In the last few weeks I have done a couple of deck restorations for some of my Denver-area carpentry clients. The first deck was a relatively new hardwood deck, which I have cared for in the past. It had been three years since I was last there performing routine maintenance. In our climate, this is a bit on the longish side for the oil based products I prefer to use. I oil my own hardwood deck about every 18 months or so — spring one year, fall the next. I can oil my entire 650 sq feet or so deck in about 6 to 8 hours. One afternoon’s works is not that big of a time commitment. My client's deck, however, had not seen the same level of preventive care that I perform on mine; mainly this has to deal with snow removal. Her site and roof pitch result in snow piles lingering on the deck for many consecutive months. This higher moisture load results in more soiling and mildew.
Oxygen based cleaner
The primary ingredient in Penofin’s cleaner (my preferred brand) is Sodium Percarbonate. When mixed with water it yields Hydrogen Peroxide and Soda Ash (the other main ingredient, in Penofin’s cleaner). This hydrogen peroxide further breaks down into water and oxygen, and as far as “green” cleaners go, it is one of the best. As you might expect, the cleaning power of hydrogen peroxide is pretty nice. It also does a good job of lightening the wood. It does not lighten the wood to the level of “peroxide blonde” but it does get rid of that weathered gray look. The sanitizing nature of peroxide is a great mildew cleaner as well. Unlike bleach solutions, this oxygen-based cleaner is better for the wood as its pH is much more wood friendly. If you have a wood deck…skip the bleach, and use oxygen cleaner.
The Sodium Percarbonate based cleaner is a dry powder that is mixed with water before use. I like to mix up a gallon or so at a time in a 5-gallon utility pail. I then transfer this to a garden pump sprayer to apply it to the deck surface. I found that this helps keep some of the un-dissolved bits from clogging the sprayer if the mixing phase is rushed or mixed directly in the sprayer. Before the cleaner is applied the wood is hosed down with water. This product works better when the surface is kept in a wet state. A few minutes after being applied, the surface will foam up like when hydrogen peroxide is applied to a cut or wound. To ensure a more thorough cleaning I scrub the deck surface with a deck scrubbing broom. A rinse with the garden hose removes the loosened dirt and grime, and then the deck is looking refreshed.
Power washing tips
In some cases I will use my power washer to rinse away the dirt and grime as some of my clients are on wells and their water pressure is a bit low. If power washing, this step needs to be done with great care as a power washer can quickly damage wood if used too closely. With a hardwood deck, this is less of a concern, and can sometime speed the overall process. With softwood decks the scrubby brush and garden hose work just fine, though a bit of elbow grease is involved.
The next step is to “brighten”
The next product in Penofin’s cleaning regime is the “brightener”. This product is oxalic acid-based and removes some of the tannin staining that is so common in some wood species. Like the cleaner, this product is a dry powder that is mixed with water and applied in the same manner. Here it is important the keep the surface wet as well. The acid nature of this second product brings the pH of the wood back into balance, which will prolong the wood’s life. Once the cleaning steps are complete I allow the deck to fully dry a few days before applying the final oil based product.
The second deck I restored recently was a softwood deck that had seen many, many years of no care at all. After cleaning and oiling (this deck was treated with Penofin’s Verde line of Zero VOC oil, which is made from 100% sustainable components) the deck now looks presentable and ready for the next BBQ. As an added treat, the rough weathered railings on this deck were sanded down to a splinter free state. The patina of near 20 years of Colorado sun still shines through, with some more regular care, this beauty can be preserved for years to come.