Plastic decking – How do I maintain it?

Plastic Decking  is a Major Investment

The plastic decking on a dock is a major portion of the dock investment.  It does take time and effort to maintain it properly.  This is particularly important on marine structures vulnerable to the elements.  Most plastic decking requires yearly maintenance to appear attractive for years to come.

Why does my decking appear to be dirty and what causes it?

Mold/mildew is the common term used to describe a growth on the surface of matter.  It’s caused by fungi, especially in the presence of dampness.  Under a microscope, mold has an octopus-like structure.  Its legs attach to a surface in a web-like manner.  Once a mold has successfully colonized, it releases thousands of new spores. This growth makes your deck appear dirty over and over again, making your deck appear dirty.

What makes the mold grow?

Molds need three things to grow:

  1. Food,
  2. Moisture and
  3. Temperate weather.

When the spores are in a favorable environment, they will germinate.  The spores settle out of the air or are deposited by rainwater and wet feet.  As a result, they will be more prevalent on horizontal surfaces (like your decking panels).  The colonies do not migrate, but rather establish colonies and release even more spores.

Plastic decking is inorganic but nature deposits “food” and moisture in the form of rainwater. Birds deposit further nutrients and you carry moisture, suntan lotions and dirt from the environment and deposit it on the decking.

While plastic surfaces appear sleek and impermeable, plastic docks still cannot escape the mold/mildew cycle.  Docks still need to be cleaned with regularity.  This is particularly true with HDPE plastic decking (usually recycled, solid plastic boards.)

Without damaging the environment, how can I clean the mold and common dirt off of my plastic decking?  

We all know that we must avoid introducing pollutants, including soaps and most other commercially available cleaning products into our waterways. Still, you do have some options.

Cleaning methods for Plastics

Note – In all cases mentioned here the use of safety gloves, face masks and eye protection is highly recommended.

Use a natural biodegradable cleaning solution that removes buildup without damaging the decking material or the environment.

Among your choices are:

  • Use a Pressure washer;  or
  • Hand scrub the decking with a commercially available bio-degradable cleaner like “OxiClean”
  • NEVER use chlorine bleach

Pressure washers require patience and care

The use of a pressure washer must be done carefully even though there is no “grain” involved in the decking.  Too much pressure when spraying can cause physical damage to the decking material.

Never allow the pressure head to get closer than 12 inches to the surface.  Use a “fan” nozzle with a 20 degree tip to reduce the pressure.  Never use more than 1800# of pressure.  The less pressure at the sprayer head, generally the closer you can get to the surface.

Hand scrubbing

Using a hand brush with natural or plastic bristles and a commercially available product like “OxiClean” is a safer way to wash the decking.  “OxiClean” breaks down to oxygen, water and soda ash so it won’t harm the environment.  OxiClean uses oxygen ions to neutralize stains and dirt.

Many scrub brushes allow you to use a pole handle so you do not have to kneel down and it will be more comfortable for you.  Do not press so hard that the bristle bend to the side as the real cleaning takes place at the ends of the bristles.  If there is a wood like pattern in the decking surface try to follow that direction.  This allows you to get deeper into the grooves with less effort.

Get into the deck spacing as far as possible to make the decking look even better.  Before the decking dries, rinse the decking with clear water.

If the product you choose has oxalic acid (very corrosive) or chlorine bleach we strongly recommend that you do not use it because it is not bio-degradable.  It could also get you a major fine from the DNR.

As an extra caution check the label of any product you plan to use to see if it contains harmful ingredients like hypochlorite bleach.  ALWAYS use the smallest concentration to do the job while observing safety protocols.

Found this article helpful?  Call Jerry at 920-493-4404 or Email for more information.  Also go to “NEWS” on any page of our website for a complete list of articles meant to keep you informed on the latest product information and maintenance issues.