Treated wood put in place before 2003 was treated with chromated copper arsenate, and wood pressure treated after 2003 is treated with amine copper quat and copper azone or other chemical combinations. The smell they leave in the wood is not pleasant. Sealing pressure-treated wood adds a protective barrier over the toxic chemical preservatives that make the wood smell bad. It also protects the wood from cracks, twisting, warping, cupping and discoloration by blocking the sunlight and slowing the evaporation of water and chemicals from the wood.
Things You'll Need
Oxygen bleach cleanser
Sealer formulated for pressure-treated wood
Clean the wood thoroughly with a scrub brush that has been dipped in an oxygen bleach cleaner. Oxygen bleach will penetrate the wood's surface without damaging the wood surface color. Do not use chlorine bleach; it will bleach the wood to an unnatural color.
Spray the wood with a garden hose and allow it to dry for 48 to 72 hours.
Seal the wood by applying a treated wood penetrating water-repellent formulated with synthetic oils and resins. Large hardware stores will have the specific sealers that have mildeweides (mildew preventives), algaecides (algae preventatives) and ultraviolet blockers. By locating a sealer that has these three items, you seal the smell of the chemicals in the wood and protect the wood from the elements that cause the smell to be released into the air. Follow the application directions on the sealant that you purchase. Multiple coats may be necessary.
Wear protective equipment like gloves and a respirator if you have to cut or sand treated wood.
Newly installed pressure-treated wood needs to cure before stain can be applied, but it can be sealed immediately after installation.