2.4: Lumber Surfaces and Dimensions
- Page ID
- 67168
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2.4 Lumber Surfaces and Dimensions
A woodworker needs a common vocabulary for describing a board.
Before you can accurately discuss milling, drawings, cut lists, or project parts, you need to know the names of the surfaces and understand how hardwood lumber is sized.
Learning Outcomes
After completing this section, you should be able to:
- Identify the face, edge, and end of a board.
- Identify thickness, width, and length.
- Explain common lumber-surfacing terms.
- Interpret quarter-inch hardwood thickness notation.
- Explain the difference between rough and finished dimensions.
The Surfaces of a Board
A rectangular board has three pairs of surfaces.
Faces — The two broad surfaces of the board.
Edges — The two narrow surfaces running along the length of the board.
Ends — The two surfaces across the ends of the board, where end grain is visible.
These terms matter because woodworking operations often refer specifically to a face, edge, or end.
For example:
- You may flatten a face on the jointer.
- You may straighten an edge on the jointer.
- You may square an end on a saw.
Figure: Board Surfaces and Dimensions
Dimension Order
Lumber dimensions are listed in this order:
Thickness × Width × Length
For example:
3/4 in. × 6 in. × 14 in.
means:
- 3/4 inch thick;
- 6 inches wide; and
- 14 inches long.
Get into the habit of using this order consistently. You will see it in drawings, cut lists, bills of materials, and project plans throughout woodworking.
Rough and Surfaced Lumber
Rough lumber has not been surfaced smooth after sawing at the mill.
Surfaced lumber has had one or more surfaces machined.
Common abbreviations include:
S1S — Surfaced one side, usually one face.
S2S — Surfaced two sides, usually both faces.
S3S — Surfaced three sides, usually both faces and one edge.
S4S — Surfaced four sides: both faces and both edges.
You may also see terminology such as:
SLR1E — Straight-line ripped one edge.
For example, S2S SLR1E describes lumber with both faces surfaced and one edge straight-line ripped.
Hardwood Thickness: Quarter Notation
Rough hardwood thickness is commonly specified in quarters of an inch.
|
Hardwood Size |
Nominal Rough Thickness |
|---|---|
|
4/4 |
1 in. |
|
5/4 |
1 1/4 in. |
|
6/4 |
1 1/2 in. |
|
8/4 |
2 in. |
|
10/4 |
2 1/2 in. |
|
12/4 |
3 in. |
A woodworker would commonly say “four-quarter,” “five-quarter,” “six-quarter,” or “eight-quarter.”
Rough Size Is Not Finished Size
The quarter measurement describes the approximate thickness of the lumber before it is surfaced.
Surfacing always removes some material.
How much is removed depends on how flat and straight the rough board is. A relatively flat board may require little material removal, while a badly warped board may lose considerably more.
For example, you should not expect a rough 4/4 board to remain a full 1 inch thick after both faces have been flattened and surfaced.
Always select rough stock thick enough to reach the required finished dimension after milling.
This is especially important when working with warped or irregular lumber. A board may appear thick enough when rough but become too thin by the time enough material has been removed to make it flat.
Dimensional Lumber Is Different
Construction lumber follows a different sizing system.
A familiar 2 × 4, for example, does not finish at 2 inches by 4 inches. Its actual surfaced dimensions are smaller.
Do not confuse construction-lumber terminology with the quarter system commonly used for rough hardwood.
Check Yourself
- What are the three types of surfaces on a board?
- In what order are lumber dimensions written?
- What does S2S mean?
- What does S4S mean?
- What is the nominal rough thickness of 6/4 lumber?
- Why does rough lumber finish thinner after milling?