Is Your Deck built with Alkaline Copper Quat Pressure Treated Lumber?

August 9, 2004

Recently, we’ve been made aware of a few concerns, stemming largely from the United States, regarding decks that were built with Alkaline Copper Quat (ACQ) pressure treated lumber and where improper joist hangers and fasteners were used. In some cases, individuals have reported that the ACQ pressure treated lumber reacted with standard joist hangers and fasteners causing unexpected corrosion of the fasteners and joist hangers weakening the structural support of the deck.

If you are considering using ACQ pressure treated lumber when building your deck, there are a few things that you should know:

· Make sure that you use only hot-dip galvanized joist hanger nails to secure appropriate joist hangers, such as the Simpson Strong-Tie ZMAX G185 joist hanger. The ZMAX hangers have a heavier and thicker galvanized coating than the standard hangers. Due to this increased galvanized thickness, these products would be expected to have a longer service life than standard galvanized products. As a matter of fact, this product was designed specifically for use with ACQ pressure treated lumber. Make sure to only use hot dip galvanized fasteners and fittings.

· Ensure that the ACQ pressure treated lumber is at least ¼” away from any aluminum flashing.

· Use only hot-dip galvanized lag bolts and washers, which are used to attach the joist hangers. Also, only use hot-dip galvanized bolts for posts, nails, joist hangers and joist hanger nails, and any other fasteners used in the construction of the deck.

· Only use screws made for use with ACQ pressure treated lumber.

If you have already constructed your deck using ACQ pressure treated lumber, and did not use hot-dip galvanized fasteners and joist hangers, you will probably want to inspect your hangers and hardware to check for any excessive corrosion. If you find that corrosion is present, you may be required to replace the hangers and hardware.

This will be a tedious job and you will be replacing the joist hangers and any other fasteners one at a time. Make sure to use products such as the Simpson Strong-Tie ZMAX 185 joist hanger. Depending on the size of your deck, this could become a large-scale project requiring a fair amount of time and effort, so you may consider having a contractor do the work for you.

For more information about ACQ pressure treated lumber please visit Greentree Wood Products’ website at www.greentreewood.com.