A guide to some of the words you may hear when utilising hardwood.
A
Air Dried
Timber left to season in the open air under cover.
See ‘Seasoned’.
Anti-graffiti
Resistant to minor purposeful damage.
Hardwoods will deter all but a committed vandal! Graffiti and Spray Paints will sit on the surface of the timbers as opposed to soaking in (including anti-graffiti paints, so don’t use them, they will cause maintance issues!)
Pen knives will scratch the surface, but will not cause permanent damage. Scratching can be sanded off, and the exposed layer will season back in with 3-6 months.
B
Baluster
The short posts or pillars that make up a balustrade.
They support the rail at the top and stand on the base at the bottom.
Band Sawn
Timber cut with a vertical saw.
Beam
A straight structural timber.
Acts primarily to resist non-axial loads.
Bearer
Heavy section timber which supports joists.
C
Character
The typical look, feel, behaviour the timber displays.
It can also refer to a grade when talking about Oak, and may mean that the timber has too much ‘character’ to be able to make the plain, clear, knot free grade that is often required.
Check / Checking
Separation of fibres along the grain.
Formation of a crack or fissure that does not extend through timber or veneer from one surface to the other. Can be caused by drying too quickly.
Cupping
When thin wide boards cup.
A warp across the width of lumber, usually with the bark side of lumber shrinking more than the heart side (or side closest to the center of the tree).
D
Density
A measurement of timber specification.
Varies depending on species and moisture content, see individual timber data sheets.
Dimensional timber
Wood that is the correct finished size.
See ‘Nominal Dimensions’.
Durability / Natural Durability
The resistance to fungal decay.
Five natural durability to wood-destroying fungi classes are recognised in BS EN 350-1 (see additional documents for details).
Dressed Four Sides
Dressed smooth suitable for joinery.
Timber machined to an even thickness and surface, more typically described as Planed All Round.
F
Finished Sizes
The sizes the piece of timber is machined to finish at.
Finished sizes have to be less (10mm) than the origin timber dimensions (nominal dimensions). So if the required finished size is 45mm, then the raw timber must be from 55mm to allow for 10mm of timber to be machined away.
Typically expressed in Metric (Millimetres).
Fresh Sawn / Green
Timber newly cut from the log, still in a soft state, it is high in moisture but evaporates most of that off as it is dried and hardens.
F
Fire Retardancy / Resistance
Ability to withstand heat or direct flame.
Hardwood timbers will only char, unless they are stoked they will not set alight like softwood and burn easily. The heat of a blowtorch is required to maintain combustion of the wood gasses.
Hardwood has minimal deformation during fire and it’s strength is not directly compromised by extreme heat, therefore risk of sudden failure is minimised.
Forestry
Also known as Woodland Management.
The management of land and trees with regard to protecting the natural woodland environment whilst facilitating forestry based industries.
G
Grade / Grading
Defining of timber in regards to particular qualities.
Timber grades vary depending on the strength, durability and other qualities of each wood species.
Grain Pattern
The visual finish shown on the timber surface.
Determined by the way a tree grows, different on every species. The main visual quality of a piece of wood is in it’s grain pattern, second only to Colour.
Gum Vein
A ribbon of gum produced in trees as a response to fire damage.
H
Hardwood
Wood that isn’t from a conifer tree.
Hardwood is generally from broadleaved trees.
Heartwood
The inner zone of wood.
In the growing tree, heartwood has ceased to contain living cells or conduct sap.
J
Joist
A particular use of timber lengths.
One of a group of light, closely spaced beams used to support a floor deck or flat roof.
K
Kiln Dried
The heating / baking of timber to remove moisture.
Kiln dried timbers are ideally used indoors so that the heat of a house will not cause the timbers to dry and shrink/crack further.
Kiln dried timbers used outdoors will swell as the timber starts to absorb moisture.
L
Lamination
Layered glued wood pieces.
Timber pieces glued together to make a solid thickness, width or length.
M
Moisture Content
Moisture contained in timber, measured as a percentage.
All solid timber has a moisture content and this is measurable to within a few percent. The moisture content of a timber changes due to a natural rate of drying once sawn, the mechanical drying process and in response to atmospheric conditions.
M
Moisture Movement
Dimensional change in timber due to moisture level change.
Dimensional changes occur when dried timber is subjected to changes in atmospheric conditions.
Moisture movement is a relative term and is classed as small, medium or large, and is not directly related to the initial shrinkage which occurs when green timber is dried.
N
Nominal Sizes / Nominal Dimensions
The raw timber sizes.
The original sizes of timber prior to finishing (see ‘Finished sizes’), typically expressed in Imperial (inches).
P
Pinhole
A tiny hole in timber caused by insects.
Pinworm Beetles or Ambrosia Beetles bore into wet timbers and feed upon the mould fungus which grows on the damp tunnel walls. As the timber dries out, the fungus stops growing and the beetle starves to death.
Pin Hole does not affect the strength of the timber, the borer only eats the outside of the wood, it does not normally go deep into the timber. When timber is weathered pinhole typically cannot be seen, more noticable in freshly planed timber. Pin Hole is NOT a defect, see Pinhole Information Sheet for details.
Post
Upright often supporting a structure.
P
Planed All Round (PAR)
A finished wood specification.
Meaning planed on each surface apart from ends (4 sides), usually to specified dimensions, i.e. the required finished sizes.
Similar to PSE, typically still square but not necessarily. Some timber yards will use PSE and PAR interchangeably but they’re not exactly the same thing.
Planed Square Edge (PSE)
A finished wood specification.
This means the wood has a smooth, planed finish on all sides (not the ends) and all the edges are square (90°).
Profile
The sectional outline of the timber.
The shape you see if you sliced across the grain.
R
Regularised
Planed to the correct size.
Generally not as smooth as PAR / PSE.
Resin
Honey-like subtance that exudes from some Hardwoods
when freshly machined.
Exudes along fine lines in the timber, then cristalises to a chalky/ crumbly white deposit. Won’t keep re-occurring. Brush, sand, dust, wash it off and it will weather once again.
Rough Sawn Timber
Timber straight off the saw.
The timber is roughly sawn to roughly the right size and will normally have a rough surface finish, and hasn’t yet been planed.
S
Sadolin
Water based low build stain.
A protective coating, generally applied for short-term protection of timber products during shipping and installation. Allows the timber to breath and weather naturally.
It will not flake or crack like solvent based varnishes, gloss or paint.
Sap
Exudes from Softwoods.
A runny, sticky, sweet smelling substance. Will keep occurring.
When a tree is alive, sap carries nutrition from the roots to all areas of the tree, through its network of trunk and branches. When the tree has been cut, the sap is no longer needed and kiln drying the wood will result in the substance becoming crystalised; forming a resin.
When there are changes in humidity or temperature, it can be perfectly normal for small amounts of this resin to ooze from the timber. The resin is not harmful at all and can be easily removed, scrape off or wash off with warm water and a deck scrub.
After the first year of use, it is unlikely that any further resin will come out of the timber.
Sapwood
The outer zone of wood.
The part in the growing tree that contains living cells and conducts sap.
Seasoned / Air Dried
Timber left to season in the open air under cover.
This is to reduce the moisture content within and so reduce the chance of movement once in use.
Timbers are stacked up outside, under cover from rain, for 6 months to 5 years, dependent upon how seasoned. General rule of thumb for Hardwood air drying is 1 year per inch of thicknes.
Section / Section Size
Short for cross-section.
A 90 degree slice across a width, as opposed to down a length, with Section Size measuring the dimensions across that cut.
Service Life
Years of anticipated durability of the timber in certain situations.
From a TRADA test for durability class involving timber being buried in the ground and measured the susceptibility to infestation and rot. It is not a measure of durability for typical uses.
Shake
Fine hairline crack.
Separation of fibres along the grain in drying timber, splits in the structure of the wood, caused by growth defects or shrinkage stress.
Shelling
Lifting of the timber along the grain.
Shrinkage
See Moisture Movement.
Can be estimated depending on species.
Silver Down / Silvering
The colour change occuring in drying exposed timber.
Timber left unfinished externally weathers as it dries and hardens whilst exposed to the elements. Over a period of time the original timber colour will fade to a beautiful grey, silvery colour. To prevent this the timber must be protected with an external finish of some kind on a regular basis, but this is not requried to aid the durability of hardwoods it is surface appearance only.
Softwood
Timber from a conifer tree.
Trees that have needles and make cones, where hardwood is from broadleaved trees.
Source / Origin
Where the timber grows.
Where we source it from, e.g. ‘SE England’
Surface Checking / Cracking
Grain lines open up.
Species
Common Name and the Biological Name of the tree.
Split
Separation of fibres along the grain forming a crack
A split is a crack or fissure that extends through timber or veneer from one surface to the other.
Strength
Assessed mechanical strength of timber.
Assessed in relation to resistance to shock, axial compression & tension, resistance to bending and elasticity/deflection.
T
Tannins / Quertannic Acid
A fibrous pigment that leaches out of timber.
Not to be confused with Stain, Sap or Resin
Some timber species contain Tannin, Quertannic acid, that is corrosive to Ferrous metals, and can leave black blue stain on the timber but ironically this is part of what makes the timber species more durable.
It only occurs in early stages of freshly machined components, and will not last for longer than a month or two. Weathering will naturally remove it within a couple of months, or use warm water, household bleach and a deck scrub.
Texture
Surface feel of the timber.
Hardwood surface texture is classified as fine, medium or coarse.
T
Timber Type
Hardwood or Softwood depending on species.
Timber Properties
Timbers have specifications that vary by species.
Movement/stability, durability, strengths, density, there are particular values of different timbers that are relevant to the appropriate uses. Datasheets on our main timbers are available.
Treatability
How easily timbers can be penetrated with preservatives.
TRADA states that timber species rated as durability Class 3 or better can be used without treatment if non-durable sapwood is excluded.
W
Wastage
The amount timber left after conversion.
The ‘unusable’ timber separated from the usable timber.
Wood Worm
The larvae of a fly that lives off wood.
Not to be confused with Pinhole. Woodworm is more typical for indoor furniture and doors, particularly when they’ve been exposed to leaks or a damp environment.
W
Workability / Working Qualities
How easy a species is to machine for the required use.
Whether it is easy or difficult with hand tools or machine tools, and is usually related to grain patterns, hardness, acid or resin content. Generally with dry hardwoods the more wavy grained and knotty they are, the more tricky they are to work. Fresh sawn timber is always softer and therefore easier to work.
Often classed as good, medium or difficult. A difficult classification indicates that particular care should be taken in machining to achieve an acceptable surface finish.
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