Water stains on composite decking?

Composite decking is widely used today because of its durability and minimal maintenance. And maintenance, is your time, which you save a lot by choosing a decking board.

However, just like wood planks, water stains can appear on them. Let’s find out what are the reasons for their appearance and how to deal with them.

Causes of stains

1. Tannin Bleeding (Tannin Precipitation)：Composite decking is made up of 60 percent wood flour and 30 percent HDPE protecting it. Despite the polymer shell, the wood flour remains partially exposed and leads to the release of tannins – natural substances found in wood. On contact with water, the tannins leach into the surface and stains appear.

2. Environmental & External Pollution: Long-term exposure to cooking fumes, acid rain corrosion, or prolonged adhesion of airborne dust on the board surface will cause these contaminants to mix with minerals in water, gradually depositing to form visible water stains.

Why is the appearance of stains not a problem?

Tannin stains are a natural process that confirms the naturalness of the material. It does not affect the strength or durability of the patio.

Over time, these stains become less visible and do not indicate damage to the material.

Composite decking Care

To maintain the aesthetic appearance of your decking, we recommend :

1. Clean with mild soapy water

2. White vinegar trick for stains (perfect for hard water limescale and light tannin marks)

3. Grab a dedicated WPC cleaner (for those stubborn tannin water stains)

We do not recommend using scrapers and brushes with steel pile, which will damage the top layer of the decking.

Composite decking will be the perfect choice for your patio due to its many benefits: strength, durability and minimal cleaning time. If properly maintained, you will keep its appearance for many years, providing comfort and cosiness on your terrace. 

Read our guide on what is composite decking to learn how WPC decking is made, its main advantages, lifespan, maintenance requirements and common applications.