Timber grading and specifically oak grading can be carried out in two ways, visual and machine testing. Historically, visual testing was the main system used due to the lack of suitable machinery and the prohibitive cost. This is still the main type of grading used by many timber merchants. Suitably qualified and experienced staff can use visual cues alone to assess the properties of the timber. Originally, machine testing was mainly used to test strength through weight tolerance and resistance to bending. However, modern machines use X – ray scanning, moisture measurement, digital imaging and a wealth of other methods to grade timber.
For a joiner, builder or architect designing or working with timber the ability to ensure they have the right material for the job in hand is paramount. Thankfully, reputable timber merchants will grade the materials they supply and provide ratings for their product to assist the consumer. European Standard grading gives a clear, concise rating that can be understood at a glance once the reader has had timber grades explained. This is based on three factors – wood type, product and quality, to give an accurate assessment of timber strength and the aesthetic properties of the material.
European Standard Classification
Here we see the timber grades explained simply using the European Standard. This system uses a three character format to represent the three main factors used to grade timber, for example Q–BA or Q–B1.
The Three Main Factors Used to Grade Timber
There are two species of European oak that are used in construction, Quercus Petraea and Quercus Robur. As its genus is Quercus, all oak grades will be represented by a Q in this category. This explains the first character of the European Standard Classification that we see above.
This is divided into four categories defined by the source, size and purpose of the timber. These are represented by the initials B, S, F or P, depending on the category. This is the second character.
B – Boules
Boules are boards cut lengthwise from the tree and include the bark and sub – bark sapwood. This is also known as Waney Edge oak. All boules must be cut from the same tree and are described as unedged boards. These can be any thickness but must measure at least two metres in length. The width of the board at its narrowest point, as well as physical quality, will determine its quality grading. The entire boule is assessed for quality and at least 65% of the entire boule must be of the quality needed for the grade given.
S – Selected Boards
Selected boards are identical to boules in appearance and are also unedged. However, there is no need for them to all be cut from the same tree. The visual appearance must be consistent between boards. Grading due to width follows the same criteria as for boules. As with boules, these can be cut to any length or thickness required for the customers’ requirements. Each board is assessed for quality and no more than 10% of the boards present can be below the quality rating for the batch as a whole.
F – Square edged
This is the designation given to kiln dried strips or boards with sawn edges that have been cut to size. These lack the bark common to the previous categories and have regular straight edges, hence the name. Square edged timber quality is mainly based on the appearance and consistency of grain, along with the presence of knots or other features.
P – Beams
These are usually freshly sawn green oak and due to the nature of their use are thicker than other timber. They can be cut to any length required and quality is judged on the distribution of features along their whole length.
The third and final character of the grading describes the quality of the timber. ‘A’ grade represents prime quality and the numbers 1-3 describe lower levels of quality in descending order. Grade 4 exists but is best avoided due to the relatively poor quality of the timber. The quality of the timber is judged on the presence of what are known as features. These are imperfections or flaws in the appearance of the wood. However, these can be desirable for character pieces for the novel appearance they give the finished piece.
As the name and the ‘A’ designation suggests, this is the highest grade of oak. It is as near to perfect as possible for a natural material. Very few knots will be present and one bark pocket and some small sap bands are permitted. Prime oak is the best choice for furniture, cladding or joinery where a particularly flawless finish is desired.
First and Seconds
Also known as FAS grade, first and seconds is equivalent to grade 1 in quality and is very similar to prime grade. Again, there will be very few features or imperfections to timber of this grade. It does provide a more cost-effective alternative to prime, with only a slightly diminished appearance.
Joinery grade timber is the equivalent of quality grade 2, also known as secondary grade timber. More knots, sap and other features are allowed for this grade than prime or FAS. This is more often used as structural oak or for jobs where a finer finish is less of a priority.
Character is grade 3, but this does not mean it is a poor product. In fact, the presence of features such as colour variations, splits or knots sometimes makes it more desirable. The irregular appearance lends itself well to projects with a rustic feel and can be quite eye catching. As a result, this is the first choice for many feature pieces.
Pippy oak is characterised by clusters of small knots. It is also known as ‘patte de chat’ or ‘cat’s paw’ due to the similarity of the pattern to tiny paw prints. It is ungraded but can be used to give an unusual and interesting finish to feature pieces.
At Hardwoods Group, we pride ourselves on the quality of our products and we only supply timber of grade 3 and above. View quick explanations and images of our oak grading.