R E - D R I E D T R E AT E D L U M B E R LIGHTER, CLEANER, ENVIRONMENTALLY SOUND
Foreword The purpose of this booklet is to assist you in getting more value, performance, and satisfaction from pressure-treated lumber. Since the earliest days of our country, Americans have built their homes of wood. Even after the passage of centuries, lumber is still our most popular building material. Now, pressure-treated lumber provides architects, designers, and builders with bold new options when formulating construction plans. New pressure-treating technology has greatly extended the range of safe, dependable usage for lumber. No longer inhibited by hazards such as decay and termites, architects, engineers, designers and builders are giving free rein to their imagination in wood design and construction. The advantages of wood s inherent properties strength, versatility, ease of fabrication, resiliency, resistance to wear, warmth and economy can be utilized in most structures under conditions of severe weather exposure. Wood is our only renewable natural resource and by pressure-treatment, one tree will last for a period that would require the use of ten untreated trees. This is true conservation. We enjoy the prolonged use of the wood while conserving our forests as well. Architects, contractors, lumber dealers, building officials and especially home builders will find the information contained in this booklet useful.
Southern Pine... The Raw Material DRY Pressure-Treated Lumber Has Greater Strength The United States is blessed with a remarkable building material, Southern Yellow Pine. United States Department of Agriculture tables show that properly DRY Southern Pine is among the strongest of all woods and is the wood with the greatest nail and bolt holding power. Pound for pound, clear, DRY Southern Pine is stronger than steel. In fact, it is known as the Supreme Structural Wood of the World. As a bonus, the sapwood of DRY Southern Pine treats very readily with a modern EPA registered preservative, making it decay and termite resistant for decades. When treated Southern Pine comes from the treating cylinder, the wood fibers are saturated with excess water. Thus it does not emerge as a finished product; another essential step is required to make it ready for consumer use. That process is the re-drying of the lumber after treatment and before it is used.
Re-drying After Treatment... Vitally Important One of the authorities on building standards in the United States is the Federal Government s Forest Products Laboratory. The Laboratory scientists say it is vitally important to use only lumber that is properly seasoned (that is, redried after treatment to an average moisture content of 19% or less). The benefits are numerous for pressure-treated wood that is re-dried after treatment: Dry Pressure-Treated Lumber minimizes shrinkage problems. Dry Pressure-Treated Lumber has greater strength and stiffness. Dry Pressure-Treated Lumber is more uniform in size. Dry Pressure-Treated Lumber has better nail and bolt holding power. Dry Pressure-Treated Lumber is safer. Dry Pressure-Treated Lumber is cleaner and lighter. Dry Pressure-Treated Lumber can be easily painted, stained, water repellant coated, or left to weather to a natural driftwood gray. Dry Pressure-Treated Lumber meets building codes, FHA, and grade stamp requirements.
Simple Rules to Follow When Buying Pressure- Treated Lumber Quality-Conscious Builders Use Only DRY Pressure-Treated Lumber Take the guesswork out of buying pressuretreated lumber by adding proper moisture content provisions to your purchase specifications. When the moisture content of pressure-treated lumber is not specified, the buyer has no assurance that the lumber purchased will be satisfactory for its intended purpose. The following specifications can be used as a guide: * Each piece of Southern Pine lumber shall comply with the American Softwood Lumber Standard PS 20-70, and the Southern Pine Inspection Bureau grading rules. Each piece of lumber shall bear the grade mark of a recognized agency or independent inspection service certified by the Board of Review, American Lumber Standards Committee. In addition, all treated Southern Pine shall conform to the approved standards of the American Wood-Preservers Association. Each piece shall be treated in accordance with AWPA standards and certified by an approved inspection agency. All lumber, 2 or less in thickness, treated with waterborne preservatives should be re-dried after treatment to an average moisture content of 19% or less. For the lumber grademark to be valid after treatment the lumber must adhere to the grade requirements and the moisture content of the grade represented by that mark. Proper re-drying after treatment is a protection that rightfully belongs to every builder or home owner. You should insist on it always. * Pressure-Treated Southern Pine by Southern Forest Products Association, 3/87
DRY Pressure-Treated Lumber Minimizes Most Shrinkage Problems Wood technologists tell us that the fiber saturation level of wood is reached when it holds a moisture content of about 28%. They also point out that wood shrinks approximately 1% for every 4 percentage points below the 28% level. To insure maximum satisfaction then, the lumber should be dried or pre-shrunk before installation. Changing conditions such as rain, temperature, sun, shade, and relative humidity will all affect the moisture content of wood. Thus, some changes in its size can be expected. Experience has shown that lumber dried to 19% moisture content, installed outdoors, will undergo limited dimensional changes. Warpage, another result of lumber shrinkage, is also minimized when the wood has been properly dried prior to installation. All lumber shrinks as it dries. The place for this shrinkage to occur is under controlled conditions at the treating plant, not after it is erected in a home or other structure.
DRY Pressure-Treated Lumber Is Safe, Light & Clean Today with the heightened concerns about the potential hazards of chemicals, there are two things that should be considered when specifying or purchasing pressure-treated wood: 1) that it is safe, and 2) that it works. DRY Pressure-Treated Lumber is Easier to Handle The re-drying of pressure-treated lumber is the only way to insure immediate and complete fixation of the preservatives within the wood cells, providing a safe, clean, and durable building material. The excess moisture resulting from the treating process adds appreciably to the weight of the lumber. This added weight increases handling costs for the supplier and the builder throughout the construction process. Properly re-dried pressure-treated lumber is the type of wood that carpenters and other workers prefer to handle, cut, and install on any project. To satisfactorily accept paint, stain, or a coat of water repellant sealer, pressure-treated lumber must be re-dried properly to assure the necessary penetration and adhesion. Moisture trapped inside improperly re-dried wood is the most common cause of paint blistering and peeling. Always follow the paint manufacturer s recommendations.
FHA & Building Codes Require or Specify DRY Pressure-Treated Lumber The Federal Housing Administration, the North Carolina State Building Code, the Standard Building Code and the Uniform Building Code all require that pressure-treated lumber two inches or less in thickness contain not more than 19% moisture content at the time of installation. Most architects specify that pressure-treated lumber be re-dried to assure satisfactory performance in their projects. The Southern Pine Inspection Bureau grading rules for untreated Southern Pine include moisture content limits for all grades of lumber. Dryness or seasoning of Southern Pine is a standard grade requirement. (This is expressed as maximum moisture content under paragraphs 160-168 of the Southern Pine Inspection Bureau Grade Rules.) The grade mark is an identification of the grade, seasoning and producer. Once graded and grade marked, Southern Pine that is then treated with waterborne preservatives has its grade mark invalidated. In this wet state, pressure-treated lumber would no longer meet the seasoning requirements established for untreated lumber. It is obvious that these authorities regard the proper re-drying of pressure-treated lumber as important.
DRY Pressure-Treated Lumber Has Better Nail Holding Power DRY Pressure-Treated Lumber Insures The Integrity of Your Project Nails are critical to the structural integrity of a building as they hold together the principal parts of its framework. Driven into DRY pressuretreated lumber, nails hold tight and stay tight. With lumber that has not been re-dried after treatment, the drying that occurs after it is installed causes it to shrink, thus loosening and weakening joints. A substantial part of the nails holding power is lost. The United States Bureau of Standards and the U.S. Forest Products Laboratory report that this loss can be as much as 75%. Corrosion If a piece of wood with a nail in it is placed outside, temperature changes, water, oxygen and other elements in the environment will promote the corrosion of metal fasteners. For this reason hot-dipped galvanized or stainless hardware is recommended. Many fastener and hardware companies who have tested with the new alternative preservatives suggest that minimum standards for hot-dipped fasteners should meet ASTM A 153, and for connectors ASTM A 653, class G-185.
Dealer Name Dealer Address Dealer City, State Zip Dealer Phone Number Dealer Fax Number Industries, Inc. P.O. Box 1124 Orangeburg, SC 29116 (800) 476-4401 www.coxwood.com 2008 DUR-02