What is Hardwood?
Hardwood is an organic, often visually attractive material that comes from the trunks and branches of trees.
It is used in the construction of many everyday items such as furniture, doors, the framework of some buildings, musical instruments, flooring, tool handles and even the fascias in some (usually expensive!) cars.
Generally, the long fibres of hardwoods are densely packed, making the wood harder and so suitable for applications which call for fairly tough surfaces.
While hardwood is usually more expensive than softwood and often has a more complex and aesthetic grain structure, softwood scores for some applications because of its comparative lightness, lower cost, and the fact that it’s generally easier to cut and shape.
What is Hardwood Used For?
Hardwood is used for tables, chairs, flooring, turned wooden bowls and lampstands, tool handles, construction work that needs to last (beams, joists and frames), carved ornaments, pianos and other musical instruments – the list seems endless.
Because of the relatively high cost of hardwood, and the fact that some hardwoods are becoming scarce due to over-exploitation in some parts of the world, many “hardwood” items, particularly furniture, are in fact just a thin veneer of hardwood bonded to a core of softwood or medium-density fibreboard (MDF).
Because the veneer is used on all the visible sides and edges, the impression is that the product is made entirely of expensive hardwood.
An advantage of veneered wood is that it is usually less likely to split, crack or warp over time than pieces made from solid wood.
How can you tell if the furniture is veneered or solid wood?
You can usually tell by checking for end grain. For instance, a tabletop will have two long edges parallel with the direction of the wood’s grain.
The other two, usually shorter, ends will have end grain, where the grain has been cut laterally. It looks like a matrix of minuscule dots and sometimes shows parts of the shaded rings – the “growth rings” – of the tree it came from.
Look where you would normally expect to see end grain on a piece of furniture. If the grain runs in lines along the edge, the furniture is veneered. If it looks like end grain, it’s solid.
How is hardwood formed?
As the trunk and branches of a tree grow bigger, the long, narrow inner cells they are composed of deteriorate and die, leaving behind just the cell walls, which become what is known as the heartwood.
The living part of the trunk or branch is the part known as sapwood, just inside the tree’s protective covering, the bark. The sapwood continues to transport nutrient from the ground to the higher reaches of the tree, while inside the deadwood continues to expand with each successive growing season.
The heartwood is what – after being sawn and planed – becomes the hardwood timber that can be used in literally thousands of different ways.
After felling and usually (but not always) after being cut into large, initial shapes, hardwood is either left to dry naturally over months or even years. Another alternative is that the hardwood is quickly dried in a purpose-built oven known as a kiln which is a lot quicker process.
What types of tree does hardwood come from?
Hardwoods come from broad-leaved deciduous trees – the type, such as oak, ash and beech, that bear flowers in spring or summer, develop some form of fruit, then lose their leaves in the autumn.
Softwoods, on the other hand, come from evergreen, coniferous trees, typified by fine, needle-like leaves.
So how hard is hardwood?
Some hardwoods are not hard. Balsa wood, known for its lightness and ability to bend – making it useful for making model aeroplanes – is a good example of a soft hardwood.
However, some woods, like lignum vitae, are so dense – and therefore hard – that they sink in water. This type of wood is used for tools, such as wooden hand planes, that need to be particularly tough and enduring.
It’s also true that some softwoods can be quite hard, but generally speaking, hardwoods are hard and softwoods are softer.
What sizes of hardwood are available?
Random is the key word
Hardwood can be very different from softwood when it comes to size. The key word here is “random” because hardwood trees generally don’t grow straight (their crookedness is what often gives them attractive, swirly grain), and the width of trunks and branches varies considerably.
While many timber merchants do have some off-the-shelf sizes for you to choose from, they usually also provide custom sizes and can be very helpful in meeting unusual requirements.
However, you will most likely have to pay for any wastage when rough-sawn hardwood is cut to a particular size for you.
Rough-sawn or planed hardwood
You can buy hardwood rough-sawn or prepared to some extent. PSE (planed square edge) hardwood is planed on one side (which provides a reference for planing and squaring up the other sides). PBS (planed both sides) is planed on opposite sides, while PAR (planed all round) is planed on four sides (but leaving the short, “end grain” ends unplaned as length is the dimension that is most likely to change when the wood is cut to fit into a project).
Why your piece of wood might be smaller than you think?
If you order hardwood in specific sizes and it’s prepared to some extent (planed on one or more sides), you may find that your wood is actually smaller than quoted.
This is because the sizes used in the industry are often based on rough-sawn wood, which loses a little of its thickness or width, or both, when it is planed.
Characteristics of hardwood
Hardness and load-bearing ability
Firstly – and perhaps most obviously – most hardwoods are hard and strong, which makes them suitable for applications where the wood is likely to get knocked about – such as tool handles, cricket bats and mallets – and where load-bearing is important.
Where endurance is an important factor, hardwood is again the natural choice.
The range of natural hardwood colours – including reds and browns of different intensities and shades, practically black and almost white – provides a wide choice when it comes to flooring, furniture, panels, window frames and the internal and external walls of buildings.
Another aesthetic consideration is grain, the often linear but sometimes twisting, swirling visible lines in the wood’s surface resulting from the dried out, linear cell structure of the tree’s heartwood. Some hardwoods are particularly sought after because of their intricate grain structure.
Hardwood BS Grading
Timber for building is graded according to British Standard (BS) EN 338:2003 Structural Timber, which gives six grades for hardwoods, from D30 up to D70. The numbers represent the characteristic bending stress for each strength class.
The BSI Kitemark is a registered trademark of The British Standards Institution and the use of it is with kind permission.
Advantages of Hardwood
Hardness and strength
Attractiveness – colour and grain
Better fire resistance (although burns longer and provides more heat than softwood when used as fuel)
Disadvantages of Hardwood
Generally more difficult to cut and shape