How to Clean Your Wood Deck
The first wood deck ever constructed was built on May 3, 1857. On May 4, 1857, the proud owner of this new deck asked, “How do I take care of it?” Of course, those dates are totally fabricated, but homeowners have been trying to find the best way to maintain their decks since. Cleaning your deck is the first step in deck maintenance.
Taking care of your deck entails a number of steps, depending on the end results you desire. Regardless of what end result you want, the first step is always cleaning your deck! In order to clean your deck, get the best results, and not damage the deck in the process, there are a few considerations you need to understand prior to getting started.
The goal in cleaning your deck is to eliminate environmental contaminants, mold, mildew, algae, and anything that has spilled on the wood. The challenge in cleaning these substances from the deck is determining the best product to use while insuring the wood will not be damaged.
Most DIY-ers (do-it-yourself-ers) rely on the local home improvement center for recommendations, and many use their own home brew of various household cleaners. Before going further, let’s take a look at some of these alternatives.
Bleach. Bleach has been a favorite cleaning solution for cleaning wooden decks for many years due to its availability and ease of use. The advantage of using bleach is that it is very simple to work with, and appears to give immediate results. The greatest disadvantages of working with bleach result from its chemical nature.
Bleach literally bleaches the wood, resulting in a lightening of wood’s natural coloration. This bleaching effect may provide initially pleasing results, but over a period of several months the wood begins to take on a lighter appearance. The natural pH of wood is just slightly acidic, and bleach is a basic solution. As a result, use of bleach on wood shifts the pH from wood’s natural, near neutral, pH to a basic pH which will damage the cellular structure.
As a cleaner, bleach provides minimal results. The natural bleaching action creates the impression of a cleaner surface which, in reality, is only bleached but still needs cleaning. Cleaning with bleach does kill mold and mildew which may be on the deck, but does not eliminate the spores from which mold and mildew grow.
Generally, bleach does not provide the desired cleaning results. Cleaning your deck with bleach is comparable to washing your hands without soap…your hands are rinsed a little, but they still need cleaning.
After cleaning a deck with bleach, it is very important to flush the deck with a mildly acidic solution using either oxalic or citralic acid to adjust the pH back to wood’s natural range, then flush again with water.
Detergents. There are a number of household detergent products which are commonly used in deck cleaning. These include general products such as tri-sodium phosphate (TSP), a simple detergent, and OxyClean. Use of detergents on a deck result in a cleaner surface, however they may not provide the desired results when dealing with mold and mildew. Detergents are best used in conjunction with a bleach solution.
DIY Products. DIY products are increasingly available at local home improvement centers and paint stores. While these products promise professional results, you should keep in mind that these products are formulated with the assumption that most DIY-ers are not experienced professionals with experienced professionals’ equipment! In other words, they’re formulated to avoid making a mess of your deck if you don’t follow instructions!
When considering use of these products, good advice is to follow instructions carefully…and plan on repeating the process at least once to get the desired results.
How do I clean my deck?
Many homeowners have decided that maintaining a wood deck is just too much troublle, and that opinion is based on attempting to do the work themselves or taking the low bid from a contractor without checking references! Cleaning your deck can become an unpleasant adventure while a professional will make all the difference between a beautiful deck and a weekend project gone bad.
New or unsealed wood. If your deck is new, or has never been sealed, the cleaning process is fairly simple. If the deck has been previously sealed, and you’re preparing it to be sealed again, your job will be more difficult.
Cleaning new, or unsealed, wood is accomplished by tri-sodium phosphate or OxyClean. Apply the solution to a workable area of the deck (around 10’ X 10’) using a pump type garden sprayer. Allow the solution to sit on the deck for 10 – 20 minutes, then rinse using a pressure washer. Water pressure from the pressure washer should be between 900 – 1000 psi and a wide angle (white) tip should be used to avoid damaging the wood. Be sure to keep the tip approximately 4” from the wood surface, and use a sweeping motion to avoid stripes in the wood.
Continue this process until the entire deck has been cleaned. Work the deck in sections to avoid drying of the cleaning solution after it has been applied.
After the deck has been completely cleaned, apply a deck brightener. Deck brighteners are available from most paint and home improvement stores. When selecting your deck brightener, be sure to confirm that the ingredients include oxalic or citralic acid. Apply the deck brightener in the same manner as the cleaning solution. Allow the deck brightener to set on the wood for approximately 10 minutes, then rinse with water. The deck brightener will restore the wood to its natural pH.
Previously sealed wood. If the wood has been previously sealed, and your goal is to remove the old seal…your job just became more difficult! Many times these decks are referred to as “stained decks”, and cleaning deck stain is your goal. Unfortunately, the cleaning solutions described previously will not remove old sealant. In order to remove old sealants, more aggressive cleaning solutions are required…and these solutions will include caustic ingredients.
The most commonly accepted ingredient for cleaning deck stain is sodium hydroxide, also known as lye. Please note that sodium hydroxide is a caustic solution which will burn any part of your body it contacts. It is very important to read labels very carefully and take precautions to avoid contact with skin or eyes, and to avoid breathing fumes from sodium hydroxide solutions. Be sure to wear protective clothing including boots, gloves, eye protection, and breathing apparatus which is rated for use with caustic solutions.
Cleaning deck stain begins with selecting a deck cleaner/deck stripper at your local paint or home improvement store. Select a deck cleaner which includes sodium hydroxide as an active ingredient. Read and follow label directions carefully. There are several important areas to keep in mind when working with caustic cleaners. First, they will hurt you! Handle them with extreme care. It is a good idea to keep rinse water handy to the job site, and vinegar is an excellent neutralizer if skin contact occurs. Second, caustic solutions will remove paint as well as stain! Be sure to mask painted surfaces around the work area prior to application. Finally, some caustic solutions will etch glass and it’s a good idea to mask off adjoining glass surfaces. During the application process, keep a garden hose handy to rinse off any areas where incidental contact with the cleaning solutions may occur.
Rinse off adjacent plantings with water, then cover them with a drop cloth prior to application. In warmer weather it’s a good idea to remove the drop cloths occasionally and wet the plantings to avoid burning due to heat build up under the drop cloth.
Apply the cleaning solution using a pump – type sprayer. It is recommended that the pump sprayer be discarded after use to avoid later accidental contact. Apply the cleaning solution to a workable area, approximately 10’ X 10’. Allow the cleaning solution to remain on the surface for approximately 15 minutes, then rinse with a pressure washer as described in the previous section. Note the cleaning results as you rinse in order to determine if the cleaning solution needs to remain on the wood for a longer period of time. Continue to clean the deck by working in manageable areas which allow rinsing before the cleaning solution begins to dry.
Due to the caustic nature of sodium hydroxide based cleaning solutions, restoring the wood’s surface pH to neutral is extremely important. After completing the cleaning process, apply a deck brightener as described in the previous section.
Not as easy as it sounds? It’s really not! There are several additional factors to consider. Pressure washing wood is a destructive process which can damage the wood’s finish. Most common is a fuzzing effect referred to as blooming. However, damage can include splintering and gouging. After pressure washing, sanding is required to eliminate wood bloom and can be accomplished using a random orbital sander with 60 grit sand paper. Orbital floor sanders can be rented from a local tool rental store, and will make the floor a much easier project. Finally, steel wood does a very effective job of eliminating wood bloom in deeply grained wood.
Although it’s not required, sanding will leave the deck in a beautiful finish that is free of splinters…much easier on bare feet!
If your next step is sealing and staining, you’re now ready to go. Just keep in mind, cleaning your deck is an annual process and sealing or staining with conventional products will need to be repeated within 2 years.
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