Press Release
For Year-Round Time Frame
UNIVERSITY PARK, Pa. -- Many a homeowner can stride into a lumberyard or home store and announce the need for a 2-by-4 board. Very few consumers, however, will know what kind of 2-by-4 to ask for, says a wood products expert in Penn State's College of Agricultural Sciences.
Everything you always wanted to know about finish, framing and composite woods is printed on what is called a "grade stamp" on every board sold in the United States, according to Roy Adams, associate professor of wood products in the School of Forest Resources.
"There is an incredible amount of information contained within a stamp no bigger than a cocktail napkin," Adams says. "Professional contractors and lumber experts know what to look for, but average homeowners shopping for do-it-yourself projects can buy the wrong thing if they're not careful."
Wood has served as a structural material since King Solomon called for a temple to be built from the cedars of Lebanon. Standardized lumber came into use in the 19th century, as lumber became cheap and modern house framing developed. Eventually, lumber manufacturer associations established standards for their members, and in 1924 the Department of Commerce standardized lumber grades throughout the United States.
"The idea behind lumber grading is consistency of product quality and strength standards," Adams says. "Also, in case of liability, lumber grade stamps can show investigators where the product came from."
For the consumer market, homeowners should familiarize themselves with grade stamps for softwood lumber, long used in the construction industry, and composite wood products such as plywood and oriented strandboard. "Hardwoods such as oak, maple and cherry have grade stamps as well," Adams explains. "However, these grades are geared toward the appearance of the wood for finish carpenters or furniture makers. The average homeowner wouldn't be using this type of lumber."
For structural lumber, Adams says there are three elements every do-it-yourselfer should check on the grade stamp.
--Moisture content. There are two moisture grades, printed on stamps as "S-Dry," which means the board has less than 19 percent water weight, and "S-Grn" (for green), which means the board has more than 19 percent water weight. "If you buy green lumber or dry lumber that has been left out in the weather, try to buy and store it ahead of time so the wood can lose moisture," Adams says. "If you use wet wood in a project, the lumber will shrink causing unsightly gaps or squeaky floors."
--Species. Lumber associations have grouped many different softwood species into stamp categories that can contain one species or many. The most common in the northeastern United States are: Southern Pine, Spruce-Pine-Fir, Douglas Fir, or Hem-Fir. "Homeowners must know the species category because each one has different strength and structural properties," Adams says.
--Lumber Grade. There are many different types of lumber grades, most aimed at the construction industry. Adams explains that most homeowners will see just four grades: Select Structural (SEL STR), No. 1, No. 2 and No. 3. "Select structural is nearly knot-free and, as a result, is rare and very expensive," Adams explains. "You would use select grades only if appearance were important. Grades 1 through 3 are graded on how many knots appear in the board and how that affects the strength of the lumber."
Adams says that composite wood products, such as plywood and oriented strandboard, also carry grade stamps. Plywood is made by removing thin sheets of wood called veneers, which are glued together to form a solid sheet. Oriented strandboard uses thin strands of wood that are glued and compressed into a solid panel. Both products usually are sold in 4-by-8 panels.
The stamp will identify the product and also lists an exposure rating. The exposure ratings are: Exposure 1, Exposure 2 and Exterior. "As its name implies, only the exterior grade should be used where it will be exposed to the weather," Adams says. "Panel products are made with waterproof adhesives, but repeated exposure to water will cause deterioration. A good rule of thumb is to paint or seal any panel product if it is outdoors."
Adams points out that most home centers have knowledgeable sales staff that can recommend lumber for projects. He adds that a working knowledge of grade stamps will allow the consumer to check the quality and strength of materials without the help of a clerk or a contractor.
________________________________________________________________________
To contact Roy Adams, please call (814) 863-2976.
Editor: John Wall
Phone: 814-863-2719 office
Email: jtw3@psu.edu
PR #02128
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