember to leave a small gap at the ends of panels. This allows for expansion and contraction due to changes in moisture content, preventing buckling. Premium subflooring often features tongue-and-groove edges with a built-in stop to automatically create this necessary gap.
4. Plywood
Plywood is another familiar sheet good, constructed from thin layers of wood veneer, called “plies,” glued together. The key to plywood’s strength and stability lies in its “cross-graining” construction. Each layer’s grain runs perpendicular to the layers above and below, creating dimensional stability and consistent strength across the entire panel.
Like OSB, plywood benefits from gapping during installation to accommodate expansion and contraction. Plywood is graded based on the quality of its face veneers, with common grades including:
- A-Grade: The highest quality, smooth, and free of knots and repairs.
- B-Grade: Mostly clear, with limited small, tight knots allowed.
- C-Grade: May contain knots up to 1.5 inches and smaller knotholes.
- D-Grade: The lowest grade, allowing larger knots and knotholes, typically unrepaired.
- X-Grade: Indicates exterior-grade plywood, suitable for outdoor use. For example, CDX plywood would have a C-grade veneer on one side, D-grade on the other, and is designed for exterior applications.
5. Medium Density Fiberboard (MDF)
Medium Density Fiberboard, or MDF, is produced from hardwood and softwood residuals broken down into fine fibers. These fibers are then combined with resin and wax binders and pressed into panels under high heat and pressure. MDF is denser than both plywood and OSB, providing a very smooth and stable surface.
Like OSB, MDF is available in different grades, with some formulated to resist moisture and weather, while others are not. MDF is commonly used for furniture, cabinetry, and interior trim due to its smooth surface and ease of machining.
6. Composite Board
The term “composite board” in engineered wood can sometimes be used broadly, encompassing MDF and OSB. However, it also specifically refers to a type of engineered wood that combines wood fiber with plastic content. This material is often extruded and heated, resulting in a durable and moisture-resistant product. It’s also frequently referred to simply as “engineered wood” in certain contexts, particularly when discussing decking or siding materials.
Composite boards are gaining popularity for their ease of installation, cost-effectiveness, and sustainability advantages. They can be manufactured from recycled materials, reducing reliance on virgin timber and promoting environmentally conscious design.
7. Cross-Laminated Timber (CLT)
Cross-Laminated Timber, or CLT, represents a significant innovation in engineered wood for construction. CLT panels are made by layering solid-sawn lumber boards, with each layer oriented perpendicular to the next. These layers are then bonded together with adhesives on their wide faces.
This cross-lamination technique gives CLT exceptional strength and dimensional stability in multiple directions. The thickness of CLT panels can be easily adjusted by adding more layers, making it a versatile material for walls, floors, and roofs. CLT also offers good insulation properties due to its multi-layered wood construction and is increasingly recognized for its sustainable building potential.
Pros and Cons of Engineered Wood Compared to Solid Wood
“Engineered beams are a great way of getting the strength while keeping the cost and size low.” -Professional builder Jordan Smith
Engineered wood has become increasingly popular, particularly in flooring and structural applications, due to a range of benefits. However, it’s important to consider both the advantages and disadvantages when choosing between engineered wood and solid wood.
Advantages of Engineered Wood:
- Sustainability: Engineered wood often utilizes younger, faster-growing trees and wood waste, making it a more sustainable alternative to old-growth timber. It maximizes wood fiber utilization, reducing waste in the manufacturing process.
- Strength and Consistency: Engineered wood can be engineered to meet or exceed the strength and density of solid wood. The layered construction and controlled manufacturing processes result in more consistent and predictable performance.
- Larger Sizes and Design Flexibility: Engineered wood products, like LVL and glulam beams, can be manufactured in much larger sizes than solid lumber, opening up design possibilities and reducing the need for support columns.
- Resistance to Warping and Splitting: Many engineered wood products are less prone to warping, twisting, and splitting compared to solid lumber due to the controlled drying and manufacturing processes.
- Cost-Effectiveness: In many cases, engineered wood can be a more cost-effective alternative to solid wood, especially for structural applications requiring high strength or large dimensions.
Disadvantages of Engineered Wood:
- Aesthetics: Some engineered wood products, particularly those with visible strands or layers, may not have the same natural aesthetic appeal as solid wood for certain applications where appearance is critical. However, products like architectural-grade glulam are designed to be visually appealing.
- Cost (Specific Types): Certain high-performance engineered wood products, like LSL, can be significantly more expensive than dimensional lumber.
- Moisture Sensitivity: While some engineered wood products are moisture-resistant, many are still susceptible to moisture damage if not properly protected or treated. It’s important to select the appropriate type of engineered wood for the intended environment.
- Formaldehyde Concerns: Historically, some engineered wood products used formaldehyde-based adhesives. However, modern manufacturing standards have largely shifted to low- or no-formaldehyde options. It’s advisable to check product specifications to ensure low VOC emissions, especially for indoor applications.
Engineered wood is a dynamic and evolving category of building materials. Understanding what engineered wood is, its various types, and its pros and cons is crucial for making informed decisions in construction and design. As technology advances, engineered wood will likely continue to play an increasingly important role in creating sustainable, efficient, and high-performing buildings.
Learn more about wood properties and applications in construction with MT Copeland’s online course on Wood Materials. Taught by professional builder Jordan Smith, this course provides in-depth knowledge on topics ranging from wood selection to advanced framing techniques.
