We don’t need to tell you that this has been a very wet year so far. With just a few exceptions, the weather can only be described as extremely unsettled. Unfortunately, this isn’t a one-off. The climate is changing and this will impact many aspects of our lives. In this article, we focus on how to protect Shou Sugi Ban® timber cladding from changes to the weather.
Weathering & Wood
Timber is a natural, organic material which has been used for architecture, garden landscaping, outdoor furniture and many other exterior applications. When untreated and exposed to sunlight and rain, timber will weather. This is a term describing a change of colour to silvery grey, which is caused by oxidisation.
Differential weathering is where uneven changes occur due to the position of timber cladding and other wood features. For example, a south-facing wall experience greater exposure to sunlight. Therefore, timbers change colour at a faster rate than those on an east or north-facing wall. What’s more, areas protected by gables, soffits and other features will weather at a slower rate.
In addition, timber is a hygroscopic material, which means it is impacted by moisture. Damp environments cause the wood to expand and it contracts when the moisture dries out. This doesn’t necessarily reduce the structural integrity of the timber. However, installers need to allow for some degree of movement to avoid warping.
For these reasons, most exterior timbers are treated to protect against the elements and minimise weathering. These treatments include surface applications of wood oils, varnishes and paints. An alternative method of preserving timber is controlled charring. Originating in Japan, this technique is known as Yakisugi.
Yakisugi: The Art of Timber Preservation
With Yakisugi, the application of heat alters the cell structure and draws out the natural resins. These form a protective layer that is effective at making the timber more resilient to the effects of weathering and moisture. This blackened timber has a desirable aesthetic and increased durability.
The resilience of charred timber cladding has been put to the test in several studies*. These include exposing the wood to exposure testing, along with freeze and thaw cycle testing. Fortunately, the results confirm that the charring process improves performance. It also greatly reduces signs of weathering and changes to the surface colour.
Finishing Oils for Shou Sugi Ban® Timber Cladding
Japan’s climate is not too different from what we experience in the UK. Both countries experience seasonal changes, with colder and warmer months. So, when we discovered Yakisugi several decades ago, we decided to master the art of timber preservation in the UK. Inspired by tradition, we tried and tested a variety of timbers and techniques to create Shou Sugi Ban®.
We know that no finishing application is used in Japan. However, we use a sealing oil on our timber cladding. This enhances the longevity and appearance. It also reduces the rub-off onto hands when the timber is touched.
Climate Change & Shou Sugi Ban®
The climate is changing and we are experiencing more ‘exceptional’ weather conditions. The Met Office confirms that April in the UK was one of the wettest on record since 1836**. Storm Kathleen hit, causing some regions to experience flooding. Meanwhile, you know as well as we do that sun levels were lower than average. And, that remained true throughout May.
Unfortunately, we are likely to experience more unsettled and unpredictable weather in the future. With this in mind, work is underway to understand how to make the built environment more resilient to climate change. We need to reconsider architecture and building materials to ensure they are fit for the future.
In terms of Shou Sugi Ban®, we have seen that more regular reapplications of finishing oil are effective at protecting timber from persistent rain and occasional periods of strong sunlight. Charred timber cladding remains a lower maintenance option compared to other wood finishes. However, applying a penetrating oil will help to maintain the appearance and longevity.
Our Advice & Summer Offer
Are you keen to better preserve your Shou Sugi Ban® cladding? If so, we are happy to advise. We’ll recommend the most appropriate solution depending on the timber and finish that you purchased from us. Please send your questions and images to admin@exterior.supplies.
A dry spell is the best time to recoat your timber cladding. Therefore, we are offering customers who contact us a £5 discount on any orders of oil purchased from our online shop before Friday 20th September. We can’t stop climate change, but we can help protect your timbers from weathering.
*https://pure.coventry.ac.uk/ws/portalfiles/portal/37619300/Matthew_White_MScR_Pure.pdf
** https://blog.metoffice.gov.uk/2024/05/01/a-wet-and-dull-april/