Color Restoration of Redwood products

Redwood is often preferred for siding and decks because of its attractive appearance, unsurpassed stability and the durability of its heartwood; however, left natural or with the minimal protection of poorly maintained finishes, any exterior wood's appearance will change color.

There are many causes of wood discoloration. . .

Sunlight, moisture, temperature, microorganisms, dirt and soot contribute to the discoloration of any wood used outdoors. Effects can range from wood turning a driftwood gray due to ultraviolet radiation and precipitation, to it turning nearly black as a result of mildew growth, soot accumulation or extractive staining. Black
discoloration may also result from iron in nails or other hardware or from contaminated finishes and airborne particles.

Identifying and removing mildew growth. . .

The first step toward a remedy is to identify the source of discoloration. Using simple household chemicals and a little logic, any homeowner can easily determine the cause of wood discoloration. Mildew is often a problem on decks and siding in moist environments. Mildew is a superficial fungus growth that lives on the surface of the wood but does not degrade its structure. Mildew may be found on the moist, north wall of buildings, on shaded decks and in moist areas with a restricted air flow. A relative humidity of 70 percent or more at the wood surface is ideal for mildew growth.

Mildew commonly appears as numerous small dark spots on the surface of the wood. Gray, fan-shaped areas spread below these spots as spores from the original colony multiply and are washed down the surface. Severely infested areas may appear uniformly gray or black.

To remove a mild case of mildew, scrub the surface with a mild cleanser or detergent. Next, rinse with household liquid bleach to kill surviving spores; then rinse with water. For more severe mildew infestations, use a stiff bristle brush to scrub the wood with a solution of one cup of trisodium phosphate (TSP), one cup of household liquid bleach and one gallon of water.

Commercial deck cleaning and brightening solutions. . .

Due to the increasing popularity of wood decks and natural sidings, many commercial products are available for removing discolorations and restoring the new appearance of wood. These products are available in powder or liquid concentrate form and are typically based upon non-chlorine bleaches, detergents and/or oxalic acid.
The advantage of using commercial products is that they are intended for a specific use, come with comprehensive instructions and are quite effective. Under normal circumstances, well maintained decks and siding require only periodic cleaning with such products to remain good looking.

Powerwashing is fast and effective, but it can also damage wood. . .

Powerwashing has gained wide acceptance as a method of cleaning and restoring the surface of wood siding and decking prior to refinishing. Properly performed, there are several advantages to powerwashing, including savings in time and labor costs.
Remember, though, that water and pressure are fundamental enemies of wood and that improper powerwashing can do more harm than good. For best results, hire a professional painting contractor experienced with powerwashing.
The equipment should be capable of 2000 psi operating pressure and should deliver a minimum of 4 gallons of water per minute. Under normal conditions, pressures of 1000 to 1200 psi should not be exceeded as this can result in erosion of the softer earlywood, resulting in an uneven, rough surface.
Flashing and caulking should be checked carefully before powerwashing to prevent moisture from entering the wall cavity behind the siding. Wait several sunny, dry days after washing before applying a protective finish.

Once redwood siding or decking has been cleaned and restored...

it is time to apply a protective finish. Remember, high quality products containing mildewcides, water repellents and ultraviolet protection provide the best performance. Carefully follow finish manufacturer's recommendations regarding application conditions, coverage rates and number of coats. Natural finishes are not exceptionally durable and may require reapplication in from one to three years. By maintaining these
finishes on a regular cycle, the amount of preparation prior to refinishing will be greatly minimized.

Refer to California Redwood Association's Redwood Exterior Finishes guide for further information on how to protect and maintain your exterior redwood.