Pressure Treated Wood and Aluminum

You may like the look of pressure-treated wood but you should think ahead before you use it.

The new pressure-treated wood uses Alkaline Copper Quaternary (ACQ) or Copper Azole (CA), which has replaced the Chromated Copper Arsenate (CCA) wood preservative. ACQ and CA are available in a brown or green shade for the exterior residential markets, and they also both meet Health Canada Standards.

When using the new Pressure-treated wood – ACQ and CA, keep in mind that they do have a higher concentration of copper, which results in a chemical reaction that discolours and corrodes aluminum and some metal fasteners.

For fascia board applications, spruce, pine, and fir lumber are recommended to use instead of pressure-treated wood, as most fascia boards are capped with aluminum to protect the home from water or other damage.

If pressure treated is preferred (although not recommended), an ice and water shield (Lastobond Pro-HT) or Resisto Red Zone must be used to cover the whole area so that the pressure-treated wood and aluminum never touch.