Jargon Busting #
- When it comes to getting started with a DIY project, you can have all the right foundations (money, time, tools, etc.) but, when you go to buy the necessary timber, find yourself lost in a sea of industry terms.
- This is often a result of a lot of jargon used by sales representatives as casually with regular customers as they would with industry professionals or workers on the yard.
- Even the strangest abbreviations are pretty simple to break down, so don’t worry about it – we’ll soon have you talking SWE’s, PARs and all the other terms like a professional.
Off saw refers to the first finish of the timber – how a plank looks when it comes straight out of the mill, having been passed over the saw just once. This slightly rougher finish is perfectly fine for a wide variety of outdoor construction projects, such as cladding a house, making a shed, or practical outdoor crafts that are designed more for longevity than style.
Planed All Round (PAR) #
When an off saw plank needs to be polished up a bit, it’s passed through a planing machine. This machine takes off large sections of the surface level of the wood, removing inconsistencies and the rougher texture you get as a result of the O/S method. While you can expect PAR wood to be relatively smooth, there’s always a chance that the procedure may tear out sections of the plank, generally where the grain of the timber pulls in the opposite direction to the machine. You should also note that planed all round wood still isn’t sanded wood, so you should specify separately if you want the wood to be sanded, for an entirely smooth finish.
Planed Square Edge (PSE) #
Unlike a PAR plank, which is planed everywhere, a PSE plank is only planed on one side. This might be useful if you want to lay down some floorboards, as PSE wood is generally cheaper than PAR wood, but you should avoid it if more than one side of the wood will be visible.
Single Waney Edge (SWE) #
This finish is usually one you might prefer on a hardwood like oak, elm, or beech (although Douglas fir, a softwood, can benefit from it as well). Basically, single waney edge means that one side of the board is left ‘natural’, which could mean any number of things depending on your preference. You might leave the bark of the tree on the waney edge, or just leave the knots and natural grain exposed. The edges that aren’t the waney edge are then cut straight, to a more machined standard.
Double Waney Edge (DWE) #
As you might imagine, this is a lot like the single waney edge, except that two sides of the board are left with a more natural-looking appearance, while the other two are cut to a more machined standard. You might choose this if you want a very natural-looking piece of furniture, such as an oak coffee table.
When you see this term used to refer to wood, it just means: ‘What are you planning to use the wood for or in?’ Different varieties of wood work better in different scenarios, and anything from the size of the construction, how much load it should be expected to bear, what finish you want on it, or even the climate conditions can affect what kind of wood will work best for that application.
Air Dried #
Air drying is a drying process generally used on hardwoods. Usually, a hardwood log is cut into boards which are then stacked on top of each other, with pieces of wood separating the logs. This lets air flow between the boards, drying them naturally via a process that can take several years. This form of drying is useful because it reduces the moisture level in the boards by a substantial amount. Trees naturally have a great deal of moisture in them, and letting the moisture stay (unless you want it green) is often bad for the strength of the wood. This is the first stage in preparing hardwood for indoor use – for instance, making furniture.
Kiln Dried #
Wood that’s been air-dried for a while can then be placed into a kiln. Much like a kiln for making clay, a wood kiln is an enclosed, heat-controlled oven that allows moisture inside the timber to slowly evaporate. In some cases, kiln drying can reduce the moisture levels in wood to roughly 8%, which is a good reduction on top of what air-drying can achieve (air-dried wood tends to have moisture levels of about 20%). Once it’s out of the kiln, that wood can be stacked in an air-drying shed, and then finally processed for the customers.
Sometimes you might want wood that’s not been air dried or kilned in any way. While both processes are useful, they’re not always necessary for every project, and can add time and expense. For instance, if the wood you’re working with is going to be exposed to a lot of water (perhaps you’re building a slipway for a boat), you can just ask for the wood to be green, because it’ll hold up fine without kiln drying.
Linear Metres #
A common term in the construction industry, a linear metre is the equivalent of one standard metre but measured in a specific direction. Unlike a square metre, which describes a square of the material whose sides all measure 1m in length, a linear metre describes a 1m length of that material – for instance, ‘a cable measuring 2 linear metres’.
m2 and m3 #
Often, you’ll see wood for sale measured in m2, or metres squared. A square metre is, basically, anything that’s one metre long and one metre wide. The calculation to work out a square metre is length x width, so a piece of wood that’s five metres long and three metres wide is 16 m2.
Sometimes, especially for larger construction pieces, you might see it referenced in metres cubed (m3) instead. (You sometimes also see it if the piece is load-bearing, and so its volume is important.) Metres cubed is much like metres squared, but it takes the wood’s height into consideration as well. To calculate m3, you figure out length x width x height. So, a piece of wood that’s five metres long, three metres wide and six metres tall is 90 m3.
Usually connected to a number of central beams, joists provide the fundamental support to the floor that rests on top of them. In traditional timber-framed households, joists tend to either be single floor (one set which carries both the floor and ceiling) or double floor (two sets, one for the floor and one for the ceiling). Often, roof joists are connected to a central beam in the ceiling, called a summer beam.
Cladding Batten #
Timber battening is an architectural feature in which boards of wood (battens) are laid out with a narrow space between them, to aid in ventilation. Cladding battens are battens that have been especially treated for exterior work (humidity, water resistance, etc.) and attached to the exterior of a house to function as cladding.
Counter Batten #
Regular battens tend to be installed and spaced vertically, as you can see in the board structure of most wooden houses. Counter battens are additional battens that have been fitted horizontally, to further aid with insulation and environmental protection.
Fascia Board #
A rarely appreciated but vital element of home construction, a fascia board is a long board attached at the point where a house’s roof meets its walls. Given its central function in supporting the bottom row of roof tiles and the house’s guttering system, choosing the right fascia board is a vital part of home construction.
In timber-frame house construction, a purlin is a large support beam, often attached to the central rafters, that aids in the wider pattern of roof support.
Sapwood and Heartwood #
Sapwood refers to the most immediate ring of wood underneath the bark, which surrounds the deeper core of heartwood. Sapwood tends to be lighter in colour than heartwood, as its cells aid in the transportation of water from the tree’s roots to its branches, and thus lack the dark-staining chemicals of heartwood. Heartwood also tends to be stronger and denser by comparison, although there will always be less heartwood than sapwood.
Live and Dead Knots #
A ‘knot’ in wood is an imperfection in the wood’s grain, which is usually formed when a branch breaks off from the main tree and exposes the wood underneath to the elements. While knots can often be a visually pleasing part of a wooden product, they can also introduce difficulties in construction (especially in wood varieties that are particularly knot-prone, like Douglas fir or larch).
Grain Raising #
‘Grain raising’ is a problem that can arise when coating wood using a water-based coating. In order to avoid grain-raising, spray the wood with water, allow some time for the wood to dry, then sand it lightly to remove the raised grain. For more, see this video from high-quality coating manufacturer TreaTex: Treatex Colour Tones – popping the grain
‘Checking’ in wood (narrow separations across the grain) can occur in the drying process for any number of reasons, mainly the wood species, moisture content, or the storage method for the wood. Checking may look worrying, but it’s actually good for the product as a whole, as it helps release structural tensions and pressures in the wood.
‘Deciduous’ refers to trees that shed their leaves in the winter. Their counterparts, evergreens, keep their leaves all year round.
Any trees that carry pine cones are called ‘conifers’.