Tenino copper naphthenate (2% as metal) meets the requirements set forth in AWPA M4 Standard. Copper naphthenate is available at many building supply and hardware stores or online at Amazon.com.

The appropriateness of the preservation system for field treatment shall be determined by the type of preservative originally used to protect the product and the availability of a field treatment preservative. Because many preservative products are not packaged and labeled for use by the general public, a system different from the original treatment may need to be utilized for field treatment. Users shall carefully read and follow the instructions and precautions listed on the product label when using these materials. Copper Naphthenate preservatives containing a minimum of 2.0% copper metal are recommended for material originally treated with copper naphthenate, pentachlorophenol, creosote, creosote solution or waterborne preservatives.

Tenino Copper Napthenate (2% copper as metal) protects the end-cut of the 2x6 pressure treated pine board

Tenino Copper Naphthenate contains 2% (as metal) Copper Naphthenate in oil. This ready-to-use solution is conveniently packaged in both pints, and gallons. Tenino is ready-to-use requiring no mixing or dilution. It can be applied by brush, or dip. Use it for end-cut protection on treated wood. Tenino conforms to AWPA Standard M-4, Section 7.1.1. requirements. By law: Always apply Tenino Copper Naphthenate in a manner consistent with the label.

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Tenino Copper Naphthenate

Is Non-Corrosive to Hardware and Fasteners.

In corrosion studies Tenino demonstrates no excessive corrosion of hardware and fasteners due to contact with the preservative.

Copper is both repellent and toxic to termites. The University of Hawaii has found Copper Naphthenate in wood at loadings of 1.5 lbs. per cubic foot is resistant to Formosan Termite attack and degradation. Tenino will successfully protect against termites only if minimum loadings and sufficient penetration are achieved. Tenino is best used to supplement pressure-treated preservative wood protection in aggressive hazard class environments envisioned in AWPA Use Category 4, 4B,4C.


Copper Naphthenate has been used as a wood preservative for over one hundred years with many applications for use including; field boxes, benches, flats, fence posts, canvas, burlap, ropes, nets, greenhouses, utility poles, crossarms, and wooden structures in ground contact and above ground contact. The American Wood Protection Association's (AWPA) standardization process has confirmed oil-borne copper naphthenate's efficacy as a wood preservative. The USDA Forest Service Forest Products Laboratory has documented in field trials copper naphthenate's long-term protection performance.

End-cuts of pressure treated lumber field-treated with Tenino Copper Naphthenate


Copper Care Wood Preservatives, Inc. formulates Tenino Copper Naphthenate with low VOC oils to comply with the South Coast Air Quality Management District's (SCAQMD) Rule 1113, and ICC 700 National Green Building Standard (NGBS) with less than 350 VOC grams per liter. Tenino is 100% domestically sourced from recycled copper and reclaimed by-products.

Tenino For Building Code Compliance

"Field-cut ends, notches and drilled holes of preservative-treated wood shall be treated in the field in accordance with AWPA M4"

R317.1.1 2018 International Residential Code (IRC)

Preservative-treated wood "Lumber, timber, plywood, piles and poles supporting permanent structures required by Section 2304.12 to be preservative treated shall conform to the requirements of the applicable AWPA U1 and M4 for the species, product, preservative and end use."

2303.1.9 2018 International Building Code (IBC

"Lumber, timber and decking used in structural applications shall be field treated in accordance with Section 6.1 when cut or drilled during construction."

Section 6.2 2019 AWPA M4 Standard

"Copper Naphthenate preservatives containing a minimum of 2.0% copper metal"

Section 7.1.1 2019 AWPA M4 Standard

Always use Tenino Copper Naphthenate (2% as metal) when treating cuts to satisfy AWPA Standard M4. And comply with building codes.

For more information about AWPA M4-15 standard visit the AWPA website, or purchase the 2020 AWPA Book of Standards.

Treated Wood Warranty Protection

Pressure treated such as MicroPro, LifeWood, EcoLife, AC2, Wolmanized, EraWood and others have warranties which exclude coverage when cuts, holes, etc. are not field treated with a brush on end cut solution during construction. Each warranty's language differs (see specific products warranty for exact language), in most instances Tenino Copper Naphthenate with 2% metallic copper fulfills the warranty exclusion clause for field treatment. If your lumberyard or building supply store doesn't carry Tenino 2% Copper Naphthenate, protect your investment and demand Tenino whenever you use pressure treated wood or lumber with a limited warranty.

Broad Use and Safer Handling

Copper Naphthenate provides protection against wood decay and the superior water repellent qualities of an oil borne wood preservative. Copper Naphthenate treatments result in wood that is cleaner to the touch, with minimal excess preservative coming in contact with the environment. Copper Naphthenate is the green choice in preservatives because it is not a restricted use pesticide. With durability equal to or better than other preservatives, it is a great choice for bridge timbers, barn timbers, glulam beams, salt storage domes, protector boards and highway railings. For many applications copper naphthenate is the best wood preservative available to contractors and builders. Use copper naphthenate when wood will be in contact with the ground and as an an end-cut treatment for pressure-treated wood.