Wood is a natural renewable resource that requires far less energy to produce than man-made products such as steel or plastic. Pressure treatment, with preservatives, substantially extends the life of wood products exposed to the weather and particularly beyond that of the natural durability of the wood we now harvest. More and more wood is being cut from, second growth (replanted) softwood with little durability. Therefore, preservatives are a necessity.

Chromated Copper Arsenate (CCA) has been the chemical used by pressure treated lumber manufacturers. In Canada, this preservative is fixed to the cells of the wood by the use of fixation chambers. In the United States, the southern yellow pine treaters do not have these fixation chambers and do not wish to spend the additional capital and operational costs to acquire them. Therefore, the treated lumber often found in the U.S. has not been fixated and is more likely to leach into the soil.

The next generation in wood preservation is Alkaline Copper Quat (ACQ). This preservative does not require the use of fixation chambers. The North American chemical suppliers to the pressure treating manufacturers are voluntarily changing from CCA to ACQ by the end of December 2003.

The color of ACQ pressure treated lumber is a much darker green than CCA treated lumber and when it is exposed to the elements it will initially weather to a natural brown color and eventually will turn grey following long-term exposure to the sun.

ACQ treated lumber will_be more expensive due to the increased cost of the chemicals used in its manufacture. ACQ also has very different treatment characteristics that require proper hardware to be used in conjunction with its installation.

The testing that has been done to date indicates that ACQ is somewhat more corrosive than CCA. The treated wood industry recommends the use of stainless steel and hot-dip galvanized connectors and fasteners with all treated wood. Electro-plated finishes are not recommended for use. The joist hangers that Greentree has chosen for use on ACQ treated lumber have a heavier/thicker coating than the standard hot-dip galvanized coating. Due to this increased galvanized thickness these connectors are expected to have a longer service life. These 18 gauge joist hangers have the highest loads of any face mount hanger. The hangers have double sheer nailing for greater strength and use less nails for faster installation. Hot-dip galvanized nails must be used with these hangers.

For the best results, fasteners recommended for use with ACQ treated wood and approved by the building codes should be used. We have chosen one such fastener which has a zinc and polymer anti-corrosive coating and is a good color match for the color changes ACQ goes through. This exterior all-weather screw provides superior protection from rust and corrosion and withstands destructive elements like chemicals, acid rain, sunlight, saltwater and industrial pollutants. Designed specifically for exterior decks, these construction screws go in fast and hold tight. They have a ribbed head for easy seating in lumber and a #2 Robertson drive.

We have purchased some hot-dip galvanized lag screws and washers and also some separate washers for use with wedge anchor bolts. We will also have some skew-able angles that will match joist hangers. All of these are for use with ACQ treated lumber.

It is notable that preserved wood foundation material (PWF) is not available in ACQ but will continue to be made available in CCA.

The fundamental safety of CCA treated wood has not changed, but perceptions in the marketplace have. The preserved wood industry stands by the safety of all wood products treated with CCA which has been used for nearly 70 years. Manufacturers have made a decision to be responsive to customer interest in new preservatives that provide the same benefits of CCA treated wood. The time is right now because the industry has developed this new generation of preservatives and can begin the transition.

Remember this: Preservatives make and keep wood products sturdy.

 Remember this: Preservatives make and keep wood products sturdy