Finishing deck is an optional step if you want to apply a stain to alter the appearance of the wood used to build a deck. Sealing a deck is necessary if you have used a wooden material, as this will protect it from water and other elements, to extend its life span and improve its overall appearance. There are a couple options for your finish, including transparent stains and water repellants and semi-transparent stains.
The way you should handle finishing and sealing a deck will depend on whether you are using a native wood, a tropical wood, or a pressure-treated wood, as they will respond differently to various finishes. Deck finishes generally include a sealant and stain for a hint of color, but sealants can be purchased without applying a stain.
Start with a clean, dry deck, and use a roller to apply a coat of the finish of your choice to your deck as directed, always keeping a wet edge, and working quickly. Allow the deck to dry and cure for at least 24 hours before applying a second coat, walking on it, or bringing furniture out on to it. Though finish can be applied with a sprayer, rollers are recommended for a more complete and protective finish.
Transparent Stains and Water Repellants
Transparent stains and water repellant finishes do not contain pigment that will alter the color of the wood but provide the necessary water repellant protection to prevent water damage to the wood. These generally also contain fungicides and mildewcides to help prevent their growth. Many options also contain ingredients to either block or absorb UV rays to protect against fading from the sunlight.
Semi-transparent stains are finishes with small amounts of pigment to change the appearance of the wood while providing an additional element of strength and durability. Higher quality stains will include water repellants and mildewcides to protect against water and fungus damage, and the pigments will contain the UV blockers to protect against sun damage. Latex based semi-transparent stains may form a film and cause cracking and peeling, but others should not form a film.
Finishing and Sealing Native Woods
Native woods such as cedar should be finished and sealed using a penetrating finish such as the ones mentioned above, because these finishes will not form a film on the wood. Finishes that are non-penetrating cause a film to form on the deck surface will cause them to crack, flake, and peel, which makes the deck harder to maintain and re-finish.
Finishing and Sealing Tropical Woods
If your deck is made of a tropical wood such as ipe, leaving it unfinished will result in a silver or gray color that many people like; however, sealing it will help protect it from the elements, as well as damaging UV rays. It is sealed much like any other wood deck, but it is important to remember that it will not be as accepting of the finish. Since less of the finish will penetrate tropical woods, in order to maintain the finish and appearance, you will have to apply it more frequently.
Finishing and Sealing Pressure-Treated Woods
If your deck is made of a pressure-treated wood such as southern yellow pine, you should choose a finish based on how much sunlight the deck will get. A deck in direct sunlight will do better with a lighter colored stain because using a dark stain will cause the wood to get hotter. If the deck does not get a lot of sunlight, you should stick to a water based stain rather than an oil based stain.
Pay close attention to the directions on the finish label, and look for a finish that can provide UV protection if you do not want to risk your deck fading or turning gray. Some woods, such as cedar or redwood can be sealed and finished right away, while others, such as pressure-treated should be allowed to acclimate for about a month before being finished and sealed.