Some Of The Most Frequently Asked Questions About Treated Lumber

ACQ Pressure-Treated Lumber

Answers to common questions about pressure-treated lumber.
ACQ Pressure-Treated Lumber; A Wood Preservation Lumber's greatest enemy is biological attack ,destruction by termites, fungi, marine borers and bacteria. After more than a half century of scientific tests and practical experience with various treating chemicals, there is a variety of weapons that have been formulated to protect wood against insects, rot and decay.

What preservatives are used and how long are they effective?

For a long time, CCA (Chromated Copper Arsenate) has been used as a reliable wood preservative. CCA treated wood protects against all major forms of destructive attack and is effective for up to 50 years. More recently, preservative manufacturers have made a transition to a newer preservative: ACQ (Alkaline Copper Quaternary.) ACQ is also effective for up to 50 years, reducing demands on forest resources.

What ingredients make up ACQ?

ACQ is a waterborne system that is copper-based. The copper and quaternary compounds together provide protection from a broad spectrum of fungi and termites, preventing rot and decay.

Is special handling required?

Although termites, fungus and destructive micro-organisms detest treating chemicals, in pressure-treated wood it's clean, emits NO fumes and is non-irritating.

The single most important precaution is DO NOT BURN TREATED WOOD. Burning treated wood releases the chemical bond with wood cells, so dispose of scraps and sawdust with your landfill trash. Wear gloves when handling treated lumber. And always wear safety glasses and a dust mask when sawing or cutting treated lumber just as you would with untreated lumber.

How safe is treated wood?

Very safe when used as directed. The preservative injected into lumber reacts with the wood substance to form an insoluble complex. It won't evaporate or vaporize. Treated wood is clean, odorless, non-staining, and safe to work with and handle. Its locked-in protection is non-irritating to children, adults, animals and plants. The minute amounts of preservative released over time due to wear off of the product or water contact have been carefully studied. The conclusion is clear: it is safe for the environment and safe for people and pets.

Can preserved wood be used indoors?

Treated wood may be used indoors for any application except cutting boards and countertops.

Why can treated wood be used for a picnic table and not a countertop?

Simply because picnic tables are primarily used for serving prepared food while a kitchen countertop is used primarily as a cutting surface for raw food.

Can treated wood be used in gardening?

Yes. Treated wood can be used to construct raised vegetable gardens and flowerbeds. Previously, CCA (Chromated Copper Arsenate) had been used as a reliable wood preservative. More recently, treated wood manufacturers have made a transition to a newer preservative: ACQ (Alkaline Copper Quaternary.) Several studies have shown that plants grown in CCA raised beds do not contain higher than normal levels of the preservative chemicals. It is believed also that the same holds true for ACQ raised beds. In addition, the components of ACQ are known to be non-carcinogenic.

Can all tree species be treated?

Three species of pine: southern yellow, ponderosa and red are most open to treating. Some softwoods such as spruces, hem/fir, larches and Douglas fir benefit from incising (cutting small slits across the grain) to aid chemical penetration and treatment retention. Most hardwoods are too dense and complex to be treatable.

What does PCF Treatment mean?

Treatment levels are measured in pounds of chemical injected per cubic foot (pcf) of wood. Additionally, lumber tags will always state above ground only (.25 retention) or ground contact (.40 retention) so you can be sure you are using the right material for the job. Higher levels of retention are available for special purposes such as extensive moisture/earthen contact - e.g. in foundations, pole barns, fresh & saltwater docks, culverts, etc.

Any suggestions when building with treated lumber?

One quite important one: Use hot-dip galvanized (meeting ASTM-A153/A653) or (304 or 316) stainless steel nails or screws, otherwise, your treated wood will last longer than the unprotected fasteners you've used to put it together. Do not use preserved wood in direct contact with aluminum. A poly barrier is recommended for any applications where treated lumber will meet aluminum flashing. Aside from that precaution, you can saw it, sand it, or glue it just like any ordinary wood.

After my project is built, is any special maintenance necessary?

Left unfinished, treated wood ages gracefully, eventually softening to an attractive driftwood gray. On flat surfaces such as decks, however, leaves and other debris may collect and create unsightly stains. Even if your lumber has the locked-in protection of factory applied water repellent, you'll want to follow an annual program that includes a semi-transparent stain of a sealant which contains an ultraviolet stabilizer. If you stain your project, a quality penetrating latex or oil base stain is recommended.

What else should I know about treated wood?

Decades of research and testing have gone into its development, and we certainly haven't answered every question about it. However, a full line of free literature is available to you through your building materials dealer. Finally, you should be aware of this: lengthening a wood structure';s life through pressure treatment lowers the pressure on our planet's exhaustible mineral and energy resources. 226,000,000 trees are saved every year by pressure treatment. Treated lumber makes one tree last as long as many untreated trees. Use pressure-treated wood with confidence in its everlasting quality and safety. You'll be protecting our environment's major renewable building material.

I cut the end off of my ACQ treated wood, and it looks like it isn't treated in the middle. Do I have a bad piece of treated wood?

No. Products treated in strict conformance with AWPA standards will have some wood which appears untreated if the wood is end-cut after treatment. Most commonly, this is heartwood which is naturally decay resistant. This is not an indication that the wood was not properly treated, and you do not need to be concerned. With the exception of some Western species, these end-cuts do not require any special treatment.

Brush-on Preservatives for Field Cuts

According to American Wood-Preservers' Standard M4-02, lumber and timber which are used in above ground applications and are of sapwood species such as southern, red or ponderosa pine, generally do not require treatment to provide a good service life. Other heartwood species, typically found in the Western US, should be field treated when cut or drilled. If you are concerned about wood exposed due to cutting or drilling, you can use a brush-applied preservative. Home centers and lumberyards often carry brush-applied preservative systems based on two different active chemicals: either copper naphthenate or IPBC (3-iodo 2-propynyl butyl carbamate). These systems should be applied, in accordance with their labels, to any surface exposed by damage or field fabrication. Users should carefully read and follow the instructions and precautions listed on the preservative system label when using them.