As the surface of a wood deck is exposed to sunlight, dirt, mildew, rain, or snow, it will eventually deteriorate in appearance. This phenomenon occurs fairly rapidly to uncoated wood. It can be prolonged from occurring by the use of a protective finish; however, even the best finish will succumb to the ravages of weathering in a few years and will need to be refinished. Proper cleaning and restoration is an essential first step in the refinishing of wood decks. There are a variety of products and methods to clean and restore wood surfaces. These include chemical as well as mechanical means.

CAUSES OF DISCOLORATION:
There are a number of sources of discoloration of wood decks. These include:
Dirt and other foreign materials such as tree sap, bird droppings, grease, etc.
Fungal discolorations from mildew, mold, decay, and sap stain growth
Algae, moss, and lichen growth
Nail and other iron stains
Tannins and other extractive's from the wood
Graying of the wood due to surface decomposition by sunlight and moisture
Fading/decomposition of weathered coatings.

Some of these discolorations are chemical in nature; others are biological. All should be removed prior to refinishing. In addition to being unsightly, these discolorations and the agents that cause them can significantly interfere with the performance of subsequently applied coatings. Thus their removal is important from a performance as well as an aesthetic standpoint. Now on to the procedure for proper deck restoration which includes two steps, first cleaning and then stain removal and brightening.

DECK CLEANERS:
Household cleaners and bleaches can be effective to some extent but they have their limitations. Also, since they are not usually designed for deck cleaning applications they can present some handling problems. For cleaning wood decks and the exterior of your home I recommend either one of these two products...

Trisodium phosphate has been used by painters for years and years as a heavy duty degreaser and all purpose cleaner. TSP is formulated for removing Grease, soot,and lead paint dust cleanup. A washing of surfaces prior to painting helps insure a good clean "bite" for the finish coats of paint. TSP can be mixed with a small amount of laundry detergent to help keep it wet longer and penetrate deeper into the surface dirt. TSP does little for mildew which we will discuss later on.

Hy-Tech House Wash is a complete environmentally friendly powdered concentrate that is simply mixed with water. This product is formulated with oxygen bleach and other agents for deep penetration, long "wet time", ease of use and will not harm wood fibers, pets, grass, or most plants.

DECK BRIGHTENERS AND RESTORERS: After cleaning to remove dirt, grease and other foreign materials the next step is to remove the natural "graying" and lighten other stains. There are countless "old home recipes" for solutions to brighten wood.

CHLORINE BLEACH: Chlorine kills algae, moss, and mildew. BUT - chlorine breaks down the lignin holding the the wood together, causing excessive damage to otherwise healthy wood. Chlorine is dangerous, environmentally unsound, and likely to cause problems with surrounding greenery. If you must use it we recommend using no more than 1 cup per gallon of water.

ACIDS: There are numerous acidic compounds in common use as wood brighteners, such as citric, oxalic, and even phosphoric. Phosphoric is fast, dangerous, and ecologically unsound. It is banned in some states and faces ever-tightening restriction or even elimination as time passes.
Citric acid is a little slower, easier to control, effective, non-hazardous, and quickly gaining popularity.

Oxalic acid, "wood bleach", is used to remove stains and lighten darkened gray weathered wood. A solution (four ounces per gallon of water ) of oxalic acid crystals dissolved in water should be applied to the discolored area. Stains will fade and disappear in twenty minutes or less following this application.
New Pressure treated lumber: A treatment of Oxalic acid will open up the mill glaze and allow you to seal or stain the wood. I have never been an advocate of the old rumor that "you should let it dry out for a year". Leaving any wood unprotected for a year only leads to a dirty gray look, splitting and cracking. Oxalic acid is also used in commercial rust removers to remove iron rust stains from tubs and sinks.

OXYGEN BLEACH: (Disodium Peroxydicarbonate, not to be confused with sodium bicarbonate)... is Biodegradable, Non-toxic, Color-safe and Fabric-safe. It is not harsh like chlorine bleach. It's mildly acidic and may be used to help neutralize previously-applied basic cleaners. Environmentally friendly, sodium percarbonate will react with water to form hydrogen peroxide, which acts as both cleaner and slightly acidic bleach/brightener. A great benefit is that the hydrogen peroxide will evaporate and leave behind no pockets of acidic solids. The hydrogen peroxide is unusually effective in lightening heavily darkened wood. Except for industrial-strength cleaning or stripping jobs, sodium percarbonate is our hands-down choice for most average wood preparation jobs.

NOTE: Guys once your wife finds out that this will remove practically ANY stain from ANY surface or fabric, you will have to hide your deck cleaning supply. Find mixing recommendations and more about the many uses of
Oxygen Bleach Mixing Instructions

Fungus growth and insects can be controlled after cleaning by treating with Natures Own Fungicide~Insecticide.

Power Washing- For washing large wood decks and house cleaning prior to painting, power washers make the job fast and easy.
CAUTION: The extreme pressure will break up the wood fibers leaving a fuzzy wood finish of broken wood fiber.  Not only does this shorten the life of the wood,it also leaves you with poor surface to refinish.  Locking down the loose fibers requires more effort and material. There is no need to use one of the giant 3000 psi machines designed to remove multiple layers of paint from cement and stucco, a 1500 psi or smaller machine with a wide fan tip will do a nice job without destroying everything in its path.

Wood Decks Intro ~ Cleaning( You are Here ) ~ Materials for Staining ~ Application