Wood Knowledge: what is green Oak used for?

Mar 14, 2024 | wood knowledge

Historically, green Oak has played a significant role in British construction and woodworking. Some of our customers have asked: what’s the difference between green Oak and seasoned timber?

In this article, we’ll provide a helpful overview of this most versatile of timbers, answering questions such as: what is green Oak used for and why?…

First up: what is green Oak?

Quite simply, green Oak is oak that has been freshly cut and not seasoned. Green Oak has a higher moisture content than seasoned Oak as, by its nature, seasoning allows the moisture to naturally evaporate and reduce over time.

Also known as ‘fresh sawn’ or ‘unseasoned’, the use of green Oak for framing, cladding – even wattle and lath in traditional building – dates back many centuries. Green Oak was used to build barns, houses, covered markets, communal buildings, decks, quays and even gallows. It’s testament to the timber that it is still commonly used today.

There are several advantages to using green Oak in construction and woodworking projects.

The benefits of green Oak

Green Oak offers many benefits over other natural and manmade construction materials, including:

  • Strength
    The natural mechanical strength of Oak enables it to bear heavy loads. It is ideal for structural components like beams, trusses, posts and frames
  • Workable
    Green Oak is comparatively easy to work, even with hand tools, due to its soft structure. By contrast, seasoned Oak – having had time to dry, harden and change structure – is much tougher, especially on hand tools
  • Environmental benefits of a renewable material
    Green Oak has a low carbon footprint compared to many building materials, especially if it’s sourced with low transportation miles. It is considered a sustainable building material because it is a renewable resource in that Oak trees naturally regenerate or are planted, then can be harvested from responsibly managed forests
  • Durability
    The longevity of green Oak (centuries!) reduces the need for replacements, which further reduces its environmental impact
  • Affordable and available
    Although green Oak is lower in cost than seasoned Oak, both offer affordable readily available constructional timber options.The slightly higher cost of seasoned Oak beams is because – as a dense hardwood – large sections of Oak dry painfully slowly! A substantial thickness required for structural components can take years of air-drying to lose excess moisture. Part of the raised cost of seasoned Oak can be because it requires more processing time, as we store, stack, turn and air dry it in our woodyard, gaining in age and value for certain kinds of timber framing use
  • Satisfaction in craftsmanship
    Working with any structural Oak requires knowledge of traditional carpentry joints and skill with hand tools like chisels and pegging methods or machine tools like chain morticers
  • Major aesthetic appeal
    We’ve said it before, but Oak is lovely stuff and full of character. Green Oak can (should!) contain natural grain patterns, some knots and a coloration ranging from pale yellow to rich golden brown when newly worked. When, and if, weathered, the colouring silvers, greys and even deepens to an almost black on north facing facades

With versatility, strength and undeniable good looks, green Oak is a sought-after material for both residential and commercial projects, from timber framing to roof structures, using traditional carpentry and joinery methods.

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The challenges of using green Oak

All fresh sawn timber – and that includes green Oak – shrinks and moves as it loses moisture. This ‘moisture movement’ leads to inevitable changes in the section dimensions so must be considered during the design and construction stages.

Careful specification, correct Oak grades, skillful design and good timber detailing techniques – accounting for shrinkage and movement – can be deployed to mitigate these issues and ensure structural integrity and successful, healthy buildings.

With exposure to ultraviolet, unfinished Oak will bleach and silver over time. While green Oak is naturally resistant to decay and insect damage, it can be boosted by appropriate surface treatment to maintain its appearance.

What is green Oak used for today?

Structural green Oak beams and other components are commonly used for:

  • Timber framing
    Green Oak is often used for the structural framework of buildings, beams, posts, trusses, bracing et al. Not only does its strength allow for large spans and heavy loads, timber framing with green Oak also creates a striking and long-lasting structure. It is ideal for eco-friendly buildings.
  • Carpentry
    Carpentry components for traditional building, such as lintels, thresholds, window reveals and sarking.
  • Exterior cladding
    Green Oak boards are ideal for exterior cladding and siding. The timber hardens and weathers in situ to develop a weathertight fit and a pleasing silvery natural patina.
  • Decorative interior finishes
    Green Oak can be used for interior features such as mantelpieces to add natural texture, warmth and character.
  • Furniture-making
    There is a school of furniture making crafts-people who use green Oak to build chairs, benches, banquettes and tables. They employ the natural shrinkage in jointing methods, building in strength and durability which has a unique aesthetic appeal. The easily worked green wood can be shaped and carved into intricate designs.
  • Landscaping and outdoor structures
    Green Oak is used for landscaping projects, including fences, garages, summerhouses, pergolas, gazebos and other structures. Its durability, weathering and resilience to outdoor conditions make it an ideal choice for such applications

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Our custom-cut structural Oak

When it comes to our structural Oak beams and cladding, we categorise it in the following way:

  • FRESH SAWN (FS) is anything up to 6 months from the sawn date
  • PART SEASONED (PS) is 7-24 months from the sawn date
  • SEMI SEASONED (SS) is from 25 months from the sawn date

The age of the sawn structural section corresponds to a level of drying/seasoning.
For engineering calculations, our structural timber is technically ‘wet graded’ as, due to section size, it cannot reach the moisture content required for ‘dry graded’ structural timber.

In a hurry? We have a constant stock of green Oak and seasoned Oak structural beams – measured and tagged in a variety of standard (ish) sizes.

Alternatively, custom orders can be cut-to-size to your exact dimensions, whether you need beams, posts, curves, crucks or bracing. As well as fresh sawn Oak/timber beams we offer green Chestnut and Douglas Fir. Simply give us a list of components – Qty x Th x W x L – and we’ll cut to your spec for collection from our yard or delivery to your site.

Choose sustainable fresh sawn timber

With a rich history and the Government’s active encouragement of replanting native hardwoods, green Oak will continue to play a vital role in British construction and woodworking for the foreseeable future.

If green Oak is suitable for your project, please support sustainable practices in the timber industry and engage with a reputable and certified supplier. As certified timber suppliers, our fresh-sawn structural Oak sections and cladding are milled in France at our partner mills (we also source seasoned structural stock in France) and travel between 200 and 215 miles to get to our woodyard (depending on roadworks!) an average 9 miles per cubic metre of green Oak.

MORE

Select and buy from our range of fresh-sawn structural timber

Read more about Oak

Read TRADA’s ‘Principles of green Oak construction’ for best practice techniques for successful green Oak building specifiers

Slave to the detail? Get hold of TRADA’s ‘Green Oak in Construction [1]’