Oak Cladding


Characteristics and Grain Features.

Annual/Growth Rings: Concentric ring of wood added every year to the growing tree.

Burr, Cats Paws or Pips: Abnormal growth caused by a mass of small twigs that become trapped in the grain as the tree grows.

Burl: Similar to a burr, but formed by injury to the tree, akin to scar tissue in humans.

Cambium: A layer of cell that increases the girth of stems and roots.

Characteristics: Attributes of a tree used for identification; colour, grain, hardness, lustre, odour, resin content, structure, taste, texture, weight, etc.

Crutch/Curl: The figure in the grain, produced by the junction of a break with the stem or between two or more branches.

Figure: The ‘ornamental’ markings or design in the tree. The figure of a tree can be artificially produced or natural.

End Grain: The grain apparent on a cross cut surface section of a log. Cut at a right angle to the length of the log, it is by far the strongest and most durable part.

Heartwood/Duramen: The inner part of the exogenous tree that does not contain living cells. In contrast to ‘Sapwood’ it is usually harder and heavier and more durable.

Knots: A section through a branch embedded in the trunk of a tree due to natural growth.

Medullary rays: Radial vertical sheets, or ribbons of tissue formed across the growth rings of trees.

Ripple/Fiddleback Figure: Figure in the wood caused by the buckling of fibres due to compression.

Sapwood: The soft wood, just beneath the bark in tree trunks.

Spalting: A fungal attack, which occurs when a tree is left in the round for an extended period, visible by fine black or brown lines that do not run necessarily with the grain.

Wane/Waney Edge: The presence of bark and/or sapwood on one or more edges of the board.


Brown: Brown colour is found in a number of species, caused by either; Beef Steak Fungus or rot penetration from the tree root.

Harewood: Sycamore or Hard Maple dyed for cabinet work. The wood is chemically treated with ferrous sulphate or other salts, which react with the natural chemicals in the wood to produce a silver grey hue; this will slowly fade with age.

Liming: This is applied to Oak when an attractive limed effect is obtained by rubbing a paste of chloride of lime and water into the grain.

Olive: A beautiful feature found in Native Ash. It is attractive variegated brown heartwood with differing shades of light and dark grain.

Marbled: An attractive feature found mainly in Sycamore but can occur in other light coloured timbers. It appears in many forms and colours as light and dark variegated streaks.

Mineral Streak: This can occur in any hardwood and is caused by the type of soil in which the tree is grown. It is not a defect, but complicates uniformity.

Steaming: A process with a number of applications in the use of timber; making it soft for bending and veneering; to sterilise timber against fungi or insects; or in kiln seasoning to prevent case hardening and unequal seasoning or reducing contrast between sapwood and hardwood.

Silvering: A process used to achieve the silver weathered seasoning effect apparent in Oak which would normally take a number of years exposed to the elements to occur naturally. .

Tiger Steaks/Stripes: These occur in a number of species, but mainly Oak and Sweet Chestnut in the form of dark brown stripes running along the grain. The effect is caused by the initial stages of Beef Steak fungal attack or rot penetration from the root, yet gives an attractive contrast in the grain.

Weathering: Occurs when timber is exposed to the elements, i.e. rain, sun and wind.

Whiteness: A quality of freshly felled, lightly-coloured timber, that is important to retain.


Dead Knot: A knot that is dead and cannot be included in the finished product, usually cut or measured out.

End Shake: Occurs at either end of the board. It is a straight split that individually can be left in with good cutting, but multiple splits render that part of the board unusable and necessitate cross-cutting or measuring out.

Face Shake: Normally occurs in crown or plain sawn boards in the form of fine shakes running with the grain. The shakes can be easily filled and do not class as a major defect.

Heart Shake: When the heart of the tree breaks out on the surface of the board.

Metal Staining: A number of timbers react with ferrous metal and produce a dark blue stain.

Rot: The decomposition of wood due to fungal attack. Rot is usually cut out, however sometimes it cannot be seen until the board is worked.

Sticker Shadow: Occurs during the drying process from the sticks used to separate the boards.

Warping: Sometimes referred to the casting or twisting of a plane flat surface.

Worm Attack: It is very rare to find a live worm in the heartwood of seasoned timber. However, live wood wasps can be found in the sap wood of well air-dried Oak. Ambrosia beetles can be found in logs left on the ground – however, if the beetle is dead it proposes no problem to the finished quality of the product.

General Trade Terms

Backing Boards: Machined tongue and groove boards used for the backs of dressers and furniture.

Beams: Large sections of timber, which are held in stock, fresh sawn and or air drying in standard sizes.

Billets: Large section boards, three inches and thicker, held in stock air drying prior to being resawn into beams and purlins

Boxed Heart: A method used for converting a log in order that the centre or heart is wholly contained in one piece or square enabling greater stability and even drying.

Circular Saw: A type of saw used in order to achieve a fine clean saw cut.

Cutting List: A detailed list of the specification of each piece of timber required.

Drawer/Drawer side stock: Timber produced specifically for drawer production where short and narrow timber may be suitable.

Finished Sizes: The finished length, width and thickness required once the timber has been machined and worked.

Nominal Sizes: The rough sawn size of a board before it is worked.

P.A.R. Planed all round

Planed: Indicates that a board has been worked to its required finished thickness.

P.S.E Planed squared edged

Specific Gravity: The relative weight of any substance compared with that of an equal volume of water. Varies greatly in each tree species.

Weight: The weight per cubic foot of a substance is Specific Gravity x 62.5lbs.

Lbs/ft3: The weight of the timber at an average moisture content of 12%.

Guide to Timber Weight Conversion:
55lbs/25kg = 1ft3 Commercial
66lbs/30kg = 1ft3 Exotic
79lbs/36kg = 1ft3 Ebony
The above are a guide only and are approximate.


Air Drying: The process of seasoning the timber in the open air – protecting it from the sun and rain by cover boards or an open sided shed. Air seasoning is required for most species prior to kiln drying.

Case Hardening/Honeycombing: Warping as a result of stress, after seasoning, between adjacent layers in the structure of the timber. Caused by too rapid surface drying in the kiln.

End Racking/Plastic Stickers: Some timbers, such as Sycamore are prone to sticker marks, which occur when the moisture in the board cannot be released from a freshly sawn board because it is trapped under a wooden drying sticker. End racking prevents this by placing the boards vertically for a period of time on the sticker. Modern plastic tickers now have a shape that avoids the problem altogether.

Equilibrium Moisture Content: The moisture content at which wood is stable and in equilibrium with the humidity of its surroundings.

Equalising: The process at the end of a kiln drying run by which the moisture content of the whole kiln change is equalised before cooling down and discharged from the kiln chamber.

Green/Wet: The term for freshly sawn timber.

Kiln Drying: The process of drying timber to a moisture content which cannot be achieved by a natural air-drying process. It is carried out in chambers where the temperature and humidity are mechanically and scientifically controlled.

Kiln Shrinkage: When any timber dries, some shrinkage will occur with the normal loss in volume being around 6% to 8%. In order to allow for this, when sawing a log we saw the thickness of the boards ‘off the saw’, which allows a minimum of 6% over the required thickness after kiln drying.

Moisture Content: The percentage of moisture present in wood.

Part Seasoned: The term used for Beams and Billets, which have been air drying for a period of 6 months or more. During the first 6 to 12 months of air seasoning, beams will settle down and if movement and face shake are to occur it will be during this initial period of air drying.