Oak is a popular choice for various woodworking projects, primarily due to its durability, beauty and natural characteristics. However, when it comes to painting oak, there are some considerations to keep in mind. Today, we’re delving into the reasons why it can be problematic, discussing factors such as moisture content, tannins, adhesion issues and wood movement. Additionally, we’ll provide expert advice on achieving the best results when painting oak, including recommendations on drying and stabilising the wood. So, if you’re planning a project involving oak and are considering painting it, read on to learn more.
What is the difference between green and air-dried oak?
When it comes to oak, understanding the differences between air-dried and green oak is essential. Air-dried oak refers to wood that has been left to naturally dry in the open air over a period of time. This slow drying process allows the moisture content of the wood to gradually decrease, resulting in a more stable and workable material. On the other hand, green oak refers to freshly cut wood that has not undergone any drying process. It retains a higher moisture content, making it more prone to movement and shrinkage as it dries. The key distinction between the two lies in their moisture levels and stability, with air-dried oak being the preferred choice for projects that require a more predictable and less prone to warping material.
Green and air-dried oak has a number of applications, but there can be issues when it comes to painting.
What is air-dried oak used for?
Air-dried oak finds extensive use in various woodworking and construction applications. Its unique characteristics and reduced moisture content make it a preferred choice for many projects. Air-dried oak is commonly utilised in furniture making, where its stability and strength lend themselves well to crafting durable and long-lasting pieces. It is also sought after for interior trim work, such as mouldings, panelling, and flooring, as its lower moisture content reduces the risk of warping and movement over time.
Additionally, as timber suppliers covering West Sussex and the surrounding areas, we often find that air-dried oak is popular for outdoor applications like decking, fencing, and timber framing, thanks to its natural resistance to decay and durability in different weather conditions. Its beautiful grain patterns and warm aesthetics make it a desirable option for architectural features, decorative elements and bespoke woodworking projects.
What is green oak used for?
Despite its higher moisture content and propensity for movement as it dries, green oak has its own set of applications and advantages. It is commonly employed in traditional timber framing and construction, where its natural strength and flexibility are valued. Green oak beams and structural elements can be shaped and joined while the wood is still green, allowing for intricate designs and craftsmanship. This makes green oak a preferred choice for timber frame buildings, barns and other structures where the characteristic look of exposed, seasoned oak is desired.
It is also used in outdoor projects, such as garden structures, pergolas and rustic furniture, where the wood’s natural weathering and eventual development of cracks and splits add to its charm and character. Green oak is favoured by many timber tradesmen who appreciate the unique qualities it brings to their creations, showcasing the beauty of freshly cut, unseasoned wood.
Usually, oak is left unfinished and gradually becomes the traditional silver-grey colour with exposure to UV light.
Can you paint green or air-dried oak?
Normally oak is left unfinished and gradually becomes the traditional silver-grey colour with exposure to UV light. While it’s possible to paint green and air-dried oak, it’s beneficial to take the points below into consideration before taking the plunge into using green or air-dried oak in your timber project.
Moisture content
Freshly sawn oak contains a high moisture content. It needs time to dry and stabilise before any finishing treatments, including painting, can be applied. If you paint oak that is not properly dried, the wood may continue to release moisture, leading to issues such as warping, cracking, or peeling of the paint.
Tannins
The high tannin content in oak is one of the reasons it is so durable. Oak works well for outside applications, as well as inside, and in some soil conditions lasts for over 10/15 years depending on ground contact. When oak is freshly cut, the tannins (natural substances found in the wood) can migrate to the surface, causing discolouration or staining of the paint. This can result in uneven or blotchy paint finishes.
Adhesion issues
Due to the high tannin content and moisture in fresh-sawn oak, it may be challenging for the paint to adhere properly to the surface. Paint may not bond effectively, leading to poor adhesion and an unsatisfactory finish. The paint may peel or chip off over time.
Wood movement
Oak is a natural material that expands and contracts with changes in humidity and temperature. Freshly sawn oak is more prone to significant movement as it dries and adjusts to its environment, often developing cracks and splits that give it huge character. This movement can cause stress on the paint layer, leading to cracks or flaking.
Our advice when working with air-dried and green oak
We have over 155 years experience working with timber at W.L. West & Sons Ltd, we have a wealth of experience which has informed our practise and advice.
To achieve the best results when painting oak, it is generally recommended to allow the wood to dry and stabilise for several months or until the moisture content reaches an acceptable level (around 12% to 15%). This allows the tannins to leach out and the wood to settle, reducing the risk of moisture-related issues and ensuring better paint adhesion and durability. It’s advisable to consult a professional or follow specific guidelines for preparing and painting oak to achieve optimal results.
One product we have found to be an excellent product to coat oak is Roxil. It is a very useful product to have in your armoury if needed as it creates an invisible waterproof barrier – but bear in mind it’s a silicone product which cannot be decorated over. It can slow UV colouring, but the oak will still go the classic silver-grey colour in time. Roxil can also slow the drying process to give less fissuring and end splitting (cross sectional end sealing is key for all timbers – especially oak).
If you need to seek further advice or source high-quality oak for your upcoming timber project, get in touch to see how we can support you today.
WL West & Sons Ltd is a timber merchant and sawmill business with 150 years of experience. We provide a wide range of air-dried oak and kiln-dried oak timber products and supplies. We also build and install custom projects for our customers.
Our wood products, building materials and certified wood are manufactured and sold with the endorsement of forest certification and the Forest Stewardship Council FSC
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