Oregon Construction Contractors (CCB) Practice Test

Should aluminum and galvanized flashing come into direct contact with pressure-treated wood?

1. Yes, it should

2. No, it should not

3. Only if sealed properly

4. Only if tested

The correct answer is: No, it should not

Pressure-treated wood is often infused with chemicals to prevent decay and insect damage. However, these chemicals can be corrosive, especially to materials like aluminum and galvanized steel. When aluminum or galvanized flashing is placed in direct contact with pressure-treated wood, it can lead to accelerated corrosion of the flashing due to the chemical reactions between the copper-based preservatives used in the treatment process and the metals in the flashing. To prevent this potential issue, a barrier, such as a plastic or rubber material, should ideally be used between the flashing and the pressure-treated wood. This mitigates the risk of corrosion while allowing both materials to function as intended in a construction setting. Understanding this interaction is crucial to ensure the longevity and effectiveness of flashing in construction applications involving pressure-treated wood.