Care & Maintenance Guidelines for Composite Deck & Railing

CLMA Technical Bulletin

Care & Maintenance Guidelines for Composite Deck & Railing


Wood plastic composite decking and railing products are designed to provide low-maintenance usage, enjoyment, and dependability for extended periods of time. In an outdoor environment however, exterior building materials require periodic maintenance and cleaning, including composite materials.

The Composite Lumber Manufacturers Association (CLMA) has established the following guidelines regarding cleaning, care, and maintenance of wood plastic composite decking and railing systems. Always consult the product manufacturer for specific recommendations.

Debris, Dirt, & Grime

Periodic cleaning can help reduce the buildup of dirt, grime, and other organic debris on the surface of the deck or railing. For larger debris like leaves and grass, a soft bristle broom or blower will usually work effectively to clear the deck surface. For a more thorough cleaning, a deck wash containing sodium hypochlorite and a garden hose or pressure washer can be used to wash the deck clean.

Caution! Always consult the manufacturer to determine whether a pressure washer can be safely used to clean the deck or railing surface. High pressure washing can damage decks and railings if appropriate precautions are not utilized. If a pressure washer is an option for your specific product, caution must be taken to not exceed the maximum pressure (psi) as recommended by the manufacturer. The distance of the nozzle tip to the surface of the decking or railing can affect the pressure at the surface of the product being cleaned.

Ice and Snow

For removal of snow and ice, calcium chloride or rock salt can safely be used on the surface of the deck. Care should be taken to not walk on the decking during this process as the ice melt granules can gouge or scratch the deck surface. These products may leave behind a white residue from their application, which can be removed by rinsing the deck or cleaning it with a mild soap and water solution. If shoveling snow off of the deck, always use caution. It is not recommended to use a metal or plastic shovel with a metal leading edge or other sharp-edged tools to remove ice or snow, as these tools can cause damage to the deck surface.

Mold and Mildew

Mold and mildew growth occurs to varying degrees in all regions of the country, especially those subjected to warm, humid conditions. Leaves, pollen, grass, and other organic debris provide a food source for mold; with periodic rinsing of the deck or railing surface accumulation of these materials can be minimized.

If mold or mildew is present on the deck or railing, commercial cleaners are available to remove and inhibit future growth. Manufacturers of composite decking and railing typically provide recommendations regarding the appropriate cleaners to be applied to their products. It is important to consult the manufacturer’s recommendations before applying any commercial cleaning products to mold or mildew on the deck. Note: Any cleaner used has the potential to lighten the color of the decking or railing; always test on a small portion of the decking or railing before cleaning the entire surface.

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Rust Stains

Rust stains can appear on the surface of a deck or rail as a result of metal items placed on the deck or rail. Commercial cleaning products containing oxalic or phosphoric acid (generally known as deck brighteners), can be used to lighten or remove these types of stains. The use of plastic or vinyl tips on metal furniture feet may aid in preventing stains.

Oil and Grease Stains

Precautions to prevent grease and oil spills on composite deck and railing products should always be taken, and it is important to clean spills immediately if they occur. Household degreasing agents will usually remove stains if applied immediately. If the stain has set into the surface, other commercial cleaners are available that may reduce or remove its appearance. If a slight stain remains after cleaning, a short period of normal weathering will often lessen, if not completely diminish, the stain. Be sure to follow the manufacturer’s recommendations on the appropriate commercial degreasing agent to apply to the deck or railing surface.

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