The woodworking world and timber industry have an entire codex of vocabulary and technical terms that aren’t always self-explanatory. This glossary aims to help you understand the timber terms in common use.

1st First Quality
1/2 Is a mix of first and second-quality timber. This can contain sapwood, sound knots, cross grain, or natural discolouration/streaking.
1/S/E One square edge, one waney edge
1+2 white  This term is used for the general description of Maple: white on one side, with slight discolouration on the reverse.
5-Axis CNC A machine to router, drill, saw, machine in the X, Y, Z, A and B tool rotation. A C Axis would be used for lathe work.
A/D Air drying from fresh sawn to below FSP
Air Checks Surface cracks small and along the grain – surface in tension
Architrave A main beam resting across the tops of columns
AD  Air-dried
Billet Sawn  Growth ring 45-90° to board face. Heart-split.
BM  Board Measure
Bow  When the centre of a board is raised higher than the ends when laying on a flat surface
Boule French term for a Through & Through log, used in UK timber trade
Brown Oak  Quercus Robur with fistulina fungus
Butt-jointed When two pieces of material are joined by simply placing their ends or side by side for gluing
Case Hardening  Tension-set/ Compression-set
Cats paw  Epicormic growths (shoots growing from a previously dormant bud on the trunk or a limb of a tree).
C Grading Coniferous Grading C16>C27 for strength.
CITES Convention of International Trade of Endangered Species
Cladding A building’s outer layer of either horizontal or vertical material meant to improve insulation and weather resistance
CND  Colour No Defect
Cross Cut Cutting to dead length
CTS  Cut to Size (to the nominal sizes required).
Cupping  A board in tension on one face
D Grading Deciduous Grading D20>D70 for strength
Dead Knots  Evidence of ingrown bark – unstable
DM  Decimetre – square area of a board
Durability A measure of durability of how long and untreated sample of a timber species will last before decay
FAS  First & Seconds (clean one face)
Fissure A drying crack usually along long pith/heart in dying
 Gate Parts _________________________________

HURR – The main vertical of the gate from which the gate hangs

HEAD – The second vertical

BACK – Top rail of the gate

SPLEATS – The remaining cross rails

BRACE – Strengthening rail built diagonally across the gate. SINGLE~CROSS(2 braces)~DIAMOND

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GIB Grown in Britain
Grain A term often misused – relating to all the axial elements running parallel to the edge of the board
FIN  Finish size
FE Feather Edged
FS  Fresh Sawn
FSC  Forest Stewardship Council
FOM  Free on motor. This term indicates the status of a product loaded safely onto the customer’s vehicle, but deemed ex-yard (ie: no longer on-site).
FSP  Fibre Saturation Point. When a tree is first felled, it is considered to be in the green state, and contains a very large amount of moisture. This moisture exists in two different forms: as free water that is contained as liquid in the pores or vessels of the wood itself, and as bound water that is trapped within the cell walls. It is only once all the free water has been lost that the wood will reach what is called the fibre saturation point, or simply FSP.
H/G Timber Homegrown timber – not imported.
Half a Knats 50% of a Knats (see Knats)
Half-lapped Where two pieces of stock, typically of the same thickness, have half of the material removed so that the two boards fit together with no added thickness at the joint.
Heartwood Inner rings inside the sapwood band
Heart Shake  A separation between adjacent layers of fibre, radial and due to shrinkage through seasoning or old age
Hoppus A measurement for logs or round timber to calculate the volume, or a tapered cylinder if temperate, or cylinder if tropical.
KD  Kiln-dried
Knats A very small measure (northern term).
Live Knots  Absence of ingrown bark – stable
M/C  Moisture Content
Merchantable  Can include knots and face checks, but constructionally sound
NHLA  North American Hardwood Lumber Association
NOM  Nominal size
Oak Grading For beams see BS5756
P/2/S  This refers to the board being planed on two faces
PAR  Planed on all four faces (from the nominal sizes)
PEFC  Programme for the Endorsement of Forest Certification
PTG  Planed, Tongue and Groove
PTGV  Planed, Tongue and Groove and ‘V’
Proforma  Payment prior to order being actioned
Quarter Boards/Quarter Sawn  These boards are radially cut which expose the medullary rays. It is rare for sawmillers to cut logs using this method, as it increases both waste and cost to mill, making the overall price increase substantially.
Ring Shake  Separation of one annual growth ring from another
Sapwood The outer rings of the log, this can be very visible in some species eg: Oak and Yew, but almost visibly non-existent in others eg: Ash and Sycamore
Scotia A concave moulding, especially at the base of a column
SE  Square Edges
Smidgeon Another small measuring unit, similar to Knats above (southern term)
1SE One square edge, one waney edge
Spp  Timber Species
Spring  Board laid flat but curved
Star Shake  Excessive cross-sectional drying in logs
STM  A term where the timber selector selects timber to cover the customer’s timber cutting list.
Tangential Boards These are boards produced from the outside of the log
Texture Fine grain > course grain
Tongue and Groove When boards are joined by means of interlocking ridges and hollows down their sides
T/T  Through and Through – A log sawmilled into plank and left with the bark edges on it
Twist  Propeller shaped board
Waney/Bevelled The sloped-off shape on the end of sawed timber (instead of square)
 

Weather-board 

A form of external cladding designed to overlap (unlike flush cladding). Particularly effective in damp or maritime climates where there is a risk from high salt-content spray. This can have a 1/S/E or square edge, usually fresh sawn if external cladding.
WE  Waney Edged – as T/T above
WRC Western Red Cedar