Natural weathering of wood: 4 Things to Know and Consider

Let’s take a closer look at how and why wood colour changes, the environmental and architectural factors that influence the natural weathering process, and the different approaches you can take to either slow down or accelerate this natural transformation.
Spoiler alert: Whether you’re drawn to the natural silver-grey patina, want to preserve the original brown tone, or prefer to add colour – with the right approach, all options are entirely within reach.

1. The main drivers of colour change

 

• UV radiation breaks down lignin on the surface of the wood, leading to surface oxidation and eventually causing the wood to turn grey.
• Moisture and rain act as key accelerators. Rain supports the process by washing away degraded lignin, essentially cleaning the surface and contributing to a more even patina.

The rate and evenness of colour change vary significantly depending on how sunlight and moisture interact in a given environment. In climates where sun and rain occur in a well-balanced ratio, wood tends to weather consistently and beautifully. Dry but sunny areas with good airflow also support fairly even greying. In contrast, shaded and humid locations with little direct sunlight may result in uneven or patchy silvering.

In the last named conditions, limited airflow and constant moisture can encourage organic buildup – such as dirt, mould, or moss – which may darken the surface and interfere with the natural weathering process. While this doesn’t affect the structural integrity of Thermory’s thermally modified wood, it can alter the appearance over time. To help maintain a clean and even look, we recommend gently cleaning the wood surface at least once a year, especially in areas prone to high humidity or shade.

Check out our maintenance guide for tips and techniques for cladding and decking.

2. Architectural factors that may affect colour evolution

These effects are usually most noticeable during the early stages of weathering. Over time, the differences tend to soften and in many cases, they become part of the wood’s natural, character-rich aesthetic. However, design elements with poor drainage that trap water or allow moisture to linger should be avoided, as they can lead to organic buildup such as dirt, algae or moss.

Overhangs, eaves, and covered terraces can block both sun and rain, keeping surfaces drier and less exposed to UV. These areas tend to grey more slowly, often creating visible contrast with surrounding wood.

Window sills, water locks, and horizontal trim details can redirect or trap moisture. Poorly angled sills may cause water to splash back onto the cladding, while design elements that lead to constant dampness can promote organic buildup or surface staining, which may interfere with the even development of the natural silver-grey patina.

Facade orientation and shape also matter. West- and south-facing walls typically grey faster due to higher sun exposure. Angled or curved surfaces may catch light unevenly throughout the day, leading to subtle tone variations across the facade.

3. Wood species and natural variation

It’s also worth noting that each wood species weathers a little differently. The rate and tone of greying can vary depending on how the material reacts to UV exposure and the elements. For example, Thermory thermo-ash, -pine, -spruce and -radiata pine all develop a silver patina over time, but each follows its own timeline – and with subtle differences in hue and depth.

These variations are part of the beauty of real wood. When planning your project, it’s helpful to understand how your chosen species is likely to evolve so that you can match your aesthetic expectations with the natural behaviour of the material.

Thermo-spruce

Thermo-ash

Thermo-radiata pine

Thermo-pine

4. When you want more control over the final look

Maybe you live in a demanding climate. Maybe you want to preserve the original look. Maybe you’d like to be more creative with colour – or simply prefer to stay in control of the final result. Whatever the reason, you don’t always have to wait for nature to do its thing.

With Thermory’s Vivid Collection, you can choose finishes that offer a pre-weathered look, protect the original tone, or add colour with confidence – all while keeping the benefits of thermally modified wood.

Vivid Opaque

Vivid Oiled

Vivid Translucent

Vivid Silvered

Final Thoughts

Wood is a natural material – and that’s exactly what makes it so special. It responds to its surroundings, changes with time, and adds a sense of warmth and authenticity to any design. Its evolving colour is part of its charm, telling a story that’s shaped by light, weather, and life itself. Whether you choose to embrace these natural changes or take steps to guide the process, there’s no wrong approach – just the one that best fits your vision.