Grade and Colour Variation in Wood Flooring: What you need to know

Knots are unique circular or oval-shaped imperfections in the wood grain, with a darker coloured centre, occurring naturally in trees where the base of a branch grows out of the main trunk. These markings vary in size and can extend deep into the core of the tree. There are two types of knots:

1. Dead knots - where the core has fallen out or been removed and is filled with a coloured wood ‘filler’.
2. Live knots - where the core is intact and does not require filling.

Knots give a unique, natural character to wood and are more commonly seen in light feature, feature and rustic grades.

Sapwood is a distinct, lighter-coloured streak in the outermost portion of a tree trunk that acts as a ‘pipeline’ through which water passes from the roots to the leaves, making it a natural occurrence rather than a defect. Sapwood is the younger wood of the tree that grows around the older, darker centre of the tree (the heartwood) and darkens as the tree grows. Sapwood in wood becomes more prominent over time when exposed to sunlight/UV.

Staining the planks can help blend the natural characteristics and may lessen the appearance of sapwood. However, it will not eliminate them. Roasted or fumed wood has distinctive sapwood as the heating process causes an even greater colour contrast, making the sapwood even more prominent, especially over time.

These are ‘tiger-stripe’ looking distinct rays, waves or flecks against the grain extending radially from the tree’s centre outwards. They have a pale-coloured, natural appearance in wood and indicate that your timber has been crafted from quality quarter-sawn Oak. Medullary Rays can appear to have a shine to them, gleaming under direct sunlight.

Before a tree is sawn, it has a network of vein-like cells inside the trunk that transport nutrients from the heart of the tree to the extremities. When the tree is milled, specific cuts (usually those made to the top and bottom of the log) run across the tree’s vein-like cell structure at an angle, resulting in these unique vein-like markings known as medullary rays.

Cracks (also called shakes) are a natural-occurring split across the grain of the wood. There are many causes for cracks, such as uneven wood drying, high winds, frost, or felling trees past maturity.

These cracks are usually filled with a coloured wood ‘filler’, but in some cases, particularly with a Rustic Grade wood, they may be part-filled to add to the character or feature of the wood. The number and size of the shakes in your timber are again, affected by the grade you choose. 

Pinholes are a series of tiny black holes caused by an Oak pinhole borer and are found in wood in any grade below clear grade. The borer lays its eggs, and the larvae bore deep into the heartwood of stressed Oak. Borer cannot survive once the wood has been dried out and are gone before the wood is crafted into planks. 

Figuring (or cats paw) refers to the markings found on longitudinal surfaces of wood. The figure of a piece of wood can be linked to factors such as its grain and the way it was cut, or it may be due to the unique properties of the timber.
Figuring can also occur due to a burr (or burl) where a tree growth has grown deformed, extending far into the trunk, and has affected the grain.

Wood may contain ‘knots’ or ‘cracks’ which are typically filled with a coloured wood filler during the manufacturing process. The filler colour is carefully chosen to complement rather than precisely match the wood, and it may change from batch to batch. Please refer to the specification sheet of your selected product to understand which wood filler will be used.

For more information on what to expect when choosing engineered timber flooring for your project, read our Buyers Awareness article.