PtW PK

PLUGS IN your pressure-treated wood? That’s typically a good sign.

QUALITY MARK gives assurance that the wood has been inspected by an accredited third-party agency.

Digging into plugged holes in treated wood

As a buyer of pressure-treated wood products receiving your order or while shopping for items in the store, you may be surprised to see pieces containing plugged holes. If you are like most consumers, you may think, “That can’t be good!” On the contrary, it can be a good thing, and here’s why!

Like all manufactured products, various quality control practices determine if pressure-treated wood products meet the specified minimum quality standards. To meet building code specifications; treated wood products must conform to industry quality requirements. These requirements are checked by the producing treating plant, and then the plant’s quality control process is audited by independent, third-party agencies that ensure plants produce treated wood products in accordance with industry standards. Finding these plugged holes in pieces of treated lumber is evidence that this quality system is in place.

The American Wood Protection Association’s (AWPA) Book of Standards provides the minimum specifications and practices for evaluating preserved wood. Most model building codes, including the International Building Code, will specify AWPA Standards, or equivalent, as minimum acceptance criteria. The industry standards used to evaluate the level of treatment in wood products require a sampling process.

The AWPA quality control measures used to evaluate the level of treatment in lumber products requires that the plant utilize a sampling process that includes collecting wood borings randomly from a minimum number of pieces within a given treatment batch or “charge.” These cores are taken by a special boring bit that cuts and removes a predetermined length core. The core sample is then observed to determine the depth of preservative penetration and the analysis of preservative retention in a specified, outer assay zone.

The treating plant is responsible for applying this process on every charge of wood that it treats. The minimum preservative penetration and retention requirements must be met before a charge is considered conforming and

SPECIAL BITS cut and remove borings from randomly selected pieces of just-treated wood. The borings can then be analyzed to determine the depth of preservative penetration and extent of retention.

released for shipment. Before shipment, however, the resulting boring holes used in the evaluation process must be filled with tight-fitting treated wood plugs to prevent easy access by insects or decay fungi once in service. While these boring holes may appear a bit unsightly, they do not negatively impact the structural integrity or usability of the sampled piece.

Charges documented as conforming for preservative penetration and retention by the treating plant are subject to further sampling by accredited third-party inspection agencies as they audit the effectiveness of in-plant quality control procedures. The third-party inspection audit process includes the same sampling process, creating additional plugged pieces of wood.

Under an accredited third-party quality audit program, plants in good standing may use the agency’s quality mark. Be sure to always look for these quality marks to find important information about your preserved wood products.

Now that you understand how pressure treated wood products are evaluated, you will hopefully view the resulting plugged holes as reassurance that your product has been inspected and found conforming to industry standards. Enjoy your treated wood products with confidence!

– Kim Merritt is director of the treated division of Southern Pine Inspection Bureau. For more information, please visit www.spib.org.

• Full Service Pressure Treated Lumber & Plywood • Cedar Deck Accessories • Specialty Decking Products

Tacoma, WA 800-426-8430