KDAT Lumber FAQS

KDAT (Kiln Dried After Treatment) wood can provide many advantages as a choice for wood fencing. Because wood is porous, it is ideal for the pressure treating process, but it also has a natural tendency to warp, cup, twist, crack, check, shrink and swell as it is exposed to wetting and drying cycles involved. While the preservative is left in the wood for protection, the water is released as the wood naturally dries, bringing out these natural tendencies which cause problems when using it in fence construction.

The KDAT process removes the excess moisture from wood that is introduced by the treatment process, improving the performance and stability of pressure treated wood. Northern Crossarm Co., Inc., specializes in treated lumber and their team provided answers to some frequently asked questions about KDAT.

What’s Involved in the Traditional Pressure Treating Process?

Pressure-treated wood is immersed in a liquid preservative (commonly chemicals) and placed inside of a pressure chamber. Once inside the pressure chamber, the chemical preservative is forced into the wood fibers, effectively penetrating to the core of each piece of wood. Common pressure treating chemicals used today are ACQ (alkaline copper quat) and MCA (micronized copper azole). In the past, chromated copper arsenate (CCA) was used, but has since been restricted in residential settings due to the health and environmental concerns. ACQ, (alkaline coper quat) is a commonly used alternated to CCA. MCA is a greener treating chemical whose use has been expanding in recent years. Extremely versatile, MCA can be used in Above Ground, Ground Contact and Freshwater Contact applications. It’s a copper-based wood preservative and provides long-term protection of wood exposed in exterior applications.

How is the KDAT Pressure Treated Wood Process Different?

KDAT wood is treated similarly to “green” or “wet” wood with one key difference. After KDAT wood has been pressurized with chemicals, it goes through an extra drying step in a kiln. Using controlled temperatures, the lumber is stacked to provide airflow between each board and to ensure uniform drying. Traditional “wet” or “green” lumber that doesn’t undergo this process will take as long as eight months to a year to dry out, often resulting in problems with warps, cups, checks and shrinking over time. Once in the kiln, the moisture is reduced by as much as 80% to create a much drier piece of wood and minimizing those potential problems.

What are the Recommended Applications for KDAT Wood?

• Deck Boards,

Deck Rails & Deck

Substructure (Joists, Posts) • Pergolas • Fencing • Boardwalks, marine construction • Flatbed trailers • Storage sheds

What Benefits Does KDAT Lumber Offer?

• Lighter, easier to handle • Can be painted, stained, or sealed immediately • Even drying minimizes cups, warps, checks and shrinks • Easier to saw, drill and plane • Better holding power for nails and screws

What Wood Species & Sizes of KDAT Lumber are Available?

Southern Yellow Pine – Also referred to as SYP.

SYP is strong, stiff and yield a high proportion of sapwood which is ideal for absorbing preservative and chemicals.

Douglas Fir – Extremely strong and less prone to warps and splits (other than Southern Yellow

Pine), this wood is predominantly found in the

Western United States and Canada.

Red and Ponderosa Pine – Not as strong as

Douglas Fir or Southern Yellow pine, but still good at absorbing preservatives. Found in the

Northern United States and Canada.

Regarding sizes, KDAT wood is usually available as dimensional stock for rail components (2x4s, 2x6s, 4x4s, 6x6s and 2x2s). For decking, KDAT wood is typically available in 5/4x6s and 2x6s. And finally, for joists, stringers and beams, KDAT treated wood is commonly found in 2x8s, 2x10s and 2x12s.

FAQsKDAT Lumber

What Should Not be Expected from KDAT Lumber?

Strict Uniformity. Sawn lumber will vary in dimensional size due to mill inconsistencies. KDAT can only restore lumber sizes close to their original size. IT IS NOT EXACT. Exact Moisture Content. With KDAT lumber, a moisture range of (125%-19%) is targeted. KDAT is not an exact science, and lumber will have variations in moisture content. Moisture variations will become considerable if the lumber is exposed to moisture after the KDAT process.

Elimination of All Natural Characteristics.

While KDAT improves the performance of treated lumber, it cannot eliminate these natural characteristics completely. Some warp, cup, twist, check, crack, shrink and swell is to be expected with any wood.

What is the Typical Maintenance Required for KDAT Lumber?

KDAT wood will need to be sanded, cleaned and stained every two to five years. However, because a large percentage of moisture is removed from the wood prior to construction, boards are normally returned to as close to their dimensional size, leaving a product that is longer lasting and easier to maintain. For more information about the KDAT process and products, visit www.crossarm.com.