Green oak is the term used to describe oak timber that has been cut between three and eighteen months after the tree has been felled. It is also known as Fresh Sawn oak for obvious reasons and is used without any drying or preservative treatment. In this case, green refers to the freshness of the product rather than its appearance as there is no green hue to the wood itself.
Working With Green Oak
Unlike other types of timber that need chemical treatment to safeguard against weather damage or decay, freshly sawn oak can be used for interior or exterior applications without any treatment. This lowers the cost of the product and diminishes the environmental impact of production compared to other types of wood.
When freshly sawn, the timber has a moisture content of sixty to eighty per cent which will start to diminish immediately afterwards as the timber naturally air dries. This process is known as seasoning and as the wood dries it becomes harder and resistant to any further uptake of moisture.
The seasoning process takes one year per inch of thickness of the timber, so for example five inch thick green oak beams can take up to five years to dry completely. The final moisture content will be as low as four to eleven per cent depending on the area of the country.
A natural side effect of this process is a certain amount of shrinkage as the wood loses mass from water loss. This should be taken into consideration when planning any project using green oak to guarantee the desired end product meets the original specifications.
Ignoring shrinkage can lead to a loss of stability and strength in the finished structure as joints can shrink apart. This will then lead to further work to remedy the issue. However, if taken into consideration this shrinkage can lead to exceptionally strong structures as the joints between parts shrink together, forming a stronger bond.
Green oak shrinkage can cause glass to break or doors or windows sticking so it should be avoided for door or window frames. As the wood dries its colour changes to a silvery aged appearance that many find attractive but if preferred the timber can be treated at the outset to retain its original colour.
As noted earlier, European oak is far more hard-wearing than other types of wood. Its naturally low water content and high water resistance once seasoned makes it far less prone to decay. Many European oak framed buildings still retain the original timber used in their construction hundreds of years ago.
This means that when building with green oak for any project, the timber will never need to be replaced in their lifetime. Due to the naturally high tannin content of oak it is also remarkably resistant to fungal growth or insect infestation.
Ease of Use
Compared to air or kiln dried oak, green oak is relatively soft and therefore easier to work with. Even with power tools, oak can be difficult for the domestic user to cut or shape. As a result, working with green oak not only makes the job easier but speeds up construction and reduces the need for specialised tools and equipment.
Concrete and plaster can require moulds, reinforcement and long drying times which are all avoided when using timber instead. As little or no maintenance is required, once the project is completed no further work is needed.
No consumer ever has a limitless budget for the project in hand and the lack of processing or treatment makes green oak an economical choice. Air or kiln dried oak can be three to five times as expensive due to the added production costs to the supplier and this saving is passed on to the consumer.
As green oak wood is freshly sawn it can be cut to the exact size the consumer requires, avoiding the need to purchase standardised planks and beams that are larger than needed. This also reduces waste as only the green oak boards or beams needed for the construction are purchased.
Timber as a whole has the lowest embodied carbon dioxide of any commercial building material, according to studies by the UK Timber Frame Association. Green oak, which is sourced from sustainable forestry projects, has been deemed carbon neutral, which is rare for any building material. As the oak trees grow they absorb carbon dioxide from the air and the oak itself traps carbon when used as a building material rather than releasing it into the environment.
Green oak cladding can reduce home energy costs by up to thirty three per cent due to the natural insulating properties it possesses. The side effect of this is a reduction in the carbon footprint of the building itself after construction along with the low carbon footprint of producing green oak itself.
Low Environmental Impact
Green oak has the lowest environmental impact of all building materials. European oak production is monitored by the FSC (Forest Stewardship Council) and PEFC (Programme for the Endorsement of Forest Certification) to ensure responsible and sustainable management of resources. This ensures forests are not overly depleted and replanting is responsibly maintained.
The lack of chemical treatment or industrial drying of green oak eliminates the production of environmentally harmful by products. The hard-wearing nature of the timber itself means chemical preservatives or pesticides are not necessary. Any excess wood left over from the cutting of the timber can be repurposed as bracing or pegs for construction and sawdust and offcuts can be sold as fuel or animal bedding.
Unlike man made building materials, wood needs no industrial or chemical processing to recycle waste and the maximum use is made of the material itself, minimising the need for recycling.
At Hardwoods Group we offer a variety of oak products, including green oak produced to your specifications. Why not look at our oak frame designs using the best quality timber to create a range of both contemporary and traditional oak framed buildings for you to choose from. View our range or contact us for further information.