Everything you need to know about SiOO:X

4 min read


Achieve a weathered look without the wait by the application of SiOO:X, a Swedish surface coating impregnation system which uses advanced silicate technology to provide a consistently weathered appearance to timber cladding at an accelerated rate.

Scotlarch® Cladding factory coated with SiOO:X | Line Architecture
Scotlarch® Cladding factory coated with SiOO:X | Line Architecture

What is SiOO:X?

SiOO:X is a Swedish wood surface modification designed for external timber which is applied in two parts (Wood Protector & Surface Protector).

The patented surface coating impregnation system utilises revolutionary silicate technology, which penetrates the wood giving protective benefits for the timber whilst developing a beautiful silver grey colour to the wood.

What are the benefits of SiOO:X?

SiOO:X penetrates into the wood fibres of the timber surface and cures to form a flexible silica network within the timber surface. The silica network fuses to the wood cells, reinforcing and toughening the timber surface while forming an effective barrier to invasive insects and decay fungi. 

In addition to the protective benefits brought by SiOO:X, the system gives the wood a light weathered grey appearance as it cures. This colour change happens very uniformly around a building, avoiding the potential issues of differential weathering rates on north/south facades, and mitigating the potentially patchy effects which overhangs, eaves etc can have on uncoated timber.

By contrast, uncoated timber may take a decade or more to weather in very sheltered areas – some areas might never weather properly if they are very covered – and this can be an aesthetic concern for some customers.

SiOO:X is very popular for customers who desire the weathered grey look for their project but want it to happen quickly and uniformly around the building.

The full curing time of SiOO:X is around two-three years, however, results are noticeable after around 6-8 weeks. The most dramatic colour shift happens within the first six months or so, after which time the timber will already have developed a uniform silvered aesthetic. 

SiOO:X-coated vs natural
1 year weathering North facing
SiOO:X (Left) vs uncoated (Right)

The end result is a façade with a consistently weathered, light grey driftwood appearance.

The stunning Narula House project, situated on a river Thames tributary, is an excellent showcase for the beautiful and uniform aesthetic of SiOO:X. This project uses Russwood’s SILA Select® Plus grade Siberian Larch, factory coated with SiOO:X Original.

SILA Select Plus (95 x 20mm) Factory coated with SiOO:X Original | John Pardey Architects | James Morris Photography
SILA Select Plus (95 x 20mm) Factory coated with SiOO:X Original | John Pardey Architects | James Morris Photography

What colours does SiOO:X come in?

While the curing effect of SiOO:X Original takes several months to develop, and 2-3 years to reach its final tone, SiOO:X Mid Grey and Light Grey versions have been developed to give an immediate colour to the timber. The pigment additives in both versions work in harmony with SiOO:X system, and these versions accent the cured colour of the SiOO:X treatment for a long-lasting and uniform appearance.

SiOO:X Mid Grey and Light Grey have been developed specifically for use with fine-sawn or Microtex® surfaces and, due to the mixing and application requirements of the pigmented products, are available as factory-applied coatings only.

Thermopine® Cladding Microtex® factory coated with SiOO:X Mid Grey (Left) and Light Grey (Right)

SiOO:X Mid Grey

SiOO:X Mid Grey gives a soft muted grey hue, similar to a nice weathered example, which fits very naturally into any landscape. This private home in Devon is a prime example of the effect of SiOO:X Mid Grey, immediately helping the new build house and its Siberian Larch cladding settle into the surroundings.

SILA Select® Cladding factory coated with SiOO:X Mid Grey | Private House, Devon
SILA Select® Cladding factory coated with SiOO:X Mid Grey | Private House, Devon
SILA Select® Cladding factory coated with SiOO:X Mid Grey, fixed with L-GoFix® screws
SILA Select® Cladding factory coated with SiOO:X Mid Grey, fixed with L-GoFix® screws

The use of timber cladding on this project in Kent would usually be a challenging design from a weathering perspective. The large overhangs and sheltered areas of timber would normally cause significant differences in the weathering of these areas. SiOO:X Mid Grey works around this issue and has provided the project with a wonderful consistency in this example.

SiOO:X Light Grey

In contrast, the Light Grey version brings a more striking pale driftwood colour, which can really make a project stand out.

This project by Gerry Robb Architects is one of my favourites. The image really speaks for itself. The project showcases the architecture of the building, the stunning locations in which it is set, the beauty of Russwood’s SILA Select® grade Siberian Larch, and the striking tone of the SiOO:X Light Grey.

SILA Select® Cladding Off-Sawn, factory coated with SiOO:X Light Grey | Gerry Robb Architectural Design | Brudon Joinery Ltd
SILA Select® Cladding Off-Sawn, factory coated with SiOO:X Light Grey | Gerry Robb Architectural Design | Brudon Joinery Ltd

What’s the best way to apply SiOO:X?

We recommend that SiOO:X is applied in factory conditions where possible, where machine application methods and controlled drying conditions allow for the best possible consistency of application and coating penetration.

SiOO:X is applied as a flood coating system, and works most effectively where it can penetrate the timber more deeply, and with maximum saturation. Smooth surfaces should be sanded with no finer than 60 grit prior to application to open up the surface, but for best results, Russwood recommend using a fine-sawn or Microtex® surface with SiOO:X.

Application of SiOO:X can be carried out on-site with due care by following the detailed application instructions.

SiOO:X Original can be bought through our online shop for application on-site. SiOO:X Original, Mid Grey and Light Grey can be factory-applied to Russwood’s timber cladding. For more information on our factory SiOO:X coated cladding please contact our sales team.


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