Chemicals That Will Make Pressure-Treated Wood Rot

Nicole Schmoll

Pressure-treated wood undergoes a rigorous preservative process to protect it against damage from exposure to weather, water, fungus, rot and insects such as termites. Pressure-treated wood serves a variety of outdoor purposes, including railroad ties, playground equipment, boat docks and decks.

Painting or sealing a pressure-treated deck too soon can cause it to rot.

The wood is treated with chemicals that are forced by pressure deep into the wood. The treatment is so effective that pressure-treated wood is often guaranteed against damage for 40 years. There are, however, a few things that consumers can do to cause pressure treated wood to rot.

Water-Based Stain

After purchasing pressure treated wood for a project, such as an outdoor deck, it is common for consumers to want to seal the wood with a water- or oil-based sealant. This is fine if the wood is allowed to thoroughly dry. Coating pressure treated wood with a water-based stain too soon after purchase can cause the moisture and chemicals inside of the wood to become trapped beneath the sealant. The main ingredient in water-based stains is water. This along with the coalescing agents in the stain can interact with these chemicals and ruin the wood.

Oil-Based Stain

As with water-based stains, applying an oil-based stain to pressure-treated wood without giving it a few months to weather can ruin the integrity of the wood. Oil-based stains commonly contain solvents, binders and metallic salts that allow the stain to penetrate the wood and dry properly. These ingredients can interact with pressure treated wood in a harmful way when applied too soon. Experts recommend using a semi-transparent oil-based stain about two months after exposing pressure treated wood to the outdoors.


Applying paint, particularly before pressure-treated wood has thoroughly dried, is one of the very few things that can cause pressure treated wood to rot. Because pressure treated wood has moisture penetrated deep into its fibers, it can take a few months for all of this moisture to release itself into the air. Latex and oil-based paint seal the moisture into the wood, preventing it from escaping and causing the wood to rot. If you want to paint wood for an outdoor project, buy untreated wood, seal it with an oil-based sealer to protect it and after that has dried completely, apply the color of paint you desire.