Types of Lumber

There are two categories of wood: hardwood and softwood. The lumber industry uses a scale called the Janka Rating System. This scale measures and ranks the relative hardness of wood. Hickory is the hardest, commercially available common wood. Next in line are pecan, hard maple and white oak.

Hardwood includes wood like hickory, oak, mahogany, maple and walnut. If you’re unsure what wood you’re working with, perform a quick test by pressing your fingernail into the wood. If it is hardwood, it will not dent easily. Ultimately, the types of hardwood you choose will depend on your project and the look you are trying to achieve. 

• Typically used in cabinetry, flooring and woodworking.
• Usually requires more upfront investment than softwood.

Softwood includes cedar, pine, spruce and fir wood.  Press your fingernail into the wood. If it dents easily, it’s softwood. The types of softwood you choose depends on the purpose and look of the project. Softwood absorbs moisture easily. Choose pressure-treated options for outdoor projects. 

• Typically used in DIY projects or home construction.
• More budget-friendly than hardwoods.

Popular varieties of lumber include:

• Pine is budget-friendly and easy to find. It is typically used in furniture building and construction.
• Poplar is used in cabinet-making, painted furniture, ceiling moldings and trim. It gives the look of expensive hardwood when stained but is easily scratched.
• Redwood works well for outdoor projects. It naturally resists rot and is more attractive than pressure-treated wood.
• Cedar resists rot, especially when treated regularly with a preservative. It is a popular and highly attractive choice for outdoor projects.

While terms like boards, studs and plywood all refer to types of lumber, they should not be used interchangeably. Each type of lumber is designed to be used for specific building purposes. Read on for a breakdown of the most commonly used types of wood as well as their features and benefits. 

The most commonly used lumber, structural lumber, are the 2-inch x 4-inch and 4-inch x 4-inch boards used in everyday DIY and construction projects. 

Framing and structural lumber follows standard building dimensions (thickness and width). Standard dimensions allow for faster building as less cutting is needed on site. 

Structural lumber can be broken down into seven categories: 

• Light framing lumber is 2 inches to 4 inches thick and 4 inches wide.
• Structural light framing is 2 inches to 4 inches thick and 2 inches to 4 inches wide.
• Dimensional lumber and studs are 2 inches to 4 inches thick and 2 inches to 4 inches wide.
• Structural joists and planks are 2 inches to 4 inches thick and 6 inches wide.
• Beams and stringers are at least 5 inches wide and 2 inches thick.
• Posts and timbers are usually 5-inch x 5-inch boards.
• Appearance framing lumber is 2 inches wide and 1-inch thick.

Appearance boards are chosen primarily based on how they look rather than their strength. They must be at least 1-inch thick and 2 inches wide. There are two grades of appearance boards, "Finish" (a higher grade) and "Select". Appearance boards are ideal for shiplap projects, DIY crafts, interior furniture and decor.

Appearance boards can be used untreated or painted/stained. They are available in hardwoods, softwoods, reclaimed wood and barn wood boards. 

Plywood is made from layers of thin sheets of wood and cured under heat and pressure. It's ideal for DIY crafts, shelving and subfloors. Plywood can be used untreated, painted or stained. It's available in hardwood and softwood veneers.

MDF, or Medium-Density Fiberboard, is a combination of hardwood and softwood bound with resin. It's denser than plywood but is not very moisture resistant. MDF is ideal for the unseen parts of cabinets, interior furniture or shelving.

Deck and fencing lumber includes railings, floor boards, posts and balusters. It is available with above-ground contact or ground contact treatment.

• Composite deck lumber is made of a combination of wood and plastic, making it dense and durable.
• Wood decking boards are durable and budget-friendly.
• Composite decking boards are available in a range of colors and won’t warp or crack.
• Deck tiles create custom patterns on deck surfaces with an interlocking tile system.

Pressure-treated lumber is wood that has been processed with preservatives to last longer. It is available with above-ground contact or ground contact treatment.

• Choose from wood decking boards, composite decking boards and deck tiles.
• Wood decking boards are durable and budget-friendly.
• Composite decking boards are available in a range of colors and won’t warp or crack.
• Great for exterior use and projects that come in contact with cement. It is rot-resistant and can be painted or stained easily.
• Heavier than untreated lumber, so it tends to require more upfront investment.
• Many of the chemicals used in pressure treating lumber contain pesticides.

Untreated lumber is great for projects involving animals, children or plants. Some types of lumber, like cypress and redwood, are naturally rot-resistant. Untreated lumber is also lighter, easier to cut and budget-friendly. 

Grade refers to both the appearance and strength of the lumber. Hardwood and softwood have their own grading systems. Lumber grading determines both price and how the wood will be used. Strong lumber with fewer knots or cosmetic blemishes gets a higher grade and price. Some types of lumber may be marked as "premium" by the manufacturer, but this is not a standard grade. "Premium" refers to the clean appearance of the board but doesn't verify the strength or physical quality. 

Hardwood is graded by the National Hardwood Lumber Association. Hardwood grades are:

• FAS (First and Second) is the highest grade of hardwood lumber. It’s usually 6-inches x 8-inches and is 83 percent defect-free on its best side.
• Select is 4-inches x 6-inches and 83 percent defect free on its best side.
• No. 1 Common is 3-inches x 4-inches and 66 perfect defect free on its best side.
• No. 2 Common is 3-inches x 4-inches and 50 percent defect free on its best side.

Softwood grades typically fall into two categories: dimensional lumber (based on the wood's strength) and appearance boards (most commonly used for woodwork). 

• C Select has little to no defects and is used for cabinets and trim.
• D Select has a few more defects than C select. It’s great for projects that will be painted.
• No. 1 Common is a standard grade lumber with a knotty look.
• No. 2 Common has larger knots. It’s good for paneling and shelving.
• No. 3 Common has larger knots than No. 2 Common. It’s best for shelving, paneling, pallets and fences.

Tip: Sometimes "prime" is listed with the grade, such as "prime FAS grade." This lumber has both the qualities of the FAS grade and a fine appearance. Search for prime lumber when the look of the wood is important for a project. 

Lumber is identified by its nominal or named size. The nominal size is the lumber’s rough dimension before it is trimmed to its finished size at the lumber mill. This is the size that appears on the tag in store. Actual lumber sizes are approximate dimensions after trimming. 

For example, for the dimensions of lumber, a tag that says 2 x 4 doesn’t actually mean lumber that’s two inches by four inches in measure. Rather 2 x 4 is in actuality 1-1/2-inch x 3-1/2-inch.

Nominal size is usually the size quoted in DIY project instructions. If actual lumber sizes are required, that will be noted. These measurements clarify what you’ll see on the tag in stores (nominal size) versus the actual measurements of the lumber (actual size).

All wood has natural defects that can add character. There are, however, some defects in structural lumber that you shouldn’t overlook. Here are the most common lumber defects: 

• Bow is a warp on the face of a board from end to end.
• Cup is a hollow across the face of a board.
• Crook or crown is a warp along the edge line.
• Knots are a part of the wood’s grain. A tight knot is usually fine. A loose or dead knot, surrounded by a dark ring, can fall out and leave a hole.
• Twists are multiple bends or warped spots in a board.
• Splits are cracks going all the way through the piece of wood. They’re commonly at the ends and are usually caused by mechanical processing.
• Check is a crack along the wood's annual growth rings. It usually doesn’t pass through the entire thickness of the wood.
• Shake is a crack that splits the wood along the grain. It can pass through the wood’s entire thickness. A shake differs from a split because it’s usually caused by natural growth.
• Wane is bark or missing wood on the sides or edges of lumber.