Deck-Cleaning DIY Advice...
The First Step For Refinishing Decks

Deck-Cleaning 101... Did you know, one out of every four homes in America has a wood deck? That's a lot of deck-cleaning to be done! Did you know that more deck-building on to existing homes is happening at a rate of over one million per year? Wow! Imagine how many of those need cleaning...

The goal is to prolong the life of your deck. Since you're reading this you already recognize the benefits to maintaining your deck...or maybe it just looks like crap and you're ready to do something about it! When your deck was new, you probably coated it with a clear or pigmented finish to beautify and protect the wood's surface. Now...

The effects to your deck exposed to the elements, dirt and mildew day-in and day-out, the wear and tear of foot traffic or the effects of insect infestation have taken it's toll. These effects happen rapidly to un-coated decks, even if your deck is finished, eventually it will fall victim to the ravages of weathering in a few years and need to be cleaning and refinished.

To achieve the prolonged life we're looking for you must conduct some periodic maintenance, the first and subject of this page, is deck-cleaning. The essential first step prior to refinishing a deck. I'll introduce to you some of the products and methods to clean and restore your wood deck. These include chemical as well as mechanical means. Before we get into the methods, let's talk about what causes the discoloration of decks in the first place.

What Causes Discoloration in Wood Decks?

Foreign material such as dirt, bird poop, tree sap, or the drippings from you BBQ grill...

Fungal discoloration from mold, algae, moss lichen and sap-stain growth...what? (Trust me on this one...I consulted experts with much bigger brains than me.)

Nail and other iron stains, tannins and other extractive from the wood. Graying is caused by surface decomposition by sunlight and moisture, and fading due to weathering of coatings.

Whatever the cause, and I'm sure this is WAY too much information, it requires some effort to be removed prior to refinishing. If your deck-cleaning efforts are insufficient, you run the risk of the dirt or mildew (or bird poop) interfering with the performance of your newly applied coating.

Deck-Cleaners and Restorers

Chlorine-Based Bleaches...

Are your typical deck cleaning products found on the shelf at your local home supply store. The bleaches used in these deck-cleaning products are typically used in laundry detergents and some are swimming pool additives. The bleach additives are effective against mildew but do little to remove dirt or other surface deposits. In fact, they can do more harm then good by bleaching out the natural color,if not rinsed properly the chlorine salt residue can cause premature graying of wood fibers.

NOTE:Household bleach and other products containing chlorine-based bleaches should not be mixed with products containing ammonia.

Oxygen-Type Bleaches...

Products in this category are based on a chemical commonly known as Sodium per-carbonate, a powder that when added to water forms hydrogen peroxide)....a common oxygen bleach, and Sodium Carbonate (Soda Ash). Hydrogen peroxide is effective in removing mildew stains and the weathered gray residue from UV (sunlight) degradation. It acts like a built-in detergent, removing dirt and other deposits. Thus these Oxygen-type deck-cleaners are a good choice because they not only remove mildew, they also remove the dirt and weathered gray residues...returning the deck it's natural original color.

Oxalic Acid-Based Products...

NOTE:Concentrated oxalic acid is toxic and should be handled and used with care...consider consulting a professional before going it alone.

Preparing for Refinishing For a New Finish...

Strippers (no not that kind!)

Chances are you are going to have to removed what's left of an an old finish. Most deck-cleaners can't remove the old stains or paints. Typically you can accomplish this by mechanical means or chemical.

Many of your chemical paint strippers come ready-to-use off the shelf. They are based on organic solvents, caustic salts such as sodium hydroxide or sodium meta-silicate (did I say the right?). Depending on formula they can be effect at removing oil based or latex stains and paints.

NOTE: Most strippers are potent and require proper care and handling. Contact with the skin or eyes must be avoided and proper protective clothing and equipment most be worn as prescribed in the product labels. Careful rinsing to remove all residual amounts of the stripper before reapplying the new finish is important since it can interfere with the new coatings.

Mechanical Deck-Cleaning

Mechanical methods for deck-cleaning or restoring include planing, sanding or power washing. Planing actually removes the outer surface of the wood exposing fresh new wood. It would require intensive labor because the wood must be removed, all fasteners or nails removed, and passed through a planer. I suppose if you have a deck made with a precious wood such as redwood or IPE I might consider this over just replacing the boards.

Sanding is an effective way of removing old finish but I've read that on woods containing tannins it often results in an excessive amount of resin bleeding. Since I'm on the east coast and don't see any redwood...I'll take their word for it.

Power washing is the deck-cleaning method favored most by contractors. Used in conjunction with chemical cleaners it is very effective at removing dirt, mildew, algae and that gray weathered residue from most wood surfaces. It's also very effective at removing old coatings. Just apply the cleaners as prescribed by the manufacturer and follow up with a wash/rinse from a power washer. Power washers can be rented from your local home supply, paint supplier, or tool rental store. There are also affordable models available for purchase from tool stores and home supply centers.