A pressure treated wood deck needs special consideration when staining or sealing it. This type of lumber has preservatives (including arsenic) that are forced deeply into the wood fibers to protect against rot, mildew, and termites. Because of these characteristics, it is one of the most preferred materials of deck builders and homeowners alike, so the odds are very high that this material has been used for en existing deck outside your home or will be used to build a new deck. Below you will find information about what you need to do to stain pressure treated wood correctly.
Step 1 - Cure the Wood
Pressure treated wood takes about two months to "cure" after it is installed before it can be stained, so make sure you've let at least this much time pass before you attempt to start on this project.
Step 2 - Clean
Clean the deck of any debris or dirt. Start by sweeping up loose dirt, twigs, and leaves with a broom and dustpan. You can follow up with a pressure washer to clean the wood, especially if there is a lot of grime buildup, but be careful with it. A pressure washer can damage the wood if the pressure setting is too high or if the nozzle is held too close to the surface. Hold the tip about 12 to 16 inches above the surface and start with a psi of about 1,500, monitoring carefully to ensure the wood isn't getting gouged. Allow the deck to dry at least two days before proceeding.
Step 3 - Prep Surrounding Structures
Oil-based stain is very thin and easily splashed or sprayed on nearby areas inadvertently. Cover the underlying concrete pad, surrounding bushes, or grass with tarps to protect them from getting coated.
Step 4 - Apply Stain
Overall, applying stain with a paintbrush will give the best results. The bristles work the stain into the wood grain for a more even, vivid color. You can, however, use a roller to spread it(in which case you will still need to use a brush for small, tight spaces) or a sprayer. While both of these are much more efficient than a brush, neither will achieve the same finished quality. Make sure to read the product label on the particular stain you are using for any specific application instructions it might have.
Step 5 - Test the Seal
A second coat can be applied after the first has fully dried. The best way to tell if the deck needs another is to spray some water on it. If the water is absorbed by the wood, it is not sealed, and second layer must be added. If the water beads, there is a good seal and you don't need to add more. However, you much make sure that more stain is applied the following year to maintain the integrity of the seal.
Note: Make sure your stain has a sealer in the formula or else you will need to buy a separate product to coat the deck in after the stain is finished drying.