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Russwood have been appointed as premium UK specification partners of SiOO:X, the Swedish timber impregnation system which utilises revolutionary silicate technology. We are excited by this collaboration and believe it to be a major step forward in offering timber with a consistently weathered appearance at an accelerated rate. SiOO:X is a patented wood surface modification which is applied in two parts (Wood Protector & Surface Protector) and is suitable for use on the majority of our cladding species, as seen in our SiOO:X Gallery which shows examples of SiOO:X coated Scotlarch®, Siberian Larch and Architect Select® Western Red Cedar cladding. 

How does SiOO:X work?

SiOO:X is a patented Silicon technology, applied in two parts. SiOO:X Wood Protector (Part 1) is applied first - it penetrates deep into the fibres of the cell walls where it forms a network of silica crystals, creating a barrier which is bonded to the surface. A further application of SiOO:X Surface Protector (Part 2) is then applied which binds with the Wood Protector and prevents water penetration.

Following application, SiOO:X cures by reacting with atmospheric carbon dioxide and moisture to form an insoluble and flexible silica network within the timber surface. The formation of this silica network toughens the surface of the timber and forms an effective barrier against insect attack and rot.

In addition to the protective benefits gained, as the mineral silicate cures over time it will start to turn the timber a beautifully even silver / greyish tone within 10-16 weeks. From our experience, boards will initially go darker and then lighten over time. The end result is a façade with a consistently weathered, light grey driftwood appearance.

How a façade weathers is dependant on the location, design and the species of timber used. Facades which have not weathered as evenly as expected may be deemed unsightly due to inconsistent colouration. A common example of this is when boards protected by the building’s eaves maintain their natural colour whilst the exposed areas of the building weather down to a grey colour. SiOO:X is a solution to this problem. In the months following application all boards will turn the same tone regardless of their colour and exposure to the elements prior to application, resulting in a desirable, consistently weathered look.

SiOO:X colours

While the curing effect of SiOO:X takes 3 to 4 months to develop it’s silver grey appearance, SiOO:X Mid Grey and Light Grey versions have been developed to give an immediate and long lasting colour to the timber. SiOO:X Mid Grey gives a soft, muted grey colour while the Light Grey version gives a very pale, almost white colour to the timber. Both of these variations have been developed to work in harmony with the curing effect of SiOO:X to give their own versions of lighter and darker weathered colours.

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

SiOO:X can be applied to both new and existing facades

New facades

We can produce cladding which has been pre-coated with SiOO:X. By treating the timber under factory-controlled conditions. The application will be of a consistently high standard and therefore we would always recommend factory coating over traditional brush application for new-build projects. The additional benefits of factory coating are described in the ‘factory coating v’s Brush application’ table, below. For smaller domestic projects, brush application may be the most feasible option and we would recommend contacting our technical team to discuss your options.

Existing facades

We also supply SiOO:X for traditional on-site brush application. Typically this is used on smaller domestic projects or existing facades which have not weathered as evenly or as quickly as anticipated. Containers of 3 and 5 litres, as well as 250ml sample pots, can be purchased through our online shop. Guidelines on SiOO:X application can be found here.

Factory coating v’s Brush application

We have the ability to coat timber in-house under factory controlled conditions, meaning that highest quality standards can be consistently achieved by our specialist coatings team. Factory coating comes with a number of advantages over traditional brush application, as outlined in the table below;


Russwood factory-coating

On-site SiOO:X application



Consistently even coating guarantees a flawless finish. Scientifically proven to provide a more uniform coating application

Difficult to monitor quantity and consistency of coating applied, potentially leading to an inconsistent finish


Initial costs

We charge a set price, quoted upfront, for coated cladding; this includes preparation, coating, drying, storage and delivery

Labour, coating equipment and scaffolding (if required) costs will be incurred, plus the potential cost of project delays due to adverse weather   conditions should be taken into consideration

Preparation and clean-up

Timber arrives on-site pre-coated, meaning no preparation or clean up

Protective masking or taping may be required to vulnerable surfaces pre-application. Clean-up from spills or etching may be required post-application. Both lead to increased labour costs

Finish & Durability

Conditions required for application

Coating is applied under factory conditions, to timber which is dried to it’s optimum moisture content. This means that weather is irrelevant

Variables to consider when using traditional brush application include   temperature, sunlight, rain and general moisture

Sanding (For machined/profiled boards)

Boards are 60 grit sanded prior to coating, opening up the pores of the timber and allowing for greatly improved take-up of the SiOO:X

We would recommend sanding machined/profiled boards prior to onsite application of SiOO:X. Increasing labour requirements and time onsite 


Boards are coated on all four sides, reducing moisture ingress 

Often only the front face is coated, leaving the back and edges of the boards uncoated and therefore exposed to the elements, therefore reducing durability

Aesthetic properties

Consistently applied factory coating guarantees a flawless finish

Inconsistencies in application may lead to a less-than-perfect end result

Advice & delivery

Time from order to finished product

Please check with our Sales Team for current lead times.

After delivery, completion should be entirely dependant on weather conditions

Advice available

Timber, detailing, profile and fixing advice is part of the high standard Russwood service

This will be dependant on the timber cladding experience of the on-site   team


In the run up to our launch of SiOO:X we carried out extensive tests at our sawmill and production site. In addition to this, we have an independent piece of research underway in conjunction with Napier University’s Centre of Wood Science and Technology. Some images of our own research and outcomes can be seen in the revolving slides above.

Sustainable Credentials

SiOO:X contains only natural, non-toxic, recyclable ingredients and complies with EU test proceedings EN 46 and EN113. Additionally, all of the timber we supply is FSC® or PEFC certified which ensures the chain of custody of our timber is controlled from forest through to finished product.

Additional Benefits 

As a wood surface modification system, SiOO:X also brings significant protection properties through the formation of a silicon network which combines water repellent properties with the strengthening of the timber surface. 

Brush Application Instructions

Detailed instructions on how to apply the two-part SiOO:X system can be downloaded here.

Estimated coverage for brush coating

SiOO:X Wood Protector: 1st coat 6-8 m2/litre; 2nd coat 10-12m2/litre

SiOO:X Surface Protector: 8-12 m2/litre


SiOO:X coated timber can be regarded as largely maintenance free and can be left for between 10-15 years before re-application may be considered. In many instances, timber will have taken on a naturally weathered appearance by this time and therefore reapplication is not necessarily required.

Timber decking or very low level cladding may gather dirt, particularly after winter. The surface can be cleaned with SiOO:X maintenance wash or other mild detergent, brushed and then rinsed. Guidelines on SiOO:X maintenance can be found here. 

Frequently Asked Questions

For frequently asked questions regarding SiOO:X, click here.