Oak Flooring Grades: What Knots, Sapwood and Character Actually Mean
Grading is the most misunderstood part of specifying a timber floor, because the language sounds like a quality scale and is not one. A higher grade is not a better board. It is a cleaner board. The structural performance is the same.
Understanding that distinction is worth real money, and it changes how a floor looks in a way no photograph will show you.
The simple version: ABCD
Most flooring conversations in New Zealand use a four-letter shorthand.
- A: clean, minimal variation, no knots
- B: slight natural markings and small blemishes
- C: visible knots and more pronounced grain
- D: larger knots and strong natural features
We supply a blend across ABC and ABCD rather than isolating a single grade. That produces a floor that reads as layered and authentic, because it reflects how oak actually grows. Trees respond to wind, soil, seasons and time. A perfectly clean board is not the norm. It is the exception, and treating it as the standard is what makes it expensive.
Why a clean grade costs four times as much
Selecting only A grade means discarding everything that does not meet it. In practice that can be three quarters of the raw timber from a log.
Two things follow. The price of a fully clean, knot-free floor can run up to four times that of a blended grade, entirely because of the waste required to achieve it. And the waste itself is the problem, because it means more trees felled for the same finished area.
This is the point where aesthetics and sustainability turn out to be the same conversation. A blended grade is the most efficient use of the log, and it is also the floor most architects prefer. Our wider sourcing position is set out under Sustainability.
Why character works in a contemporary interior
There is a reason natural materials are consistently specified into highly resolved spaces.
Character grounds a room. In a modern house with clean lines and hard surfaces, organic variation provides balance and warms the palette. Without it, an interior can read as clinical.
Character creates movement. A completely uniform floor is flat. Subtle variation lets the eye travel across a space, which is what makes a large open plan feel considered rather than empty.
Character carries information. Every knot was a branch. Every tonal shift records a growing condition. That is not sentiment, it is the reason the material cannot be convincingly printed.
The same thinking runs through the comparison with printed lookalikes, where the giveaway is a repeating pattern every few planks.
The formal system, for anyone specifying
Behind the ABCD shorthand sits a European standard. Appearance grading follows EN 975-1, and structural grading follows NF B 52-001 for load-bearing applications. The two run in parallel: one addresses how the timber looks, the other addresses what it can carry.
Grading codes are compact. Q denotes Quercus, oak. A product letter follows: B for boules, S for selected boards, F for strips and square-edged timber, P for beams. Then a quality indicator, A for exceptional, then 1 to 4 in descending order.
So Q-B A is a top-tier boules grade. Q-F 2X is square-edged timber at third-tier quality with sound sapwood on one face.
The suffixes are worth knowing. X means sound sapwood on one face. XX means both faces. Sapwood affects appearance and, in some applications, durability detailing, so it is called out explicitly rather than left to be discovered on site.
For beams, appearance grades map to strength classes under EN 338: Q-P A to D30, Q-P 1 to D24, Q-P 2 to D18. That correlation is what allows appearance-graded oak to be assigned engineering values for stair components and structural elements.
What each appearance grade permits
Reading down the scale for boules and selected boards:
- Q-B A / Q-S A: near flawless. Straight grain, knots under 20mm, sapwood rare, bark pockets and rot excluded.
- Q-B 1 / Q-S 1: very clean. Small knots under 5mm with limited larger ones, occasional isolated sapwood.
- Q-B 2 / Q-S 2: moderately clean. Slightly larger knots, one isolated flaw permitted, some sapwood or brown pith tolerated.
- Q-B 3 / Q-S 3: characterful. Knots to 70mm, sapwood and ring shake permitted. A gentle rustic result.
- Q-B 4 / Q-S 4: fully natural, with no restrictions beyond anything excluded by contract.
How to specify it properly
Grade is the one variable that cannot be judged from a swatch, because a 100mm square cannot show you the frequency of knots across a room. Two things solve it.
Order samples so you can see the finish and tone in the actual light of the room, then look at a laid floor at the Christchurch, Auckland or Queenstown studio, where the distribution of character across an area is visible. Completed work is also documented under Projects.
Grading and tolerances for each format are published in the Technical Specifications. If you are writing a specification and want the grade language checked before it goes out, book a design consultation.
