Wood Basics

In the USA, there are over 1,000 species of trees. Of these, only about 100 are used for constructing and manufacturing wood products. From this group, it's best to pick the ones that are easiest to work with and most appealing to you.

There are basically two kinds of wood from which to choose- hardwoods and softwoods. In addition, there are certain characteristics that are common in all wood types. Here are some common terms and definitions you should know:

HARDWOODS
Hardwoods are the deciduous trees that lose their leaves in the fall. Among an abundant variety, only 200 are plentiful and pliable enough for woodworking. Much like our skin, hardwoods have microscopic pores on the surface. The size of these pores determines the grain pattern and texture. Because of this, hardwoods are classified by pore openings as either: Closed Grained (smaller pores), like cherry and maple; Ring Porous (larger pores), like oak, ash or poplar.

SOFTWOODS
Softwoods come from coniferous trees, commonly referred to as evergreen trees. Only 25 percent of all softwoods are used in woodworking. All softwoods have a closed grain (small pores) that is not very noticeable in the finished product. The most popular softwoods are cedar, fir, pine and spruce.

DENSITY
Heavy woods like oak are identified by their weight and tight grain pattern, and resist wear, dents and scratches better than softwoods.

TEXTURE
This is the wood property that determines the condition of the surface and stability. It plays an important role in deciding how a wood can be finished.

DEFECTS
Defects in wood are natural and are appreciated by many woodworkers for the unique character they contribute.

COLOR
Color contributes to the personality of wood. For example, red cedar will give you a very different look and character than white pine.

GRAIN
Grain is the most well-known wood characteristic. Grain pertains to the wood-cell fibers' orientation. The project you are undertaking dictates the most suitable type of grain.

GRADES
Lumber grades are determined by the number, location and size of defects in the board, not its strength. The clearer the wood, the higher the grade.

STABILITY
This is the wood's ability not to shrink or expand before or after it has been worked.

DURABILITY
Durable woods better resist excess moisture and exposure to the earth, where there's a greater chance of decay. Remember, no wood will decay if it's kept dry.

Wood Grain

Two boards of the same species can look very different. Each tree has its own grain pattern. This is the direction in which the wood cell fibers grow. These variances in grain direction can have a significant impact on your project.

The grain direction is important to consider when building either structural projects or decorative projects such as furniture or crafts. For instance, when working on a structural application, a straight-grained board is generally the strongest. In more decorative projects, grain with varying characteristics can add beauty and personality to the project.

There are six general types of grain:

Diagonal Grain When a straight-grained log is not sawn along its vertical axis, diagonal grain is the result.

Spiral Grain When trees grow twisted, spiral-grained logs and subsequent boards are produced. Fibers follow a spiral course with a twist that is either left- or right-handed.

Straight Grain The board's fibers run approximately parallel with the vertical axis of the log from which it originated.

Wavy Grain This type of grain results when the direction of wood fibers has constantly changed.

Irregular Grain Boards of this type have fibers at directions that are varying and irregular from the log's vertical axis (for example: fibers around knots).

Interlocked Grain Boards with this grain result from trees whose fibers lined up in opposite directions in each growth year.

Grain pattern density determines strength. As you'd expect, a piece of lumber with a tight pattern is stronger than one with a loose grain pattern. And when building, a board's strength is maximized when other pieces run across the grain pattern - not parallel to it.

Hardwood Grades

Grading designation depends on the number of defects in a given length and width of hardwood boards. As with softwoods, a lower grade can be perfectly acceptable, depending on placement and usage. Hardwoods are graded by the National Hardwood Lumber Association. Here's a chart to help explain the grading system. Grades are listed from highest to lowest

Grade Name	Abbreviation	Minimum Board Size	% Usable Material On One Face
First and Seconds	FAS	6" x 8'	83
Select	Sel	4" x 6'	83
#1 Common	#1 Com	3" x 4'	66
#2 Common	#2 Com	3" x 4'	50

Softwood Grades

Softwoods are divided into two categories: dimensional lumber, with a grade based on strength, and appearance boards, which are typically used for woodworking projects. Grading of softwoods is overseen by a number of different agencies, so you will be more likely to find some variations in terminology. Grades listed here are from highest to lowest.

Grade	What It Means
C Select	Almost completely clear of defects. Widely used for interior trim and cabinets.
D Select	Fine appearance, similar to C Select. May have dime-sized knots.
1 Common	Best material for high quality pine with a knotty look. Knots will be tight, meaning they won't fall out and are generally small.
2 Common	Tight knots, but larger than found in 1 Common. Often used for paneling and shelving. Very suitable for general woodworking projects.
3 Common	Knots larger than in 2 Common. Also used for paneling and shelving, but especially well-suited for fences, boxes, and crates.

Common Defects

BOW: Warp on the face of a board from end to end.	CUP: Hollow across the face of a board.
CROOK: Warp along the edge line, also known as crown.	KNOT or KNOTHOLE: A tight knot is usually not a problem. A loose or dead knot, surrounded by a dark ring, may fall out or may have already left a hole.
SPLIT: Crack going all the way through the piece of wood, commonly at the ends.	TWIST: Multiple bends in a board.
CHECK: Crack along the wood's annual growth rings, not passing through the entire thickness of the wood.	SHAKE: Separation of grain between the growth rings, often extending along the board's face and sometimes below its surface.
WANE: Missing wood or untrimmed bark along the edge or corner of the piece.

Grade Stamp

While lumber of the same species and size is at the mill, it is designated and separated by grade. It is then identified by a stamp and often inventoried by its grade and species. When selecting wood, be sure you look for its grading stamp because different lumberyards sometimes use different names for the same grade. (And remember, if you are having trouble figuring it all out, ask for help.) Grade designations depend on particular defects such as knots or wane. Keep your project final results in mind when selecting the grade of wood. Grade does not indicate consistency of color or grain patterns.
Manufacturer: Mill's number, name, or symbol. (ex. 12)
Certification mark: Symbol of agency providing quality-control supervision. (ex. WWP®)
Grade: Often abbreviated. 1 Common shown. (ex. 1COM)
Moisture content (MC): Abbreviation for MC when board surfaced. MC 15 is 15 percent or less; KD or S-DRY is 19 percent or less; S-GRN is green wood with more than 19 percent MC. (Ex. S-DRY)
Species mark: Symbol or abbreviation for types of tree. Example shown is Ponderosa pine. (Ex. PP)

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