Why has my timber faded?
Why Timber Fades When Exposed to UV Light and Weather
Timber is one of the most beautiful and versatile natural building materials. Whether used for decking, cladding, fencing, or outdoor furniture, its warm tones and grain patterns bring a timeless, organic appeal to any space. But if you've ever noticed timber fading, turning grey, or losing its original colour after prolonged exposure to the elements, you're witnessing a natural weathering process—primarily driven by ultraviolet (UV) light and moisture.
Let’s explore what causes timber to fade, and how you can protect it to extend its life and preserve its appearance.
The Role of UV Light in Timber Fading
The sun emits ultraviolet radiation, which is invisible to the human eye but has a powerful impact on organic materials like timber. When timber is exposed to UV light:
Lignin breakdown begins: Lignin is a complex organic polymer found in the cell walls of wood. It acts like a glue, binding the fibres together and giving the wood its strength. UV radiation breaks down this lignin over time.
Surface degradation occurs: As the lignin breaks down, it leaves the surface of the timber more porous and weak, making it easier for other environmental factors to take a toll.
Colour change happens: Lignin has a natural colour that contributes to the rich hues of timber. Once it starts to degrade, the timber loses its colour, often turning a silvery-grey. This is most noticeable on timbers like cedar, teak, and redwood.
Weather and Moisture: Partners in Fading
While UV light initiates the breakdown of timber, weather elements like rain, humidity, and wind help accelerate the process:
Moisture cycles cause swelling and shrinking: Timber absorbs moisture from rain or humidity and dries out when exposed to the sun. These repeated cycles of swelling and shrinking can lead to cracking, splitting, or cupping, exposing fresh wood to UV damage.
Leaching of natural oils: Many timbers contain natural oils and tannins that contribute to their colour and durability. Rain can leach these out over time, especially if the timber isn't sealed.
Surface erosion: Wind and water gradually erode the weakened surface fibres, which removes even more of the timber’s original colour and texture.
Is Fading Bad for Timber?
Fading doesn’t mean your timber is damaged. The silver-grey patina that develops is purely cosmetic and is often desired for its rustic or weathered appearance, especially in architectural design.
How to Protect Timber from Fading
If you want to maintain the timber’s original appearance or protect it for longevity, consider the following:
Apply UV-protective finishes: Use wood oils, stains, or sealants that contain UV inhibitors to slow down the degradation of lignin.
Regular maintenance: Clean and reapply protective coatings as recommended—typically once or twice a year depending on exposure.
Design for protection: Incorporate shading, overhangs, or water-shedding features into your design to limit direct exposure.
In Summary
Timber fades when exposed to UV light and weather due to the breakdown of lignin, leaching of natural oils, and erosion of surface fibres. While the silvering effect is natural and harmless in many cases, proactive protection and maintenance can preserve both the beauty and integrity of your timber for years to come.
Whether you prefer the rustic charm of weathered wood or want to keep your timber looking fresh and vibrant, understanding the causes of fading helps you make informed decisions for your outdoor timber projects.
