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LumberLumber for structural applications such as walls, floors, and ceilings is usually milled from strong softwoods and is categorized by grade, moisture content, and dimension.

Grade: Characteristics such as knots, splits, and grain slope affect the strength of the lumber and determine the grade. Moisture content: Lumber is also categorized by moisture content. S-DRY (surfaced dry) is the designation for lumber with a moisture content of 19 percent or less. S-DRY lumber is the least likely to warp or shrink and is a good choice for framing walls. S-GRN (surfaced green) means the lumber contains a moisture content of 19 percent or more.

Exterior lumber: Lumber milled from redwood or cedar is naturally resistant to decay and insect infestation and is a good choice for exterior applications. The most durable part of a tree is the heartwood, so specify heartwood for pieces that will be in contact with the ground.

Treated lumber: Lumber injected with chemicals under pressure is resistant to decay and is generally less expensive than decay-resistant heartwoods such as redwood and cedar. For outdoor structures like decks, use treated lumber for posts and joists and more attractive redwood or cedar for decks and railings.

Dimension lumber: Lumber is sold according to its nominal size, such as 2×4. Its actual size is smaller. Always use actual sizes for measuring and estimating.

Lumber Grading Chart

Much of today’s lumber is still fairly wet when it is sold, so it’s hard to predict how it will behave as it dries. But a quick inspection of each board at the lumberyard or home center will help you disqualify flawed boards. Lumber that is cupped, twisted, or crooked should not be used at full length. However, you may be able to cut out good sections for use as blocking or other short framing pieces. If a board is slightly bowed, you can probably flatten it out as you nail it. Checks, wanes, and knots are cosmetic flaws that seldom affect the strength of the board. The exception is a knot that is loose or missing. In this case, cut off the damaged area. Sections with splits should also be cut off. Splits are likely to spread as the wood dries.

Description, uses
Clear Free of knots and defects
SEL STR or Select Structural Good appearance, strength, and stiffness
1, 2, 3 1, 2, 3 grades indicate knot size
CONST or Construction Both grades used for general framing
STAND or Standard Good strength and serviceability
STUD or Stud Special designation used in any stud application, including load-bearing walls
UTIL or Utility Economical choice for blocking and bracing

Selecting the Right Lumber for a Project

1aPicking the right wood for a project is a decision that will affect the durability and attractiveness of the final product. Some woods are more prone to warping than others, some are more resistant to decay, and some are superior when it comes to accepting a coat of paint. Matching styles and wood varieties will help to create a common theme throughout your home.

Lumber sizes such as 2×4 are nominal dimensions, not actual dimensions. The actual size of lumber is slightly smaller than the nominal size. When it is originally milled, lumber is cut at the nominal size; however, the boards are then planed down for a smoother finish, producing the actual dimensions you buy in the store. See the chart on the opposite page for nominal and actual dimensions.

Cedar Easy to cut, holds paint well. Heartwood resists decay. Decks, shakes, shingles, posts,and other decay-prone surfaces.
Fir, larch Stiff, hard wood. Holds nails well. Some varieties are hard to cut. Framing materials, flooring,and subflooring.
Pine Lightweight, soft wood with a tendency to shrink.Holds nails well. Some varieties resist decay. Paneling, trim, siding, and decks.
Redwood Lightweight, soft wood that holds paint well. Easy to cut. Heartwood resists decay and insect damage. Outdoor applications, such as decks, posts, and fences.
Treated lumber Chemically treated to resist decay. Use corrosion-resistant fasteners only. Wear protective eye wear and clothing to avoid skin, lung, and eye irritation. Ground-contact and other outdoor applications where resistance to decay is important.


Birch Hard, strong wood that is easy to cut and holds paint well. Painted cabinets, trim, and plywood.
Maple Heavy, hard, strong wood that is difficult to cut with hand tools. Flooring, furniture, and countertops.
Poplar Soft, light wood that is easy to cut with hand or power tools. Painted cabinets, trim, tongue-and-groove paneling, and plywood cores.
Oak Heavy, hard, strong wood that is difficult to cut with hand tools. Furniture, flooring, doors, and trim.
Walnut Heavy, hard, strong wood that is easy to cut. Fine woodwork, paneling, and mantelpieces.

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