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

SILA Select® Cladding Factory coated with SiOO:X (mixed widths) Penton Architects | Bruce Hemming Photography

What is SiOO:X?

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 the gallery above which shows examples of SiOO:X coated Scotlarch®, SILA Select® Siberian Larch and Thermopine®.

The Swedish surface coating impregnation system which utilises revolutionary silicate technology offers timber with a consistently weathered appearance at an accelerated rate. Russwood are proud to have been working in collaboration with SiOO:X for over 5 years, as Premium UK Specification Partners and Distributors.

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 the surface fibres into the wood cells 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.

1 year weathering North facing
SiOO:X v’s uncoated

SILA A/B® RW014 Factory Coated with SiOO:X Mid Grey | Fiddes Architects | Nigel Rigden Photography
SILA Select Siberian Larch RW014 Factory Coated with SiOO:X Mid Grey | Fiddes Architects | Nigel Rigden Photography

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 Skimmed 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 at our modern in-house coating facility. Russwood adhere to ISO 9001 Quality Management System which ensures 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.

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, can be purchased through our online shop. Guidelines on SiOO:X application can be found here and a list of FAQs can be found at the bottom of this page.

SILA Select® Siberian Larch factory coated with SiOO:X Light Grey (100 & 75 x 25mm) | Laura Patten Architects | Will Eckersley Photography
SILA Select® Siberian Larch factory coated with SiOO:X Light Grey (100 & 75 x 25mm) | Laura Patten Architects | Will Eckersley Photography

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 CoatingOn-site SiOO:X Application
ConsistencyConsistently even machine applied coating ensures a flawless finish. Scientifically proven to provide a more uniform coating applicationDifficult to monitor quantity and consistency of coating applied, potentially leading to an inconsistent finish
Initial CostsWe charge a set price, quoted upfront, for coated cladding; this includes preparation, coating, drying, protective wrapping, storage and deliveryLabour, 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 & Clean-upTimber arrives on-site pre-coated, meaning no preparation or clean upProtective 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 ApplicationCoating is applied under factory conditions, to timber which is dried to it’s optimum moisture content. This means that weather is irrelevant and can be factory coated year roundVariables to consider when using traditional brush application include temperature, sunlight, rain, general moisture and long spells of changeable UK climate
Surface preparationWe recommend Microtex® or Skimmed surface finishes when for application of SiOO:X, but at a minimum a dressed board should be sanded to 60 grit prior to application of SiOO:X to allow the treatment to penetrate the surfaceDressed profiled boards must be sanded on site prior to onsite application of SiOO:X. Increasing time labour requirements considerably
SealingBoards 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, in turn reducing durability
Aesthetic PropertiesConsistently applied factory coating ensures a flawless finishInconsistencies in application may lead to a less-than-perfect end result
Advice & delivery
Time from Order to Finished ProductPlease check with our Sales Team for current lead times.After delivery, completion should be entirely dependant on weather conditions and labour availability
Advice AvailableTimber, detailing, profile and fixing advice is part of the high standard Russwood serviceThis will be dependant on the timber cladding experience of the on-site team

VG SILA Cladding profile RW212 factory coated with SiOO:X (during curing process)

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. 

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

Frequently Asked Questions

Can I buy SiOO:X from Russwood online?

Yes, you can purchase SiOO:X through our online shop. We sell SiOO:X part 1- Wood Protector in 3 and 5 litre tubs. SiOO:X part 2- Surface Protector is also available in 3 and 5 litre tubs.

How do I apply SiOO:X by hand?

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

Does SiOO:X coated timber require maintenance?

SiOO:X coated timber is largely maintenance free, with an optional re-coating cycle of between 10-15 years. In many instances, exposed timber will have taken on a naturally weathered appearance by this time and therefore re-application is not necessarily required. If surface dirt or algae form on a SiOO:X treated surface over time, they can be cleaned off using a solution of SiOO:X Maintenance Wash and water. Maintenance wash is available through our online shop.

For decking, which is subjected to very severe wear in comparison to cladding, it is recommended to apply an additional coat of Surface protector after 1-2 years. Re-application of both Parts 1 and Part 2 may be considered after 4-5 years. As with any deck, SiOO:X treated decking should be cleaned regularly to remove surface dirt and debris.

If I order cladding pre-coated in SiOO:X Original, what colour will it be when delivered to site?

Immediately after application of SiOO:X Original (not the pigmented Light Grey or Mid Grey), the colour can range from the wood’s original colour, to a dark apple-juice brown. The colour of the boards may also vary depending on the tannin content. This colour variation evens out quickly and, over a period of 10-16 weeks once exposed to moisture and humidity in the atmosphere, the timber will lighten and develop a uniform appearance as the SiOO:X cures. The full curing process of SiOO:X Original takes up to 2 years, by which time the timber will be a pale, driftwood grey colour.

How would you describe the end colour of SiOO:X Original and pigmented versions?

SiOO:X Original coated timber will weather to a consistent pale driftwood appearance. SiOO:X is also available in a Light Grey which is a cool grey driftwood colour and Mid Grey which will initially be a soft blue/grey colour weathering to a natural mid grey colour over the course of 16 weeks.

Can I order SiOO:X coated timber samples?

From our experience the curing process requires exposure to the elements for approximately 8-16 weeks for the timber to have lightened appreciably. Unfortunately we do not have sufficient space or resource to allow timber samples to weather fully – we simply wouldn’t be able to meet demand.

Can I use SiOO:X on both sawn-face and dressed-face timber?

Russwood strongly advise the SiOO:X is applied to Skimmed or a Microtex® surface to ensure correct volume of application. If SiOO:X is to be used on smooth dressed surfaces, prior to application, the timber should be sanded with a 60 grit sand paper to aid application levels.

Do I need to cover adjacent surfaces when I am applying SiOO:X?

SiOO:X products may leave deposits if spilled onto metallic surfaces or glass. These deposits can be difficult to remove therefore it is important that these areas are masked and protected. If spills occur, clean up quickly with a wet cloth.

Can SiOO:X be used on all species of timber?

SiOO:X can be used on most timber species. Please contact our team of Cladding and Decking Advisors for further information regarding suitability of application with Russwood products. In Sweden, SiOO:X have extensive successful experience of application on pressure treated softwood decking. Russwood’s experience with SiOO:X is with testing and assessing it on timber species and surfaces finishes in the UK’s maritime climate.

Will all areas take on the same tone, regardless of exposure to rain and other weathering factors?

Yes, however extremely sheltered areas (for example, under large overhangs) may take longer to turn fully grey. These areas can be soaked with water intermittently to speed up the curing process. This may be repeated several times as required.

Can I use SiOO:X in conjunction with fire retardants?

Currently, SiOO:X has not been approved for use in conjunction with fire retardants.

Species Suitability

The following species are suitable for coating with SiOO:X