Deck Cleaning and Wood Deck Stains - A Do It Yourself Guide

Looking out your back window you decide that it's once again time to get your deck ready for the coming season. The grill still has its winter cover and the patio furniture is stacked into the corner. You can envision how the deck is going to look when its finished but that small hollow in your stomach reminds you how cumbersome deck cleaning and staining can be. If you use the right types of products, the task can be performed much more simply. The key to making a finish last is all in the preparation work you do before you apply that first drop of stain.

Deck Stain or Sealer: How Do I Choose?

Exterior wood is subject to damage from the elements. The constant cycle of moisture and sun drying will cause deck boards to warp, check, cup and splinter. It is essential not only to try and seal out moisture but also to use an oil based staining product to keep the wood conditioned. Think of a drop of water placed onto your skin. Once that water evaporates, the moisturizing effect is cancelled. This simplified analogy is akin to putting water based (or water borne) staining and sealing products on your deck. Using the same analogy, now think about placing a drop of baby oil onto your skin. The oil acts as an emollient keeping your skin more pliable. This is why we recommend using oil-based products for wooden decks. Oil acts as a better moisture repellant and will retard the drying effect, which causes premature aging. Oil based sealers will add years of life to your deck.

You may have noticed the switch back and forth between the words "stain" and "sealer". Professionals use these words interchangeably. Think of exterior grade wood products as a hybrid of these two words. Deck staining products are actually tinted sealers. You cannot use a stain followed by a urethane or varnish sealer like you would on an interior project. Moisture would attack this combination and your floorboards would become a peeling mess. Sealers block out moisture and the pigmentation in them provides UV protection so the wood will not turn gray. The most maintenance friendly stains will be semi-transparent and deep penetrating oils. Film forming, also know as solid staining, products will provide good initial protection but they can be prone to peeling and are very difficult to remove. If you don't already have a solid stain on your deck, you may want to avoid applying one, as there is no turning back from that decision.

Starting Fresh: Choosing The Right Deck Cleaning Products

Many of the deck cleaners that are sold at Home Centers such as The Home Depot and Lowes contain sodium hypochlorite, known more commonly as household bleach. While bleach is an effective mold killer, it does not address the issues of dirt trapped inside the wood or allow easier removal of grayed wood fibers. Both dirt and grayed wood will contribute to premature finish failure. In addition, sodium hypochlorite affects the lignin in wood to a great degree. Lignin is the "glue" that holds wood fibers together. If you were to look at a cross section of a piece of wood that has been cleaned with bleach under a microscope you would see a jumbling of the fibers. This cross weaving of the fibers can cause problems with stain/sealer penetration. This again means less life from your deck stain as well as a potentially blotchy finish. Bleach also causes wood to become unnaturally whitened or washed out.

The majority of deck restoration professionals use a two step deck cleaning process involving a landscape-friendly cleaning agent called sodium percarbonate followed by an acidic based cleaner for pH balancing. Sodium percarbonate is considered an effective mold killer. When the powdered chemical is mixed with water, hydrogen peroxide and soda ash are released. This oxygenating reaction bubbles dirt and contaminants to the surface for a deep cleaning effect. This reaction also loosens sun damaged gray fibers allowing them to be gently scrubbed with a medium bristled brush and rinsed with a garden hose. You could also use a pressure washer set to pressure below 800 p.s.i to facilitate faster rinsing. Certain types of sodium percarbonate based wood cleaners also contain other ingredients which help to emulsify old, failing finish.

After you finish the first step of the cleaning process, while the wood is still wet, you apply an acidic cleaning agent. This will serve to pH balance the deck after cleaning. An added effect is that the wood is brightened and the tone of the deck will be evened out. Acids used for this step are usually oxalic, citric or a combination of both. Oxalic acid can be irritating to the lungs. After your final rinsing, the deck is now perfectly primed to accept the stain/sealer of your choosing.

Seal Out The Elements Using A High Quality Oil Based Sealer

Try to choose your staining products wisely. Paint stores such as Sherwin Williams or Benjamin Moore will carry higher-grade wood deck stains. As with anything in life, you get what you pay for. Spend a little more up front and you may not have to stain your deck as often. Avoid products that contain acrylics. These products will build up over time and create a finish that is next to impossible for the DIY enthusiast to remove without using very strong caustic chemicals.

Applying the sealing product can be done via spraying, brushing or mopping. If you spray, be sure to back brush the product with a china bristled brush to work it into the wood and prevent runs. Most oils stains need to be applied in what is called a wet-on-wet coat. The first coat is applied and allowed to penetrate the wood. Within a short time span before the product dries you apply another coat. Be sure to always follow manufacturer's recommendations and the directions on the can.

Maintaining the Deck

Allow the wood to dry for 72 hours before placing furniture back onto the deck. While the deck stain/sealer is still intact it is okay to use a light mix of bleach and simple dish soap to periodically clean away any mold or dirt from the surface. If you follow a simple maintenance plan of recoating the horizontals (floor and handrails) every year with a light coat of oil and doing the rail system every two years, your deck will always look fresh and it will last you a lifetime.

Ken Fenner is the owner of PressurePros, Inc a pressure washing company located in Havertown, PA. PressurePros is also the parent company of Restore-Deck a distibutor of deck restoration cleaners and deck stains. Ken also the administrates a do-it-yourself BBS called the DIY Chat Forum.

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