It is recommended you seal pressure-treated wood used for decking or other outdoor projects. You should do this as soon as the lumber is dry. Pressure-treated wood is treated to resist rot and insects but is not resistant to moisture and sun damage. Applying a sealer will help prevent the penetration of moisture and stop cracks, swelling, and splits thereby increasing the value and longevity of your decking. If you use a pigmented stain/sealer, you can add color and slow the sun damage that would turn the surface gray. You can determine when to apply the sealer, place a few drops of water on the wood. If the water is quickly absorbed, the wood is dry and ready to be sealed. If the water beads up on the surface, the wood is still too wet to seal. It can take several months for the wood to dry out. You will need to repeat the treatment every few years to prolong the life and appearance of the wood.
Before sealing a deck you must clean it. Choose a cleaner that matches the brand of finish you plan to use. If there are any dark gray mildew stains, add laundry bleach to the solution. Pressure washing is a good option but you should be very careful not to damage the wood. Cedar is particularly soft and can be damaged by too much pressure from your sprayer. Scrubbing the decking with a stiff brush is recommended. If you notice dirt and other debris stuck between the deck boards, you can easily remove this material with an old hand saw. You literally saw the dirt out of the grooves and increase the spacing slightly as you saw.
When should you refinish a deck? Upon inspection of your deck, you will know it is time to refinish a deck when the wood looks worn, dirty and lackluster. The recommended application of sealer is with a "rough surface brush" to ensure it gets into all the cracks and pores of the wood. Attaching the brush to a broom handle will make the application a bit easier. Apply the finish so it will all soak into the wood and not pool on the surface. It should not dry as a tick surface that can peel and be damaged easily.
Weather can be harsh in Southeastern MN, so it is a good idea to maintain proper water resistance. By doing so, you will enjoy many years of use while gaining value in your home. Contact your local Rochester MN area building supply store for more valuable tips regarding maintenance of your home.