Deck Cleaning

Wood decks require proper protection and cleaning to guard against the damages that will result from water, sun light, mold and mildew, and contamination. However, cleaning your wood deck requires you to know a little bit about chemistry. Knowing how to properly use your cleaning solutions and how the solutions will react with the wood will have a huge impact on the overall performance of the sealer or stain, the longevity of the wood and woods aesthetics. It is also important to know that even though the tree is dead, the wood still contains chemical compounds that work to improve the performance of topcoats and the life expectancy.

Redwood and Cedar are great examples to use as I explain the “dos and don’ts” of deck cleaning. These particular woods are filled with organic components known as extractives. Woods containing extractives require special attention with regards to cleaning solutions. Some of these organic compounds include:

• Tannins
• Flavonoids
• Quinines
• Lignans
• Carbohydrates
• Alkaloids
• Proteins
• Inorganic material

It is crucial to know if your wood deck contains extractives because cleaning solutions have undesirable effects on these compounds. Negative reactions include discoloration, compositional breakdown, and actual wood deterioration. Before using just any cleaning solution, it is in your best inertest to pay special attention to woods like Redwood and Cedar to avoid disastrous reactions.

It is very common for homeowners to purchase cleaners that contain bleaches and phosphates because they are very common over the market products. With these cleaners, you will not notice any terrible side effects at first, but over time they breakdown the structural fibers in the wood. This results in a shortened lifespan of the wood. For this reason, bleaches on wood should be avoided unless recommended by the topcoat manufacturer. With many topcoats, the bleach mixes with the acrylics to form a desired chemical bond.

The Ph level of the wood your deck is made of is an important aspect to keep in mind. For example, Redwood and Cedar are both relatively high on the Ph scale and for this reason using Oxalic Acid works great. It is perhaps the most common cleaner used on Redwood and Cedar, but it is not very good on mildew or dirt. By subjecting these woods to a high dose of acid, the wood extractives become reinvigorated and this returns the wood to its natural color and hue. Citric Acid is a more mild acid that is good to use on fine decks made from hard woods because it is not as harsh as Oxalic Acid.

If you are trying to darken your wood, you can use cleaners that contain Sodium Hydroxide. Sodium Hydroxide is very low on the Ph scale and the reaction it has with wood causes a very dark discoloration, but this is normal. If you wish to reverse the darkening then you can use an acid wash solution and the effects will reverse almost immediately. Phosphoric Acid works well to neutralize the surface after using a Sodium Hydroxide Cleaner.

Almost always, it best to use an environmentally friendly cleaning solution, except for times that the concentration needs to be altered in order to achieve desired affects. Problems such as mold and mildew buildup react poorly to acidic concentrations. It is best to use heavy basic solutions to help eradicate these types of issues. Keep in mind, in the end it still remains important to balance the wood to the correct Ph. Basically, it is better to be on the acidic side with woods such as Redwood and Cedar, but some exotic hardwoods require just the opposite.

In addition to the above cleaning solutions, new developments in the cleaning world have introduced the use of per chlorates. Per chlorates are becoming popular because they halt the oxidation reaction that commonly occurs in woods. When wood oxidizes, the wood turns gray. Per chlorates can restore the natural color of the wood. Top coats are also used as a preservation to resist or retard the oxidation process and prevent wood deterioration. They are especially useful for woods with water-soluble extractives, such as Redwood and Cedar.

Using chemicals to clean your wood deck can be very effective if you are attentive to the chemicals used in order to achieve the desired results. Careful attention needs to be given to your woods because you don’t want to rob the wood of its unique chemical compounds. These compounds help in their performance with topcoats and with its life expectancy. A properly maintained healthy deck can last you generations to come.

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