Image of inspectors examining treated timber cores.

Jimmy Williams of MDA and Todd Greer of Timber Products Inspection (TP) examine cores taken from several bundles of penta treated fence posts that were purchased by a Missouri dealer.

One significant responsibility of the Missouri Department of Agriculture’s Treated Timber Program is the regulation of the wood treating industry. This regulation deals with the quality of treated products produced and is conducted by the authority of the Missouri Treated Timber Law.

Inspections are conducted at wood treating facilities and retail / wholesale business that sell treated wood products to ensure that proper treating methods are being followed. In addition, core samples of the finished product are taken and analyzed to determine depth of penetration and net retention. Depth of penetration refers to how deep the wood preservative had actually gone into the wood. Net retention refers to the actual quantity of chemical found in the wood.

2016 Treated Timber Summary Report

Missouri is home to a variety of wood treating facilities. MCA, ACQ, Creosote, Pentachlorophenol and Copper Naphthenate are examples of wood preservatives being used to treat wood products here in Missouri. There are also a variety of newer wood preservatives entering the Missouri market from out-of-state wood treaters.

Image of treated timber cores.

Cores taken from penta treated fence posts (Southern-Yellow Pine) that were sprayed with heartwood indicator and “penta check.”

In addition to monitoring the quality of Missouri’s treated wood products, the program also issues two types of licenses. Producer licenses are issued to wood treating facilities in-state and out-of-state that both treat and sell wood products into Missouri. Dealer licenses are issued to retail and wholesale businesses (or establishments) that only SELL treated wood products in Missouri.

Complete list of approved wood preservatives currently being sold in Missouri

For additional information regarding the rules and regulations associated with the Missouri Treated Timber Law or to view licensed treated timber producers or dealers, please refer to the following websites:

Businesses that wish to obtain a Missouri Treated Timber Producer License may download the following Missouri Treated Timber Producer License Application and Treating Statement:

Treated timber dealers may now purchase a new license or renew established treated timber dealer licenses online.


Download the following Missouri Treated Timber Dealer License Application and submit check by mail.

For additional information on treated wood products, see the website below:

For further information contact the Bureau of Feed, Seed and Treated Timber.