Lumber and wood sheet goods are among the most popular in building materials. From framing lumber to appearance boards, they make up a vast majority of your home’s structure. We’ll walk you through the types of lumber and plywood or wood sheets, show you the differences between nominal and actual sizes and even walk you through the different grades of lumber so that you’re sure to get the best lumber for your next project.
Types of Lumber and Plywood
Types of Lumber and Wood Sheet Products
Plywood is made by gluing and pressing plies of veneer together. The more plies in a sheet, the stronger the plywood. Plywood is available in special order widths and lengths as well as standard 4' x 8' (1.2m x 2.4m) sheets with nominal thicknesses from 1/8" (3mm) to 1-1/8" (28mm).
Exterior Plywood (or Appearance-Grade Plywood)
This plywood, and its outer veneers, are made using water-resistant wood and glue making it ideal for sheathing, siding or panelling.
Interior Plywood (or Engineered-Grade Plywood)
Made with water-resistant glue, but its veneers do not weather well. Interior plywood is perfect for concrete forms, sheathing and subfloors. Remember, all plywood should be sealed and painted before exposure to weather and water.
Types of Plywood
Plywood is typically used to support floors, walls and roofs in residential projects and is a popular choice due to its strength and durability. You can find sanded plywood for projects such as shelves and unfinished sheathing plywood, which can be used for roofing and framing.
Hardwood plywood is manufactured for interior finish uses such as cabinets, doors and furniture, and graded on both front and back veneers. With cores made of particleboard, fibreboard, or a combination of the two, hardwood plywood is quite durable. Common species of hardwood plywood include birch, oak and maple.
Un-sanded softwood plywood is primarily used for structural applications such as roofs, walls and floors due to its strength and durability. Sanded softwood plywood is used mainly in concrete formwork and non-structural applications. Common species of softwood plywood include pine and fir.
Medium-Density Fibreboard (MDF) is made by compressing recovered and recycled wood fibre to form an engineered wood product and costs a fraction of the price of solid wood. Standard MDF is ideal for building countertops, doors, furniture, cabinets and shelving.
Moisture-resistant MDF is recommended for interior applications where there is the risk of occasional wetting or prolonged exposure to high levels of humidity.
Deck and Fence Lumber
Lumber used to build decks and fences must be able to stand up to the sometimes harsh Canadian elements and be able to withstand rot and decay.
Typically, the most popular choices for deck and fence lumber are:
Cedar is naturally rot- and decay-resistant and is also resistant to insects as well. It is also less prone to moisture absorption, so it is less likely to warp and split.
Pressure-treated lumber is processed with preservatives to help it last longer, avoid rot and decay and is generally less expensive than cedar lumber. It can be stained or painted easily and is great for any exterior-use projects.
Framing lumber or dimensional lumber is often referred to as wall studs, which are the vertical 2 x 4 beams supporting the frame of your home. Wall studs are found behind the drywall and are usually spaced anywhere from 16 – 24 inches apart, with 16 inches being most common for interior walls. The most common framing lumber is SPF or spruce-pine-fir lumber. This is known as dimensional lumber, and is commonly referred to by size, including 2x4, 4x4, etc.
Similar to MDF, hardboard is constructed of wood fibres and softwood pulp, and considered to be fibreboard. The primary difference between MDF and hardboard lies in the density of the panel and the additives that make them specially suited for different applications.
Medium-density hardboard can be used for doors, soffits and other applications where it can be protected from moisture and weather. High-density hardboard can be used for curved forms.
Perforated hardboard or pegboard is moisture resistant and commonly used on walls in garages and workshops for organization and storage.
Particleboard is made of wood particles (approximately sawdust size) bonded with resins and formed into panels under heat and pressure. These panels are used primarily for floor underlayment and in manufacturing cabinets, laminate countertops and doors. Particleboard makes better underlayment than plywood because there are no voids in the core that might dent under resilient flooring, and it also makes a good base for countertop laminates because of its smoothness and stability. However, particleboard has little structural strength, and a tendency to swell and disintegrate when it gets wet.
Oriented Strand Board (OSB)
Oriented Strand Board (OSB) structural panels are manufactured using wood strands and waterproof adhesives. The wood strands are arranged in cross-oriented layers to provide strength and performance properties similar to plywood. OSB has a consistent quality with no gaps or voids. Common uses of OSB in residential construction include subflooring, roof sheathing, wall sheathing, concrete forms, ceilings and soffits.
Nominal vs. Actual Lumber Size
The nominal size of lumber is the rough dimension of the lumber before it is trimmed to its final size – this is what you’ll see mentioned in project guides and on the tags at your local store. The actual size is noted below.
|Nominal Size||Actual Size|
|1 x 4||¾ x 3 ½ inches|
|1 x 6||¾ x 5 ½ inches|
|2 x 2||1 ½ x 1 ½ inches|
|2 x 4||1 ½ x 3 ½ inches|
|2 x 6||1 ½ x 5 ½ inches|
|2 x 8||1 ½ x 7 ¼ inches|
|2 x 10||1 ½ x 9 ¼ inches|
|4 x 4||3 ½ x 3 ½ inches|
In Canada, lumber and wood sheet products are graded by the Canadian Lumber Standards Accreditation Board (CLS) based on a number of factors.
Wood panel products are graded according to their intended use, therefore only its appearance and structural properties are judged for adequacy.
- A = Cabinet Grade
- B = Sanded Grade
- C or C plugged = Sheathing Grade
"A" veneer on face, "B" veneer on back
"A" veneer on face, "C" veneer on back
"B" veneer on face, "C" veneer on back
"C" veneer, filled and touch sanded on face, "C plugged" veneer on back