Timber cladding weathering: everything you need to know

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Timber is an organic, natural material which when left uncoated, will weather to a beautiful silver-grey colour over time. Weathering, or oxidisation, is caused by sunlight, rainfall and changes in moisture content and is one of the main processes that affects timber. This blog will discuss the causes, benefits and solutions that assure weathering is considered and utilised to its maximum benefit.

Scotlarch® cladding naturally weathered to a grey tone | Sandbank, Iona | Mary Arnold Forster Architect

How timber weathers

Wood is a hygroscopic material, which means it has a tendency to take and hold moisture from its surroundings. This process of expanding and contracting (taking in and releasing moisture) from both the air and from rainfall is a key element in the weathering process, and is what causes less stable, low-quality timber to ‘cup’. Natural weathering does not affect the structural integrity or performance of timber, merely the appearance.

This visual element of the weathering process is the colour change from the timber’s original tone to a grey, silvery tone. This occurs when sunlight’s UV rays break down the lignin in the surface wood cells. Depending upon the environment, this process can take from a few months to several years.

The resulting weathered grey colour is an organic yet modern tone which is frequently the desired aesthetic for timber cladding. This is because it provides a neutral, balanced facade which can be combined with other building materials with little effort.

Scotlarch® cladding before weathering | Culloden | Hoskins Architects
Scotlarch® cladding in its weathered state | Culloden | Hoskins Architects

Weathering patterns and differential weathering

When the weathering process is understood both aesthetically and scientifically, architects, contractors and domestic customers can utilise this organic process and consider it as part of the overall project rationale. Depending on the aspect and structure of a building, timber cladding will always weather to a grey tone over time. The weathered grey tone can be selected as the ‘final’ finish of the facade and be left to weather in relation to the rest of the building. This was previously a more rustic design philosophy, but in recent years the silvery sheen of weathered timber cladding has become a more common and desired finish on modern projects.

Differential weathering refers to weathering that occurs unevenly due to the design of a building. South and West facing walls weather faster due to higher exposure to sunlight, with East and South facing walls weathering more slowly. This is further influenced by overhangs and soffits, which can produce even more differential weathering. When it comes to rainfall and moisture, areas of a building’s facade which are wetter or more prone to wind-driven rain weather much faster than drier areas. These combined influences can create weathering that is uneven or even unsightly.

The solution to differential weathering? Bring in SiOO:X.

SiOO:X Wood Protection is a water based, natural and non-toxic coating which eliminates differential weathering and produces a consistently weathered look at a much faster rate.

SiOO:X is a patented silicon technology which is applied in two parts; Wood Protector, followed by Surface Protector. Wood Protector penetrates the wood and Surface Protector seals the wood’s surface. The coating reacts with the timer, curing over a short period of time, which produces the finish.

SiOO:X Original is a clear coating which achieves a consistent tone in around 10-16 weeks. For immediate colour, SiOO:X Light Grey or Mid Grey can be applied, giving a consistent weathered look from the onset. All SiOO:X products develop over time, with a final colour being reached after 2-3 years. SiOO:X results in a beautifully even façade, with a consistently weathered appearance.


Scotlarch® cladding coated with SiOO:X Original
SILA Select® cladding coated with SiOO:X Mid Grey
Thermopine® cladding coated with SiOO:X Mid Grey | Eyemouth Fishmarket project | Galmstrup Architects
Read more about using SiOO:X Wood Protection on your project here.

Products Used


Our Scottish Larch (Scotlarch®) is sourced locally and a cost-effective cladding solution.
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Thermally modified Scandinavian Scots Pine, modified using only heat and steam.
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SiOO:X Wood Protection eliminates differential weathering and provides a consistently weathered tone.
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