Oak is a timber species revered in British culture.
Oak wood is associated with history, tradition, longevity, steadfastness, durability, toughness, and strength; across centuries we’ve anthropomorphised the ‘great Oak’ tree and it’s timber believing it represents us and that our lives are inextricably linked.
For us here at Cocking Sawmills this is only too true. Even today English Oak (Quercus robur) is our bread and butter. We know, from the last 3o odd years of sawmilling, that the same goes for many of you joiners, framers, foresters and furniture makers too.
It’s a timber species we all know so well that we don’t stop to question or ponder on it’s qualities, it’s properties, it’s potential and it’s limitations (does it really have any?!). We eat, sleep and dream in Oak and yet, more often than not, we take it for granted.
Well not today. Today we’re going back to wood school to talk about our beloved Oak, starting with names…
What’s in a name?
Meet Quercus. In Britain we have woodlands full of Quercus robur (pedunculate Oak) but it’s also native across Europe. We also come across Quercus petraea (sessile Oak). Both species are talked about as European Oak, but that includes French Oak, English Oak or Eastern European Oak. There are many (so many) variations in the Quercus gang it would be a waste of ether for us to list them when Wikipedia are doing such a good job but it’s worth remembering that although they all share a name they certainly don’t all share their timber properties.
NB We separate our origins so we can source specifically and from a single origin. In the British timbers we also document provenance, including woodland.
Oak trees are deciduous (at least our Quercus species are). They’re commonly found across the country and the rest of Europe from well managed, sustainable woodland sources. Oak timber has pale yellow brown heartwood with medium coarse grain, tending to be straight and uniform. Exceptions are when quarter sawn, brown/yellow streaked, or pippy/burry. Workable with machine or hand tools depending on grain pattern but very difficult to treat (moisture & acid content). Takes glue, stain and polish well. Strong durable timber with medium moisture movement.
The proper Technical Info from TRADA
Wood Type: Hardwood
Mechanical Strength: High
Treatability: Extremely difficult
Moisture movement: Medium
Texture: Medium to coarse
Density (Kg/m3 at 12% moisture): 720 but varies by up to 20% +/-
The Oak Timber
In timber form Oak is of course a hardwood. It is known for it’s golden yellowy brown colouring but this has variations depending on origin and grade. The sap and heartwood are contrasting colours. The sap’s easy to see but is also a nice creamy colour and can be incorporated into projects if appropriate. The annual growth is strongly marked and the quarter sawn boards show a glistening flame pattern through the grain called Medullary Ray. Oak grain actually has an enormous range although technically documented as medium coarse. It is possible to find tight, narrow, straight, fairly smooth grain but also broad coarse and wild grain. Origin, age, soil properties, weather conditions… all these things contribute to the visual and mechanical properties of Oak.
Oak trees can grow to substantial dimensions of 30m or more in height and up to 1.5m diameter. Naturally it follows that Oak logs are substantial in size too, which makes it ideal for structural timber as well as oak beams and mantelpieces.
Our British Oak is often short in bole (trunk). It is longer when grown in managed woodlands rather than open Estate land. Diameters however can be enormous as long lived estate Oaks survive in situ for centuries and produce great widths. By contrast, the deep European forests can produce incredible lengths and great straightness common with well managed forests. The straightness allows for maximum sawn width yields.
In the past we have been limited by timber handling equipment (kilns, cranes, lorries, even doorways) which determined the sizes of available timber but in recent years, as part of our aim to grow the market for homegrown timber, we have made the decision to seek out and facilitate the drying of long and wide boards in local timer but also when we buy and import logs and timber from Europe or North America.
Oak stock is represented in every product area. We produce fresh sawn oak beams and cladding every week. We saw logs into boules which become our waney edge board stock after drying and there is always large square edge stock to select from, sourced from France, from Croatia, from Serbia and from other places we can find excellent certified sources.
The stock grades cover all normal Oak grades. We keep large volumes of Character, Prime and Super Prime square edge. We always have English & French waney edge. We select for quarter sawn and we keep Pippy Oak in light, medium and heavy Pip as well as Burr when we can find it. We rely on Tom’s log buying expertise to surprise us with the rarer feature grades for furniture and cabinetmaking timber.
In terms of available thicknesses, Stock Kiln dried boards range 18,2o, 27, 34, 41, 54, 65, 80, 100, 120mm thick with squares stocked up to 150mm. Typical board widths go from as small as 150mm on a crown board up to 1.0m or more sometimes for a centre board. The majority are 300-500mm and, as you can imagine, the wide boards sell very quickly. Homegrown Oak lengths can actually start quite short at around 2.0m but go up to 8m or more. Longer is harder to come by, but we’re working on it !
Download our OAK pdf which gives a good overview of the Oak we stock
When you look at Oak, it’s durability, it’s strength, it’s aesthetic qualities, it’s technical qualities, it’s extensive and ready availability in a wide range of products, not to mention the inherent knowledge base around Oak it won’t surprise you to know Oak can be used for almost anything.
Popular among green Oak framers & builders, joiners, furniture makers, carvers, turners, garden designers & groundworkers and anyone else that uses wood for anything at all. Oak can be applied to almost any interior or exterior purpose and is the strongest, most naturally durable timber option in homegrown timber due to Tannin content and density. Fresh sawn, it’s yellow brown colouring can take an exterior finishes once surface dry, otherwise it will silver down very respectfully.
It’s about the most popular and widely used timber in Europe. Use it round, use it green, use it riven, use it sawn, planed, profiled, air dried, kilned, oak boards, oak beams, English, French, Croatian, German, quartersawn, crowncut, pippy, burry, with bark or de-barked, use it through and through or square edge, super prime, prime, character rustic or downright downgrade. Oak is a great non-toxic option for use in children’s playgrounds and school landscaping and needs no additional chemical preservatives.
How are you going to use your Oak?
Alternative & Mixer Species
For alternatives to European Oak swap continents to America and you find Quercus rubra (red Oak) Quercus alba (white Oak) both usable and available for furniture and joinery. We don’t keep a lot of North American stock but we offer the option for joinery and furniture customer preferences. Other alternatives for hard tough internal timber could be Beech or Sweet Chestnut. For structural purposes Sweet Chestnut or Douglas Fir could work.
In truth there’s endless fun with combining species but for good visual mixers we like Ash for nice grain patterns and gentle, cool contrast colouring and we like Walnut as a deep, warm contrast colouring.
Oak & Tannin
Tannic acid, also known as Quercittanic acid, is part of the chemical make up of Oak. Tannin contributes to the inherent durability of Oak and is present all forms of the timber. The reason it should be noted is that although it is fixed within dry, aged wood, in oak with high moisture content or in oak that’s exposed to external weathering the tannin can leach and stain.
Fresh sawn timber, boards that are still high in moisture, external cladding and structural timber for framing may show tannin leaching. It can leave a brown stain (like a tea stain funnily enough!) on the wood surface, on the ground if it’s been standing or underneath if water has run and dripped over it in situ.
If you’re using Oak externally ask us about tannin in your project + see the link below for a blog about tannin.
OAK WOOD GRADES
For simplicity’s sake we talk about most of our stock in terms of Character, Prime or Super Prime to reflect our customer’s general project requirements.
The specific scientific timber grades have been documented to make visual identification of grades universal. One great reference for this is the publication Making the Grade, well worth a read if you want to build your wood knowledge and understanding.
Technically, as documented by Making the Grade, this refers to a relatively low grade of timber that exhibits a mix of inter-grown knots, pin knots, heart shake, or colour variations.
At English Woodlands Timber we use the term Character Oak to describe a very broad grade that includes anything that falls below Prime, 1st grade Oak standards with exceptions only for our feature grades
This then means under the term Character our boards include 2nd Grade Oak and incorporated sub grades plus may include pin knots, splits, cracks, heart shake, insect attack, bark pockets, areas of rot, sapwood and colour variation.
As an overview we don’t put restrictions on boards in this grade providing the appearance and mechanical properties of the particular timber are suitable for its intended purpose.
Our actual stock then incorporates particular selections within the grade of Character Oak.
Waney Edge Character Oak stock will generally sit in original boules and we select and measure from the stack depending on each customers requirements, preferences and the particular use for the board.
Square Edge Character Oak stock is a different thing altogether. Here a more sophisticated, applied grade selection has been carried out and boards are stocked in packs of similar grade qualities.
These packs tend to contain the higher qualities of Character Oak wood, the 2nd grades which exclude more rustic features and in terms of appearance are more representative of real Oak with good grain patterns, sound knots, lovely honey colouring… everything one normally expects from real Oak.
This means by selecting from packs it’s possible to get a consistent grade and overall ‘look’. This speeds up selection and is useful for flooring projects, cladding projects, bespoke kitchens, door manufacture, furniture range manufacture etc where all boards need to have similar colouring, knot sizing and grain pattern. By selecting from graded packs of Square Edge Oak you get a reassuring consistency, even in Character grades.
The term Prime has always been used to indicate the top grade of timber.
It’s criteria is used to verify the mechanical properties of a board by visual means and seeks to differentiate Prime graded boards as boards that are fit for specific purpose, namely joinery, cladding, cabinetry, furniture making or highly machined timber products.
In Prime Oak we allow one inter-grown knot* up to 20mm diameter or several small knots up to a 20mm combined diameter**. One small bark pocket is allowed. Small sap bands are allowed – we follow the French convention of ‘one in, one out’, the underlying principle being to provide a ‘fair measure’.
In selecting from Prime Waney Edge Oak boards to a cutting list or customer requirement we would measure out the waney edges (re:sap), the heart cracks, large knots, shakes and other typical board features that are not allowed within the grade so the board measure (the bit you pay for) would only include what comes within Prime grade, although you may receive a whole waney edge board.
Prime Oak wood colouring is relatively even but for particular consistency of colour the best method of selection is to choose boards absolutely from the same origin, and ideally from the same boule.
In this way Prime timber does waste more wood than other grades but it is how a single, unique waney edge board can be used to select for a multitude of grades and purposes and is one reason we love our waney edge timber.
Our Square Edge Prime Oak timber has been pre-selected into grades at the milling stage and is an easy, reliable, fast way to buy Prime Oak, especially if you are self-selecting. These boards can be just taken straight from a timber stack and each board measure meets the stated grade on at least one face, if not both.
For homegrown waney edge Oak take a look at Making the Grade – Oak grade 1 for illustrations of Prime Oak
SUPER PRIME OAK
Super Prime is a term that indicates a grade ‘above’ Prime.
It’s a grade that has been normalised as a timber grade in the UK for high grade imported square edge Oak. It’s a description we use of a grade that goes above and beyond normal Prime Oak timber qualities and requirements.
Super Prime is a selection of the most pristine, the most clear, the most pale and evenly honey coloured, usually Eastern European, Prime Oak wood you will ever see. In most mills it’s edged after kilning in a re-grading process. More labour intensive but definitely serves to refine the grade. I think we’ve called it ‘relentlessly clean’ before and that about sums it up.
Knots aren’t strictly excluded but if you see one it’ll be a small pin knot and only visible on one face. The other face will undoubtedly be clear. The same applies to sap. In Super Prime Oak there will not be a lot of grain pattern. There will not be a lot of variation of anything. There will be no dark colouring. No bark pockets. No wild grain. No splits, no cracks, no shakes. There may be a high proportion of Quarter Sawn boards. There may be a lot of very flat boards. There may be a lot of very straight boards.
If you have a large run of Oak doors and you need them all to look and behave the same, use Super Prime. If you need a quiet, understated solid wood for an interior surface use Super Prime. If you need simple elegance with embodied strength and durability for a feature staircase use Super Prime.
Although it’s a little hard for us to admit, Super Prime Oak has superior qualities that cannot be replicated by other grades or timber species. For this we are grateful as it is a pleasure to work with, a pleasure to select from and a thrill to see it in situ in a customer project.
FEATURE GRADES IN OAK WOOD
This is a very popular feature in Oak resulting from the presence of frequent small pin knots. The can appear singly, in 2’s or 3’s (cats paw) or in groups of growing density which we describe as light, medium or heavy pip depending on number of knots in a group.
TIGER or BROWN OAK
This describes an attractive colouration caused by the beef steak fungus Fistulina hepatica. We see it in Oak and it produces two different effects.
The first is a narrow brown streak going down through the grain that can hit and miss to produce a variable stripe. This is the Tiger Oak, surprise surprise! Super jazzy, it’s a wonderful vibrant alternative to an exotic species therefore prized by sustainable minded, conscientious designers and makers.
The Brown Oak is where the whole whole cross section of the heartwood is affected, leaving a solid brown colouring known, funnily enough as Brown oak. This may not sound too special but the colouring is so deep and chocolatey and different to anything else that it’s a joy to see and an absolute gift to cabinetmaker looking for that something special.
Burr describes what appears to be dense area of pin knots covering more than 50% of a board. It’s a spectacular visual effect, much sought after and is actually a feature caused by irregular grain growth around groups of epicormic buds.
Although Burring does change the mechanical properties of a board by interfering in the growth of the grain as the knots are so tiny and woven into the grain the board stays intact. Burr boards take more care to dry. They retain moisture differently to a straight grain board. They dry differentially in thickness and hold onto moisture in little pockets. This can produce undulations in the sawn surface but they can be worked very successfully for furniture making, box making, cabinetry etc
We have normal Burr oak wood boards but we also keep the actual burrs (big lumpy things) taken from the outer log prior to sawing. These are for special projects, wood turning, one off furniture pieces and the like. If you’re a Burr fan you’ll love these pieces.
QUARTER SAWN OAK
This is the term for boards sawn on the radial plane to reveal the very decorative figuring known as medullary ray. A visible medullary ray (shiny flame pattern) and vertical growth rings in the end grain indicate quarter sawn timber.
This vertical grain means that boards will have maximum potential for stability. This is due to an absence or relative absence of curve/growth ring in the thickness therefore the absence of tension and/or compression inherent in the growth rings that act on boards to cause cupping.
We select particular logs to saw by the traditional quarter sawn method and of course our T&T*** sawmilling produces a number of quarter sawn boards near the centre of every boule. Sawing both methods allows us to select for the super wide quarter sawn boards that occur in boules whilst maintaining the ability to select for varying strengths of the fabulous grain pattern that occurs in outer and crown boards.
The best of both worlds!
*inter-grown knot, alternatively know as sound knot = a knot that the grain has grown through/into rather than around/against so that it is integral in the body of the timber. An unsound knot has grown separately to the flow of grain and can move separately, can be dislodged or even fall out.
**E.g. 1 knot at 6mm diameter + 1 knot at 5mm diameter + 1 knot at 7 mm diameter = a total 18mm diameter and therefore is allowed within Prime grade
***T&T Through & through sawing produces the same boards as plain sawn or also rift sawn
There are several species of Oak tree throughout the World, but the Oak grown in England and Western Europe is Quercus Robar, known as common oak, pedunculate oak, European oak or English oak.
The provenance of Oak wood can have an effect on its properties, with various factors changing the qualities of the wood. These can range both from country to country and region to region, with soil composition, light levels and weather affecting the cut wood.
Oak is the most common woodland tree in England. It has been used as a construction material in Britain for many centuries, and has been important enough to have assumed the status of a national emblem. English Oak was one of the drivers of Britain’s success as a colonial power, with oak being used as the building material for the Royal Navy and its dominance of the seas. English Oak is characterised as one of the strongest oaks, with more interlocking grain than other European oaks, creating a fine, hard surface. It can be difficult to work, but often also has a great deal of character. The term “English Oak” can refer to oak grown in England or the species Quercus robur, so be careful of the meaning when people refer to “English Oak”. They could mean Quercus robur that is not necessarily grown in England.
France has a similar historic affinity with the oak tree. Some Oak trees were revered as sacred by the Gauls, and Druids would cut mistletoe growing on them for fertility rituals. Oaks have also been used in construction and ship-building for centuries. French Oak is known for its high levels of tannins, meaning it absorbs colour stains evenly and retains stain for longer.
Eastern European Oak
The forest of central and Eastern Europe are also a great source for Oak timber, with a lot of our current stock being imported from Croatia. The pedunculate oak of the Croatian region of Slavonia is considered a separate subspecies (Slavonian oak). It is a regional symbol of Slavonia and a national symbol of Croatia.