Measurements and Pricing of Primary Wood Materials
School of Natural Resources
Not too many years ago, people who bought the primary wood products — lumber, plywood and molding — were carpenters or builders who were familiar with these materials. Today, many homeowners (do-it-yourselfers) get involved with home repair and maintenance.
This guide is for people who would like to know how primary wood building products and wood fuel are sold. For example, many people buy lumber by the board foot, not knowing what a board foot is.
Topics discussed are softwood lumber, panel products such as plywood, wood molding and trim, wood flooring, wood shingles and shakes, wood posts, and cordwood.
When you buy a 2-inch by 4-inch by 10-foot (2 x 4 — ten feet long) piece of lumber, the salesperson may simply price the board by the piece. Or, you may learn that the particular grade of lumber sells for $0.38 per board foot. You need to know how many board feet you are buying or what a board foot (bf) of lumber is. A board foot is commonly defined as a piece of wood 12 inches by 12 inches by 1 inch or 144 cubic inches. Pieces of wood 12 inches by 6 inches by 2 inches or 6 inches by 6 inches by 4 inches represent one board foot because they are both 144 cubic inches.
A formula that incorporates the length in feet and the cross section dimensions in inches can be used to calculate board foot in any piece of lumber:
|Board foot =
||T (inches) x W (inches) x L (feet)
T = thickness in inches
W = width in inches
L = length in inches
For example, the board foot in the 2-inch by 4-inch by 10-foot board referred to above are:
|Board foot =
||2 x 4 x 10 (feet)
At 38 cents per board foot, the board will cost 0.38 x 6.66 = $2.53
Use our interactive Board Foot calculator.
Lumber dimensions. A board foot can be calculated by taking nominal thickness in inches by nominal width in inches by length in feet and dividing by 12.
A characteristic of kiln-dried lumber that confuses people is that 2 x 4s or 2 x 6s are not actually 2 inches by 4 inches or 2 inches by 6 inches. These are the "nominal" or "name only" dimensions. If you measure a finished 2 x 4, you will find it to be 1-1/2 inches by 3-1/2 inches. These are called the "actual" dimensions. No, you haven't made a mistake by calculating the board feet of a piece of lumber with the "nominal" dimensions. This is the common and accepted procedure.
In the manufacture of a piece of lumber, the 2 x 4 is 2 inches by 4 inches or more at the time it is cut in the sawmill. After cutting, lumber shrinks 10 to 15 percent by volume during the drying process. After this, it is planed (surfaced four sides) to the "actual" dimensions (1-1/2 inches x 3-1/2 inches). The surfaces are now smooth, flat and cut to prescribed size. In normal use, it also has a higher degree of stability — that is, it will not shrink or swell as much in normal use. Softwood lumber is sold only in even lengths by feet, such as 10 feet, 12 feet, 14 feet and 16 feet.
Structural lumber, as opposed to appearance lumber, is graded for strength. The grades most commonly encountered are:
- Number 1 common (construction)
- Number 2 common (standard)
- Number 3 common (utility).
There are considerable differences between the grades in price and character (strength properties).
Panel products are building materials made from a wood base and sold in sheets (usually 4 feet by 8 feet) of varying thicknesses. Panel products are not sold by the board foot. They are usually sold by the square foot at a specified thickness. For example, plywood might be $0.42 per square foot for 3/4 inch (thick) material and $0.30 per square foot for 1/2 inch (thick) material. A full sheet of 4 feet by 8 feet by 3/4 inch (thick) plywood would cost $13.44 (32 square feet x $0.42 = $13.44).
Panel products are usually sold in sheets of 4 feet x 8 feet of varying thicknesses.
If a retail dealer quotes you a price per sheet, you can calculate the cost per square foot by dividing by 32 (square feet). Panel products other than plywood include particle board, oriented strand board (OSB), flake board, masonite (tempered and untempered) and fiber board.
Plywood also is classified as structural or decorative. Structural plywood is what most people think of when plywood is mentioned. In a structure (house), it is most frequently used where it is not seen in the finished product. For example, structural plywood may be used as exterior sheathing, subflooring and roof sheathing in a house. In addition to being specified by thickness (1/2 inch, 3/4 inch, etc.), plywood also has varying grades of surface veneers. The grade of surface veneer quality known as "C-D" plywood is probably the most common. The "face" is C quality and has fewer and smaller defects allowed than the "back" of the sheet, which is D quality. Retailers may refer to this condition as "Good-one-side."
Decorative plywood is also called "hardwood plywood" because the "good" side is frequently made from hardwood veneers that give the appearance most buyers prefer. Decorative plywoods are usually thin (1/4 inch) and are used as exposed wall panels or similar decorative applications. Unlike lumber, the dimensions of panel products are not "nominal," but are "actual" or nearly so.
Molding and trim
Molding is always a decorative or finishing product. As a result, it is machined in many irregular cross-sectional contours for particular applications. Most molding is made of soft, uniform, grained wood such as white pine or Ponderosa pine, although hardwood and plastic materials are readily available.
Moldings are usually sold in 10-foot lengths and priced by the linear foot. For example, at $0.36 per foot, a 10-foot piece (or strip) would cost $3.60. A very common application of trim is "base molding" at the juncture of a wall and floor or "window trim" around a window (exterior and interior).
Molding on a window is used for casing, apron and sill, with the baseboard at juncture of a wall and floor.
Thirty or more years ago, floors of most new homes were made of hardwood strip flooring. Today, a high percentage of the floors are wall-to-wall carpeting over plywood subflooring. Possibly the major reason for the change has been the reduced cost. However, the warmth and color possibilities of carpeting also are preferred by many homeowners.
The most widely used hardwood strip flooring is probably a 25/32-inch thick by 2-1/4-inch wide strip. Strips are random lengths, vary from 2 feet to 10 feet or more, and are tongued and grooved as well as matched at the end joints.
Wood strip flooring. Strips are random lengths and are tongued and grooved as well as matched on the end joints.
Strip flooring is sold by the board foot and costs between $1.30 and $1.45 per board foot at this writing (July 1990). To estimate the cost of hardwood strip flooring, measure the length and width of the room to the nearest 3 inches (1/4 foot). Calculate the floor area in square feet. Multiply the floor area by the factor 1.38 to estimate the board feet of strip flooring needed. Multiply the number of board feet by $1.40 (average cost per board foot) to get an estimated cost of the strip flooring. The 1.38 factor includes wastage in installing strip flooring.
For example, a 12-by-15-foot room will require 248 board foot of strip flooring and cost approximately $348:
12 feet x 15 feet x 1.38 = 248
248 x $1.40 = $347.76
The term "bundle foot" may be used at the store. A "bundle foot" is a term used by lumber dealers for purposes of packaging and loading and consists of a unit of strip flooring equivalent to 3 board foot.
An experienced handy-person can install wood strip flooring, but for many homeowners it is probably good advice to consider having the job done by a reputable professional.
Wood block flooring. Thicker blocks usually are tongued and grooved. Thinner ones may be square edged.
Wood block flooring is another product and is available in various forms and sizes. It sometimes is referred to as wood tile, and it comes in squares 4 inches by 4 inches to 9 inches by 9 inches and even larger. Thickness of block flooring varies from 1/4 inch to 25/32 inch.
The thicker blocks usually are tongued and grooved, whereas the thinner ones may be square edged. Many block floors are factory finished and thus require only waxing after installation.
Wood shingles and shakes
Very few wood shingles are used for roofing today; however, possibly 10 percent of the new homes built in Missouri have cedar shakes. Shake roofs are recognized by many home buyers as being desirable from an aesthetic standpoint. Cost and installation is much more expensive than for the more conventional fiber glass or asphalt-based shingles. Wood shingles and shakes are manufactured almost exclusively from western red cedar, a species of wood grown only in the northwestern part of the United States. Shingles are roofing parts sawn to shape, whereas shakes are split from the radius of the log and resawn to give a rustic, irregular top surface and a sawed bottom surface.
The most common shakes are 18 inches or 24 inches in length and are tapered in their long dimension. They vary in width roughly between 4 inches and 12 inches. The variability in width and thickness adds to the random, rustic nature of the finished roof. The exposed butt ends as they lay on the roof are between 3/4 inch and 1-1/2 inches thick.
Shakes are sold in factory-strapped bundles and are labeled to prescribe the number of bundles required to cover a "square" or 100 square feet of roof. For example, about seven bundles of 18-inch shakes will cover a square of roof provided the "exposure" is 7 inches of the shake length. (Exposure is long dimension of the visible part of the shake.) About five bundles of 24-inch shakes will cover a square, with exposure of 9 inches. In short, as the exposure increases, the number of bundles required to cover a square decreases.
Cedar shakes. "Exposure" is long dimension of visible portion of shake.
Shake roofs may require some maintenance every other year or so for best results. On the north or shaded side of a roof, moss can be a problem and should be removed routinely to prevent decay of the shingles. If a house has overhanging tree limbs, debris from the tree — bark, twigs, acorns and leaves — can become lodged between the shingles and should be removed every year or so. If a roof is not steep, it should be swept with a stiff-bristled broom in late fall each year.
Wood posts are sold in three different shapes — round, half round or square. They are sold by length (even foot increments) and by diameter (inches), measured at the small end in the case of round and half round. The "small end" is the top of the post as it grows in a tree. An 8-foot-long full round post 7 inches in diameter at the small end would be specified as "7 inches by 8 feet round." An 8-foot-long half round post, 5 inches in diameter at the small end would read "5 inches by 8 feet sawn halve."
Wood post. Sold by length and diameter, measured at the small end in the case of round and half round.
Cordwood is irregular chunk fuel and may be somewhat difficult to handle and measure. The only legal fuel wood measure in Missouri is the cord — 128 cubic feet of wood tightly and closely stacked. Firewood is often sold by a vaguely defined measure rather than a clearly defined volume understood by both buyer and seller. For example, a seller may sell his wood by the pickup load, rick, rank or face cord. But these measures are inadequate because they can vary by definition from one location to another. Wood delivered to the buyer should be stacked as prescribed above and "measured" by the buyer before it is dumped at the delivery site.
Cordwood pile. Wood should be measurable so "cords" can be determined.
The cords in any rectangular pile can be calculated by measuring the length (L), width (W) and height (H) in feet and using the following formula:
||L (feet) x W (feet) x H (feet)
For example, a rectangular pile 10 feet long by 3 feet wide by 4-3/4 feet high will contain 1.1 cords.
||10 x 3 x 4-3/4
|= 1.1 cords
G5506, reviewed October 1993